The effect of different oxygen and salinity levels in the rooting media on the growth of cotton (Gossypium barbadense and G hirsutum L )

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(1)BAC. El documento fuente se encuentra en La Biblioteca Agropecuaria de Colombia. M O D U L O D I G I TA L. ELEMENTOS BIBLIOGRAFICOS AUTOR (ES): Owen Bartlett, E.J. AUTOR (ES) CORPORATIVO (S): University of California, Riverside (Estados Unidos). TITULO: The effect of different oxygen and salinity levels in the rooting media on the growth of cotton (Gossypium barbadense and G. hirsutum L.) LUGAR DE PUBLICACION: Riverside (Estados Unidos) AÑO DE PUBLICACION: 1977 PAGINAS: 216 p..

(2) UNIVERSITY OF CALIFORNIA RIVERSIDE. J. .. The Effect of Different Oxygen. and Salinity Levels. In the Rooting Media on the Growth of Cotton (Gossypium barbadense and b. ursutum L.). A Dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Soil Science. Eric Jose June, 1977. Dissertation Committee: Professor Lewis 11. Stolzy, Chairman Professor Merrill R. Kaufmann Professor Frank Tm Bingham.

(3) The dissertation of Eric Jose Owen-Bartlett is approved:. University of California, Riverside June, 1977.

(4) .. ACKNOWLEDGEMENTS. 1 am deeply grateful to my major professor, Dr. Lewis H. Stolzy, for his friendship, advice throughout my Ph.D. program, and his guidance in the preparation of this dissertation. 1 also express my appreciation to Drs. II. R. Kaufman and F. T. Bingham as members of my committee; for their valuable suggestions during my studies and for their constructive criticism of the manuscript. 1 would like to acknowledge the following people:. Dr. C. K;. Labanauskas and Mr. M. F. Handy for the training and use of the equipment for plant analysis; Dr. Burl D. Meek for his generous cooperation and help in the field experiment at Brawley; Dr. C. K. Huszar and Mrs. Caro1 Adams of the Statistics Department for their valuable assistance in the statistical analysis of the data; Ted Szuszkiewicz and Alan Eckard who showed me the use of the equipment for these studies; Ray Sharpless, Dean David and Gary Lopatynski for their help; and Louise DeHayes and Cheryl Alms for the final typing of this dissertation. 1 am deeply grateful to the entire staff and friends in the Department of Soil and Environmental Sciences for the excellent assistance received during my Ph.D. program. 1 express my gratitude to the International Development Research Center of Canada for providing financia1 support for my graduate studies and to the "Instituto Colombiano Agropecuario", ICA, for selecting me for this study leave. . iii.

(5) Last, but not least, 1 will like to express my deep appreciation to ny wife, Martha Lucia, and my children, Andy and Adriana, for their help, understanding, encouragement and love that helped me conclude ny graduate program.. iv.

(6) ARSTRACT OF TlIE DLSSERTATION. THE EFFECT OF DIFFERENT OXYGEN'AND SALINITY LEVELS IN THE ROOTINC MEDIA ON THE GROIJTH OF COTTON (Gossypium barbadense and d. hirsutum L.). Eric J. Owen-Rartlett Doctor of Philosophy, Graduate Program of the Department of Soil and Environmental Sciences University of California, Riverside June 1977 Professor Lewis H. Stolzy, Chairman. Cotton is a very important crep not only due to the high f!.ber yields, but also to the large amounts of oil extracted from the seed, the high protein content of the cotton seed meal, and the large number of unskilled labor needed, to pick it in developing nations where there is a very high unemployment rate. Cotton is relatively tolerant to high salinity levels but susceptible to low oxygen contents in the soil.. The object of. this research was to find the most resistant variety of cotton to low concentration of oxygen and high levels of salinity and how they affect the physiological processes, growth and nutrient uptake. To study the influente of oxygen and salinity on the germination of 10 varieties of cotton, two experiments were performed.. One. experiment treating the soil with four oxygen levels (0, 4, 10 and 21%) V.

(7) and the other treating the soil with Eour salinity levels (0, 5, 10 and 20 mmhos/cm). The four most tolerant varieties to low oxygen were T-4852, Stoneville 213, Acala 1517-70, and the Eour most tolerant vacieties to high salinity were Stoneville 213, Acala 1517-70, San Joaquin 2 and Pima S-4. Using results Erom the Eirst two experiments on germination, two more experiments were conducted. influente processes,. These studies showed the. of Low oxygen and high salinity on the physiological growth and nutrition.. The varieties used were Stone-. ville 213, Acala 1517-70, T-4852 and Pima S-4. The decrease in oxygen caused a significant decrease in leaf conductance, xylem potential and water uptake; seed cotton, root weight, leaf area, total dry weight, leaf area, stem weight, root depth, and stem height.. A decrease in oxygen'caused a decrease. ín the root concentrations of Zn, K, Cu, Mg; in the stem concentrations of B, P. Zn, Ca, K, Mg, Cu; in leaf concentrations of N, Ca, B, K, W; and a significant decrease in total uptake of Na, Mn, Fe, N, Zn, Cu, B, Ca, K, P, flg. The decrease in oxygen caused a significant increase in the root concentrations of B, Fe, Na, Mn; in the stem concentrations of Fe, Mn, and Na; in the leaf concentrations of Fe, Na, Mn. Tolerance to low oxygen is based on the property of roots to penetrate deep into the soil profile under anaerobic conditions and to tolerate high uptake of Mn and Fe by roots and the high storage capacity of Na in the roots and stems. vi.

(8) The highest yielding variety was Pima S-4 followed by Stoneville 213, 'Acala 1517-70 and T-4852. The increase in salinity caused a significant decrease in xylem potential, osmotic potential, leaf conductance, and water uptake; roots, stems, leaf weights, total dry weight, seed cotton, root depth, stem height and leaf area.. Root concentration of K, Ca, Fe decreased. as well as a decrease in the stem concentration of P, and in the leaf concentration of B and P with increased salinity. The increase in salinity caused a significant increase in root concentration of B, Zn, P, N, Mn, and Na; in the stem concentration of Ca, N, Na and Mn; and in the leaf conductance of Ca, Zn, Fe, N, Mn and Na. The highest yielding variety was Pima S-4 followed by T-4852, Acala 1517-70 and Stoneville 213. Variety Pima S-4 was used to study interactions of low oxygen and high salinity ín the rooting media on the physiological processes, growth and nutrition.. The same trends were found as in the oxygen. and salinity experiments, and the interaction of oxygen with salinity was highly significant. Variety Stoneville 213 was used to observe the effect of three water table depths (30, 60 and 90 cms) on the physiological processes, growth and nutrition on cotton in a field experiment. The decrease in water table depth caused a significant decrease in leaf conductance, seed cotton, leaf area, stem weight, total dry weight and leaf weight.. A decrease in oxygen also caused a decrease. in stem concentrations of Ca, Fe, K, Cu, Zn and N; in leaf concentrations of Mn, Cu, Ca, N and K, and a significant decrease in total.

(9) LIST OF TABLES. Page. Table 1.. 2.. 3.. 4.. 5.. 6.. 7.. 8.. 9.. 10.. Influente of soil oxygen on the relative percent emergence and relative days to first emergence of ten varieties of cotton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11. Combinations of air and nitrogen gas to obtain the desired oxygen treatments and ODR resulting from the treatments in the soil . . . . . . . . . . . . . . ..*................ 34. Influente of soil oxygen treatment on the diurna1 pattern of leaf conductance on the bottom and top of the leaf of four varieties of cotton determined 45 days after germination . . . . . . . . . ..".................. 35. Influente of soil oxygen on physiological processes (leaf conductance, xylem potential, osmotic potential, and water used) with four varieties of cotton at two stages of growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37. Influente of soil oxygen on plant growth (root, stem and leaf) and yields (seed cotton) for four varieties of cotton . . . . . . . . . . . . . . . . . . . .."........................ 42. Influente of soil oxygen on the concentration of N, P, Ca, Mg, K and Na in the root, stem and leaf, and the total uptake of these elements by four varieties of cotton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 48. Influente of soil oxygen on the concentration of B, Zn, Mn, Cu and Fe in the root, stem and leaf, and the total uptake of these elements by four varieties of cotton .*............................................ 56. Influente of soil salinity on the relative percent emergence and relative days to 50% emergence on ten varieties of cotton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 81. Influente of soil salinity on the diurna1 pattern of leaf conductance on the bottom and top of the leaf for 4 varieties of cotton at 50 days after transplanting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 103. Influente of soil salinity on leaf conductance, xylem potential and osmotic potential at 71 and 99 days after transplanting and water use on four varieties of cotton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..<....".. 105. xii.

(10) LIST OF TABLES (continued). Page. Table 11.. 12.. 111. Influente of soil salinity on the concentration of N, P, Ca, Mg, K and Na in the root, stem and leaf, and the total uptake of these elements by four varieties of cotton . . . . . . . . . . . . . . . . . ..*................ 115. 13.. Influente of soil salinity on the concentration of B, Zn, Mn, Cu and Fe in the roots, stem and leaves and the total uptake of these elements by four varieties of cotton . . . . . . . . ..*........................ 123. 14.. Influente of soil oxygen and salinity treatments on physiological response, leaf conductance, xylem potential, osmotic potential and water use of Pima S-4 variety at tu0 stages . . . . . . . . . . . . . . . . . . . . . . . .. 15.. '. Influente of soil salinity on the production of root, stem, leaf, total dry weight and seed cotton of four varieties of cotton .."................................. 16.. 17.. 18.. 19.. 20.. 145. Influente of soil oxygen and salinity on plant growth (root, stem and leaf) and yields (seed cotton) of cotton variety Pima S-4 . . . . . . . . . . . . . . . . . . ..".......... 149 Influente of soil oxygen and soil salinity on the concentration of N, P, Ca, Mg, K and Na in roots, stems and leaves and the total uptake of these elements of cotton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 154. Influente of soil oxygen and soil salinity on the concentration of B, Zn, Cu and Fe in roots, stems and leaves and the total uptake of these elements of cotton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 162. Influente of the depth of the soil water table on the electrical conductivity, pH and percent soil moisture of the soil determined at the initiation and termination of the experiment . . . . . . . . . . . . . . . . . . . . .. 190. Influente of the depth of the soil water table on the oxygen content, oxygen diffusion rate and redox potential of the soil determined 80 and 100 days after planting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 192. Influente of the depth of soil water table on the leaf conductance, xylem potential and osmotic potential determined 80 and 100 days after planting . . . 194 xiii.

(11) LIST OF TABLES (continued). Table. Page. 21.. Influente of the depth of the soil water table on the stem weight, leaf weight, leaf area, total weight and seed cotton production . . . . . . . . . . . . . . . . . . . . .."......... 199. 22.. Influente of the depth of the soil water table on the concentration of N, P, Ca, Mg, K and Na in the stem and leaf and the total uptake of these elements by cotton variety Stoneville 213 . . . . . . . . . . . ..'........... 200. 23.. Influente of the depth of the soil water table on the concentration of B, Zn, Mn, Cu, Fe and Cl in the stem and leaf and the total uptake of these elements by cotton variety Stoneville 213 ,........................ 201. xiv.

(12) LIST OF FIGURES. Page. Figure. 1.. Experimental plot showing the layout of the tile drainages, treatments and instruments . . . . . . . . . . . . . . . . .. xv. 184.

(13) GENERAL. INTRODLJCTION. The importance of cotton production along with increased production of this crep on saline and sodic soils makes it necessary to determine the most tolerant varieties to low oxygen content in the soil.. It is also necessary to find varieties tolerant to high. levels of salinity and to show how these two factors affect yields.. These object-ives were accomplished with a series of experiments planned and executed according to a predetermined sequence which were as follows:. i) two gerzination experiments in a growth chamber,. ii) three growth experiments to first bol1 setting in a greenhouse, and iii) one growth experiment to first bol1 setting in the field. The first set of experiments was cotton seed germination, conducted simultaneously in the growth chamber.. The objective was to select. the two most tolerant varieties from each experiment as to low oxygen and high salinity conditions.. The oxygen experiment is part of. Study 1 with Experiment 1 on germination in the chamber and Experiment 2 on growth and cotton yield in constant temperature tanks in the greenhouse.. Study II was similar to Study 1 with Experiments. 3 and 4 on salinity.. Once thesc four varieties !two from each experiment) were selected, two more experiments were conducted using these four varieties. These experiments were concerned with the effect of low oxygen and high 1.

(14) 2 salinity ín the rooting media on physiological process, growth factors and nutrient uptake.. The oxygen experiment is also part of Study I. and is described in Experiment 2.. The salinity experiment is part. of Study II and ís described in Experiment 4. From Experíment 2, one variety most tolerant to low oxygen conditions ín the rooting media was selected and from Experiment 4, the variety selected was the most tolerant to high salinity.. The Pima S-4. variety was the most tolerant of low oxygen and high salinity conditions and so was used in Experiment 5 to study the interaction of these two variables.. Study III Experiment 5 was designed to measure the inter-. action of low oxygen and high salinity on physiological process, growth factors and nutrient uptake. Due to local regulations in the Imperial Valley of California ond other reasons, Pima S-4 was not used ín the field experiment which ís Study IV, In Study IV the effect of three water tables on the oxygen condition of the soil and its effect on physiological processes, growth factors and nutrient uptake was studíed on cotton variety Stoneville 213. To facilitate the presentation of this Ph.D. thesis material, each experiment was considered separately except for the introduction. There will be one introduction for each study instead of each experiment..

(15) Study 1 - Oxygen. THE EFFECT OF DIFFERENT COMBINATIONS OF OXYGCN LEVELS IN THE ROOT MEDILJM ON THE CROWTH OF COTTON (Gossypium barbadense AND G. hirsutum, L.). L.. INTRODLJCTION. Cotton is one of the world's leadíng fíber crops which produces a large economical return to the farmer.. It also employs a large. number of field workers (especially where cotton is picked by hand) solving in part the unemployment problem. Cotton generally suffers under conditions of poor aeratíon due to the type of root system which is a main tap root that goes deep into the soil profile.. Conditions of poor soil aeration are found in soils. with high clay content,. and with more than 15% exchangeable sodium.. The excess sodium causes dispersion of clay whích reduces the diffusion of aír by forming a soil crust.. Poor aeration is also caused. by puddling of the soil, poor draínage and high rainfall. aeration ís a very important factor in plant growth. the growth of many plants in two main ways:. Soíl. It can affect. i) directly on the. physiological activities of the plant, and ii) indirectly by affecting the soil constituents such as Fe, Mn, N, S, and organic matter which in turn influentes plant growth. The direct effect is due to the consumption of oxygen and production of carbon dioxide by aerobic respiration.. Respiration is not. only for higher plants but also for soíl microorganisms.. For maximum. respiration, most hígher plants need an optimum concentration of 3.

(16) 4 oxygen and a Low concentration of carbon dioxide.. If oxygen levels. are inadequate the roots will not develop normally causing reduced growth with less water and nutrient uptake'and as a consequence, less top growth.. The lack of oxygen also affects germination by. increasing the days to first germination, and thus exposes the seeds to soil conditions for a longer time which reduces germination. Plant susceptibility to poor aeration is presumed to be varietydependent.. The objects of this research were to:. i) select the most. resistant variety to low concentrations of oxygen; ii) determine the effect of low oxygen on emergence, the physiological processes such as leaf conductance, osmotic potential, xylem potential and transpiration and on nutrient uptake and how these processes affect plant growth and yield.. A general procedure for Experiments 1 and. 2 are briefly described in the following paragraphs.. Experiment 1.. A selection of four varieties of cotton was made. from eight commercial varieties grown in California and from two other varieties now being tested.. The selection process was based. on percent emergence and days to emergence.. Due to the large number. of varieties available in this experiment, it was impossible to obtain cotton yields at different oxygen levels for al1 varieties because of the large number of treatments involved. The process of elimination was based on the fact that the first stage of plant growth is germination.. If seeds have low emergence, there would. be poor stands and therefore low yields. Wanjura,et al. (1969) showed that time of emergence is a good indication of a cotton plant's.

(17) 5 vigor and potential yielding ability,.. Plant survival and yield. was more closely correlated with emergence time than with germination percentage.. The selection of the two best varieties from a total. of ten in two emergence experiments (salinity and oxygen) were used in a later experiment.. Experiment 2.. The selection of one variety of cotton from a total. of four obtained from this experiment will be based on the best relative yields;. The individual effect of different levels of oxygen. on growth, yields, physiological processes, and nutrient uptake will be studied on the four cotton varieties..

(18) Experiment 1:. The effect of different oxygen treatments on the emergence of ten varieties of cotton (Cossypium hirsutum - - - and G. barbadense L.). LITERATURE REVIEW. The process of seed germination is energy consuming and depends on the respiration of the seed.. Low concentrations of oxygen cause. the formation of fermentive products such as ethanol and lactic acid. Accumulation of these products in the seed reduces seed germination and seedling growth (Dasberg, et al. 1966).. Cermination of seeds in. artificially aerated soils (Hunter and Rich, 1925) was faster, the total number of seedlings emerging was greater and better developed than in a non-artificially aerated soil.. Oxygen dissolved in the water and. used by the germinating seeds accounts for only a maximum of 0.05% of the total oxygen requirement of wheat during the first 24 hour period of germination.. Therefore, most of the oxygen needed during germination. moves to the seed by the process of diffusion through the water film covering the seeds (Dasberg and Mendel, 1971). Baver and Farnsworth (1940) using sugar beets in northwestern Ohio found that the percent loss in stands was influenced by aeration of the soil.. Hydration of seedlings was more sensitive to change in. moisture tension in the presente of 21% oxygen than it was for lower levels of oxygen (Cingrich and Russell, 1956). Concentrations of oxygen less than 5% delayed germination of wheat and increased the day to first germination (Aceves-Navarro 1974). Winter wheat germinated at nearly 0% oxygen and showed maximum emergence 6.

(19) 7. at 10% oxygen.. Emergence and growth correlated better with the oxygen. content in the soil air than with the ODR measured with the platinum microelectrode (Kaack and Kristensen, 1967).. The decrease in the. germination rate of wheat at higher water contents of sands was paralleled by a lowered oxygen diffusion rate (ODR).. A decrease in. germination was found to occur only at ODR value below 20 x 10W8g cm -2 miri '. for Aryzopsis holeiformis..

(20) MATERIALS AND METHODS. To study the influente of different oxygen levels on the emergence of cotton, twenty seeds of each variety, ten in all, were sown one cm deep in a krilium treated Yo10 silt loam.. Enough water was. applied to obtain a soil water potential of -0.1 bars. used for each oxygen level.. A tray was. Trays were covered with transparent. plexiglass and sealed with inlet and outlet for the oxygen treatments. Different oxygen treatments were obtained by combining air and/or M2 gas mixtures which flowed through water bottles to obtain moisture and avoid drying of the soil.. The experiment was conducted in a. growth chamber at a constant temperature of 27 C t 1 C.. The experi-. ment was observed twice a day and as soon as the first seedling emerged, counts were made every 24 hours up to ten days. The treatments were set up in a split-plot design: the oxygen levels were the main plots and the varieties were the subplots. Each treatment had three replications as follows:. Main plot- Oxygen' Concentration %. Subplot - Cotton Varieties. 0% 4% 10% 21%. Delta Pine 16 Delta Pine 61 Stoneville 213 Linea 92 Ll Acala 1517-BR2 Acala 1517-70 San Joaquin 2 T 4852 Pina S-3 Pima S-4. -l-'Non-commercial varieties produced in Columbia and Shafter, respectively. 8.

(21) RESULTS AND DISCUSSION. The effect of three levels of oxygen 0, 4 and 10% on the relative percent emergence and relative days to first emergence on ten varieties of cotton are shown on Table 1.. The 21% oxygen treatment is taken as. 100% emergence and as the time to first emergence. Al1 results are reported at the 99% leve1 of probability. As oxygen was reduced from 21 to lo%, there was no significant change in percent emergence ín al1 varieties.. However, varieties. Stoneville 213, San Joaquin 2 and T-4852 were slightly higher, while Pima S-3 and Pima S-4 were the same, and the remaining varieties were slightly less as to percent emergen&.. Comparing oxygen treat-. ments of 10 and 4%, there was a significant reduction in the percent emergence on alL varieties in the 4% treatment as compared to the 10% treatment.. Variety Delta Pine 16 was significantly higher than. Acala 1517-RR2, Acala 1517-70, San Joaquín 2 and Pima S-3; there were no significant differences among the remaining varieties.. Oxygen. treatments of 0% had a significant reduction ín the percent emergence on varíeties Delta Pine 16, Delta Pine 61, and Linea 92, and no significant difference on the remaining varieties when compared to the 4% treatment.. There was no signifícant difference ín percent. emergence between varieties. Days to Eirst emergence ís very important because poor aeration retards emergence, and the longer the seedling takes to emerge, the more probability there is for an attack by insects, of soil crust and inadequate moísture in the soil. 9. diseases, formation.

(22) 10 With a decrease in oxygen from 21 to lo%, there was no significant increase in relative time to first emergence for al1 varieties.. However,. with a decrease from 10 to 4% oxygen, there was a significant increase in relative time to first emergence for al1 varieties except for Delta Pine 16.. At the 4% oxygen leve1 there was no significant difference. between varieties.. Oxygen treatments of 0% caused a significant. increase in relative time to first emergence for al1 varieties when compared to the oxygen treatment of 4%. significant difference between varieties.. At 0% oxygen there was no In general the decrease. in oxygen decreased percent emergence and increased days to first emergence which is in agreement with many researchers such as Dasberg, et.al. (1966), Hunter and Rich (1925), and Aceves-Navarro (1974). Varietal tolerance to decreases in oxygen cannot be determined in a straightforward way because different varieties show different tolerance at each leve1 of oxygen, and therewas hardly any significant difference between varieties within each oxygen treatment. To determine the most tolerant varieties, an evaluation of the relative percent germination and relative days to first emergence was made at each oxygen level.. The overa11 results were as follows in tolerance. to decreasing low oxygen conditions:. T-4852, Stoneville 213, Delta. Pine 16, Acala 1517-70, San Joaquin 2, Pima S-4, Pima S-3, Acala 1517-BR2,. Linea 92 and Delta Pine 61..

(23) ll. TABLE 1.. Influente of soil oxygen on the relative percent emergence and relative days to first emergence on ten varieties of cotton?. 02 In Flowing Gas 0. 10. 4. Variety. % Ger.. Relative Time. % Germ.. Relative Time. Delta Pine 16. 4.312. 289p. 59. 5awx. 200 stuvw. Stoneville 213. 8.6ay2. 2agp. 37.96xy. 211 stuv. Delta Pine 61. 4.602. 2agp. 32.66~~. 222 rstu. 74.73vw. 167wx. Linea 92. 6.01~. 2agp. 29.93xy. 222 rstu. 93.3av. 144xyz. % Germ.. Relative Time. 95.42v. 156wxy. 101.54v. 144xyz. Acala 1517-BR2. 5.002. 289p. 21.19yz. Acala 1517-70. 9.95yz. 27aPq. 34.44xy. 211 stuv. 95.69v. San Joaquin 2. 9.76~~. 27BPcI. 21.93y. 233 qrst. 103.25~. 1002. 244. nqrs. 97- 62~. .L 6 7vwx. 133xyz. T-4852. 11.93yz. 267pqr. 39.42xy. 200 stuvw. 106.11~. lllyz. Pima S-3. 10.82~~. 267pqr. 24.94y. 233 q r s t. 100.8Sv. I22xy.z. Pima S-4. 8. ogyz. 2agp. 30.22xy. 222 rstu. 100.25~. 122xyz. _ _.__ --.-- _. ._---_-.-.-. -------~___~ ----.----- __----- --- .-.- -. + Each value is a mean of 3 replications. Letters p through z after values indicate statistical population for each determination. Mean values are statistically significant to 1% leve1 only íf they do not have a letter common after values..

(24) CONCLUSION. The reduction of oxygen from 21 to 0% has a significant effect on al1 varieties. As oxygen was decreased there was a significant reduction in the percent emergence in al1,varietie.s.. The only variety to have more than. 50% emergence at the 4% oxygen leve1 was Delta Pine 16. As oxygen was decreased there was a significant increase in the time to first emergence in al1 varieties. time to first emergence at 4% oxygen.. 12. Al1 varieties doubled their.

(25) REFERENCES. 1.. Aceves-Navarro, E. 1974. Wheat responses to different combination of oxygen and salinity levels in the root medium. Ph.D. dissertation. University of California, Riverside. l-115 pp.. 2.. Baver, L. D. and R. B. Farnsworth. in the growth of sugai beets.. 3.. Dasberg, S., H. Enoch and D. HilLel. 1966. Effect of oxygen and carbon dioxide concentration on the germination of range grass. Agron. J. 58:206-209.. 4.. Dasberg, S., H. and K. Mendel. 1971. and aeration on seed germination.. 5.. Gingrich, J. R. and 11. B. Russell. 1956. Effect of soil moisture tension and oxygen concentration on the growth of corn roots. Agron. Jour. 48:517-520.. 6.. Hunter, C. and E. M. Rich. 1925. The effect of artificial aeration on the soil on Impatiens balsamina L. New Phytol. 24:257-271.. 7.. Kaack, K. and K. S. Kristensen. 1967. Emergence and seedling growth related to oxygen content and oxygen diffusion rate in different soils. Agron. Jour. 59:541-544.. 8.. Wanjura, D. F., E. B. Hudspeth, and J. D. Bilbro. 1969. Emergence time, seed quality, and planting depth effects on yields and survival of cotton (Gossypium hirsutum L.). Agron. Jour. 61: 63-65.. 13. 1940. Soil structure effects Soil Sci. Soc. Am. Proc. 5:45-48.. The effect of soil water Jour. Exp. Botany 22:992-998..

(26) Experiment 2: The effect of different combinations of oxygen in the root media on the growth of four cotton varieties (Gossypium hirsutlrm and G. barbadense L.).. LITERATURE REVIEW. Much of the information concerning the importance of soil oxygen to cotton growth is based on inference rather than on quantitative data obtaincd from the field (Patrick, et al., 1973).. Influente on Root Development t Rate and amount of growth.. Roots need a constant inflow of molecular. oxygen from the outside (Vartapetian, 1973) if their normal metabolism and function are to be maintained.. Whatever is the cause of anaero-. biosis, the two essential factors are the gas composition of the medium in the root zone and the actual root resistance to anerobiosis (the ability of the roots to continue growth and assimilate nutrient when the oxygen content is minimal).. The supply of oxygen reaching the. root surface of the plant growing in the soil is largely controlled by i) the rate of gaseous exchange between the air in the soil and the air above the soil, and ii) the condition in the immediate root environment which influente the transfer of the oxygen from the soil pores to the root surface (Wiegand and Lemon, 1958).. The greatest. respiratory activity occurs in the root tip zone with a gradient in respiration with distance along the root (Luxmoore, et a1.1970b). Initial reduction in the rate of cotton tap root extension was obtained 14.

(27) 15 at 2 to 5% levels of oxygen, and the elongation rate was about the same at 10% and 21% oxygen (Stolzy, 1972).. Oxygen concentration below. 10% sharply reduced root penetration and it was necessary to reduce oxygen levels to approximately 5% before root length decreased (Tackett and Pearson, 1964).. Soil oxygen content (Patrick, et al., 1973). controlled the penetration and development of cotton roots in alluvial soils.. An adequate supply of soil oxygen at al1 depths in the root. zone was necessary for effective root development (Patrick and Delauene, 1975).. Even temporary periods of oxygen deficiency cause damage to. root systems and cause heavily fruiting cotton plants to shed bolls and squares which decrease yields. Subsoil oxygen concentrations of 15% or higher are considered to be adequate for good root growth.. The oxygen must also be present. during the first part of the growing season or roots will not develop adequately in the lower depths of the profile.. Even if the oxygen. content of the subsoil increases to a normal leve1 during the last part of the growing season,. few roots will develop at lower depths. (Patrick and Delauene, 1975).. Amount of oxygen and carbon dioxide.. Oxygen concentration gradients. exist between the atmosphere and the cells of plants.. Roots of. plants growing in a field may receive oxygen by diffusion through the soil and root wall (soil aeration) or by diffusion from the atmosphere, via gas spaces that occur between cells within the plant (plant aeration) (Luxmoore, et al., 1970a)..

(28) 16 The root has four levels of activity depending on the concentration of oxygen present (Stolzy, 1972): i) the subsistence leve1 is between 1 and 3% oxygen, below 1% oxygen the root loses weight;. ii) growth. of existing root tips needs oxygen concentration between 5 and 10%; iii) initiation of root growth needs concentration of 12%; and iv) absorption of minerals is done at oxygen levels above 15%. Luxmoore and Stolzy (1972) have indicated three types of oxygen concentration profile within the roots.. The first is a continuous. decrease in oxygen concentration from the top of the root to the tip of the root.. This is associated with conditions that promote high. values of plant aeration.. Plant aeration (larger than 50%) occurs with. roots of larger radii, shorter root length and thicker water films. The second type is formed by three sections:. i) the upper part of. the root has a continuous decrease in oxygen concentration and oxygen diffuses both by soil and plant pathways; .ii) the midsection has very little change in oxygen concentration and soil aeration is essentially the only process of oxygen supply to the root; iii) the lower root section has a decrease in oxygen concentration to the root tip and the oxygen supply from the soil pathway (radial) may be redistributed longitudinally to the root tip.. The third type is where. plant aeration is low (less than 35%). Three sections are also distinguished:. i) the uppermost section is essentially the same as. for the other profile; ii) the midsection indicating a longitudinal redistribution of oxygen flux back to the upper part of the root; iii) the lower section is similar to the second profile.. Soil. aeration supplies al1 respired oxygen in the two lower sections..

(29) 17 Most roots probably grow and respire normally if the oxygen at the root surface is in equilibrium with air containing betwecn 5 and 20X oxygen and the carbon dioxide at the root surface ís in equilibrium with air containing less than 1% carbon dioxide (Woolley, 1965).. Pearson. and Lund (1968) found good growth with cotton plants at an oxygen concentration that varied frorn 1.6 to 18% and with carbon dioxide at 4% at a depth of 75 cm.. The carbon dioxide was nearly twice as much. at the 150 cm depth with the oxygen content at 12 to 13%. Anaya and Stolzy (1972) using Mexican wheat varieties found that root growth was affected principally by oxygen trentments, showing a quadratic effect.. The highest oxygen treatment (21%) caused a. reduction in root growth and the lowest oxygen treatment (0.9%) drastically reduced grain production. at 9.6% oxygen level.. Maximum yields were obtained. Aceves-Navarro (1974) also using Mexican wheat. found that oxygen concentration in the rhizosphere of 0% decreased the number of roots absorbing water, while no significant effect was observed at 12 and 21% oxygen.. Chang and Loomis (1945) using water. culture reported that roots of wheat, maize and rice grow well and function normally with 5 to 10% oxygen and function slowly at 1 to 2% oxygen.. Baver and Farnsworth (1940) in studies on sugar beets. in NW Ohio in soils with poor aeration showed beet produced short, sturdy roots with many auxiliary roots while in well aerated soil produced long tapering beets. Oxygen leve& of 1 to 10% without carbon dioxide reduced the rate 01. cell &ìv‘isìon ìn. br0d. ‘bean as much as 8VZk at the enb of a 24-hour.

(30) 18 treatment; however, after the roots were returned to air, cell division rapidly resumed (Williamson,. 1968).. Nitrogen gas treatment reduced. cell division in secondary roots within 15 minutes, stopped al1 division with 24 hours and frequently killed primary root tips.. hfter being. returned to air, the rate of ce11 division was approximately 70% of normal within 48 hours in the older secondary root system, but few new roots developed. Concentrations of carbon dioxide around the growing root of Lmpatiens balsamina - were probably very high due to the respiration of roots and the activity of soil organisms (Hunter aud Rich, 1925). When CO2 concentrations have reached a certain intensity they could have a narcotic effect on the protoplasm of root hairs which are exposed to its influente.. The functional activity of the root hair. cells, and other cells of the root, may be temporarily suspended until the. carbon dioxide accumulatian has been sufficiently reduced by. natural diffusion.. Increased chlorosis of northern bean frequently. associated with poorly aerated conditions, cannot be attributed primarily to a reduced oxygen leve1 at the roots (Lindsay and Thorne, 1954). Increasing levels of carbon dioxide at the root surface of plants growing in a bicarbonate medium may contribute to chlorotic conditions by raising the bicarbonate level. In water culture with carbon dioxide bubbling through the solution, a concentration of 15 or 20% carbon dioxide may be lethal to whent, maize. and rice plants (Chang and Loomis, 1945).. The toxic effect of. carbon dioxide on plants was due to the change in the interna1 pH of the cells which forms hydrogen-bonded compounds with proteins and changed the composition of the protoplasm..

(31) 19 Harris and Van Ravel (1957) using tobacco plants compared respiratíon rates of plants with 20% oxygen to plants with 15% 02 plus 5% CO2, and found a great reduction in the rate.. They also íound a moderate. reduction with 10% oxygen and 0% carbon dioxide and no reduction with 1.5% oxygen and 0% carbon dioxide.. In studies with mixtures of gases. containing 1 to 10% oxygen, plus enough carbon dioxide to cqual 21%, killed part of the secondary root system but rareLy killed the primary root tip (Williamson,. 1968).. High concentration of carbon dioxide is. more injurious than zero oxygen.. Temperature has a direct influente. Soil temperature. -. plant roots (Taylor and Ashcroft, 1972).. on the growth of. Temperature controls root. growth by varying the minimum oxygen concentration necessary for the ful.1 growth rate.. XE the temperature of the soil were below. 18oC, the oxygen concentration to produce maximum growth could he as low as 2.2%.. Soil moisture. -. At 30°C the maximun growth rate occurs at 21% oxygen.. Following flooding of tomato and tobacco plants, there. is a rapid reduction in transpiration and the water absorbing capacity of the roots (Kramer, 1951). of the shoots.. This is followed by more or less wilting. After 3 or 4 days of the flooding, the lowest leaves. begin to turn yellow and die.. The injury and death of the leaves may. be caused by toxic substances moving up from the dead roots from the surrounding soils.. When the moisture content of soil was increased,. there was a reduction in growth of corn roots (Ltiwton, 1945). He found an increase in growth when air was forced through the soil at high moisture content.. Oxygen concentration of 10.5% or greater had.

(32) 20 a great influente on the response of radicle elongation to soil moisture stress (Gingrich and Russell, 1956).. Wiegand and Lemon (1958) found. that at field capacity the concentration of oxygen at a root surface is suboptimal for normal root respiration in Miller clay but optimum in Amarillo fine sandy loam.. The concentrations of oxygen at the root. surface increased linearly with the logarithm of soil moisture tensions. In Mississippi River alluvial soils the better drained, coarser textured soils had high oxygen content at al1 depths in the profile and better cotton growth than the poorer drained soils which were usually low in oxygen (Patrick, et al., 1973).. Soil compaction.. Gardner and Danielson (1964) indicate, that the factors. governing root penetration in high mechanical impedence zones are aeration, which affects the respiration process, and root moisture content, which acts through its effect on the ce11 turgor and root rigidity. Physical resistance provided by a high bulk bensity soil slowed root penetration of tomatoes, in the presente of a nonlimiting ODR (Rickman, et al., 1966).. Low oxygen diffusion rate values in the. high bulk density soil stopped root growth. Compacted soil layers under normal conditions can develop low or limiting oxygen diffusion rates and reduce the growth of plant roots. The decreased gas transport through the relatiuely thick water films surrounding the roots at low tensions is responsible for the lack of penetrating ability and served to counteract the effect of the high root moisture content.. Decreased aeration also Lowered the. penetrating ability (Gardner and Danielson, 1964). The rate of '.

(33) 21 growth of unimpeded corn roots declines when the oxygen content. falls. below 10% and the growth of impeded roots is seriously reduced under these conditions (Gil1 and Miller, 1956).. Air capacity.. Taylor and Ashcroft (1972) found a 50% loss in crep. density at a soil air porosity of 2%, as compared to a 12 or 16% losc at. 8% porosity.. These effects are not limited to root crops since. similar qualitative results have been found for other kinds of crops.. Variation in species.. Roots of some species nay be more tolerant. to anaerobic conditions than those of other species because they are better supplied with oxygen by diffusion from the shoots through air spaces in stems and roots (Uoolley, 1965). in root tissue are filled with gas.. The intercellular spaces. There is an uninterrupted air. space from the above ground tissue to the region only a few cells from the tip of the root.. Enough oxygen could diffuse down the root. to supply a root even though that root may not receive oxygen from its surrounding environment. The rate of metabolic oxygen uptake by root tissue varies with the genetic background and the physiological age of the tissue (Lemon and Wiegand, 1963).. Because of these factors, differences exist in. intensive and extensive characteristics of plants, such as metabolic pathway and concentration of reaction loci. Luxmoore and coworkers (1970b) found that maize roots have highcr permeability than rice.. They also reported that an increase. in maize. root radius and in water film thickness induced a decrease in oxygen.

(34) 22 concentration in the root, decreased the mean respiration and increased the percent plant aeration.. For rice under flooded conditions, Luxmoore. and coworkers (197Oc) found that an increase in root radius and an increase in water layer thickness is associated with an increase in oxygen concentration within the root, particularly at the root Wall. Percent root porosities of corn, sunflower and Pato wheat were greatly increased when the roots were flooded as compared to non-flooded conditions.. This was not true for barley and tomato.. Tolerance to excess. moisture was related to plant interna1 aeration which was higher due to increased root porosity (Yu, et al., 1969).. By reducing oxygen in. the rooting media from 21% to 1.8%, there was a significantly higher concentration of N, K, Ca, Na, Cl, and B in leaves of oranges than in leaves of lemon, while in the roots of orange there was a significantly lower concentration of Mg, Zn, Mn, and Fe than in lemon roots (Stolzy, et al., 1975).. Rate of - exchange:. When oxygen is plentiful, the substrate supply at. the reaction loci determines the reaction rate (Lemon and Wiegand, 1962).. Chemical processes involved in substrate supply are particu-. larly sensitive to temperature.. When the oxygen concentration at the. root surface is below the critica1 level, diffusion controls the rate of oxygen uptake. temperature.. This physical process is relatively insensitive to. The critica1 oxygen concentration at the root surface. is strongly dependent upon the radius of the root and the diffusion coefficient of oxygen within the root.. Diffusion is the single most. important mechanism in soil aeration (Letey, et al., 1967).. Oxygen.

(35) 23 Oxygen diffuses in response to a gradient from the aerial atmosphere through the gas-filled pore spaces.. Oxygen then dissolves in the. soil solution and diffuses to the respiratory sites.. Carbon dioxide. diffuses in the opposite direction from oxygen.. Modification of roots.. Three or four days after flooding, adventitious. roots begin to develop on tomato and tobacco (Kramer, 1951).. Flooding. probably stops the downward translocation of carbohydrates and auxins and a possible accumulation at the water line is responsible for hypertrophy and development of adventitious roots.. Those plants. which produced adventitious roots suffered the least injury and showed a greater degree of recovery.. Poor aeration of the substrate always. resulted in a significant modification of root structure as compared with roots grown in a well-aerated substrate (Schramm, 1960). Adventitious roots grown on poorly aerated substrate, have larger steles as well as three or four more layers of cells ín the cortex than the normal root. Mitochondria are irreversibly damaged in pumpkin roots after 50 hours of anerobiosis (Vartapetean, 1973). Two main types of lesion were found.. In the first case mitochondria swell and increase con-. siderably in sise.. The outer membrane of the mitochondria moved away. from the inner membrane. Therefore, a Sharp increase occurred in the inner mitochondrial compartment and in the inter-membrane space. The mitochondrial matrix clarified and only a few electron dense granules remained in it.. In the second case there was a strongly.

(36) 24 increased compactness of the mitochondria, their entire inner compartment being filled by compact granules and some vesicles, remnants of destroyed crystae.. Together with the change in mitochondrial. . ultrastructure, oxygen deficiency led to destructive changes of the cellular organelles.. The protoplasm clarified, the number of free. ribosomes decreased sharply, the cisternol of the endoplasmic reticulum swelled, ce11 nuclei decreased in sise and the nuclear envelope was fragmented into small pieces which were vesicles shaped in cross section.. The main part of the nucleus became optically empty at. places and some compact granules appeared. Using Mexican wheat varieties Luxmoore and coworkers (1972) found that at high light intensity there was no effect of aeration on root porosity on Inia and Pato varieties, but a large effect was found with Ciano and Tobari.. At high light intensity root porosity was greater. than at low light intensity for both aeration treatments.. Under low. light conditions, the increase in oxygen supply to roots reduced gas space development markedly.. Under high light intensity there. is a larger supply of carbohydrate for the cells and perhaps a more rapid consumption of oxygen..

(37) 25. Influente- on -Top Crowth A study using Mexican wheat varieties by Aceves-Navarro (1974) showed oxygen concentration in the rhizosphere of 0% decreased plant dry matter production by 50% and inhibited tiller production when Anaya and Stolzy (1972). compared to treatments of 12% and 21% oxygen.. also using Mexican wheat varieties found that the highest yields were obtained with 9.6% oxygen, while a slight decrease was found with 21% oxygen and the lowest yields were obtained at 0.9% oxygen treatment. Response of corn to soil moisture tension was more pronounced when growth occurred at a higher oxygen concentration than in lower oxygen levels (Gingrich and Russell, 1956).. Growth responses as a. function of soil moisture tension were governed by the oxygen concentration of the medium when moisture was not limiting.. The con-. centration of oxygen in a plant's root system regulates the rate of total growth of most crops and the rate of seed production of al1 crops (Hardy and Quevedaux, 1976).. The more oxygen a plant system. has, the greater will be the portion of the plant ending up as seed. The less oxygen a plant has,, the greater will be the proportion of the plant ending up as root, stems and leaves.. Soybean and wheat. grew more with 5% oxygen than 21% oxygen because there is less photorespiration.. The opposite is true for seed formation.. Hunter and Rich (1925) found that aeration of the soil has a beneficial efEect on the growth of Impatients balsamina L. by increasing the rate of growth due to a more regular and rapid stem and root.

(38) 26. elongation.. The rate of transpiration and the intcnsity of respiration. of the shoots are increased hy addition of air to the root system. Increased root activity tended to develop a higher degree of turgor pressure in the living cells of the shoot and influente the rates of transpiration, growth, and respiration of this portion of the plant. Reyes-Manzaneras (1975) working with tomato, sunflower, and jojoba Eound that a decrease in oxygen from 21% to 1.5% in the root media reduced leaf conductance, water potential, osmotic potential and xylem potential significantly.. The largest reduction was in treatments. between 6.5% and 1.5% oxygen.. Jnfluence on Water Uptake. Passive Absorption: __-. Inadequate aeration reduces water absorption,. indirectly by reducing the size of the root system and directly by decreasing the permeability of roots to water (Kramer, 1965). In poorly aerated media water absorption is reduced.because of the increased resistance to movement through roots, rather than Interferente with the driving forte causing the uptake of water. The rate of absorption of water could be due to alteratíon in the permeability of the ce11 membranes caused by changes in the intensity of carbon dioxide concentration in the root hair environment (Hunter and Rich, 1925).. Kramer (1940) working. with tomatoes and sunflower found that high concentration of carbon dioxide reduced the intake of water by decreasing passive absorption which is caused by physical changes in the protoplasm and protoplasmic membranes..

(39) 27 These changes decreased the permeability of the protoplasm and increased the resistance to water movement across the cortex from the epidermis to the xylem. Active Absorption:. In wheat plants Aceves-Navarro (1974), found. oxygen concentrations in the rhizosphere of 0% decreased the amount of water transpired with no significant effect at 12 and 21% oxygen.. Respi-. ration in the plant roots produces energy that pushes water up from the roots.. Active water absorption is dependend on adequate aeration (Taylor. and Ashcroft, 1972).. Influente on Nutrient Uptake. Uptake:. Under poor aeration conditions, salt uptake is reduced because. of the accumulation of salt in the root ce11 vacuoles and because active transport in the xylem tissue requires the expenditure of energy released by aerobic respiration (Kramer, 1965). Water cultures of wheat, maize and rice enriched with carbon dioxide reduced the absorption of five nutrients K > N > P > Ca > Mg > P. sium was excreted from the root of the plant.. Potns-. Nitrogen and P was reduced. as an intermediate, while Ca and Mg was reduced due to less water absorption.. In short term experiments with corn, Hammond et al. (1955), found. that absorption of K by the roots as well as growth is reduced by a low supply of oxygen. Oxygen at 5% in the root zone had Little or no effect on the absorption of K or water by the plant.. Lawton (1945), in studies. with corn in soil found that as soil moisture increased the percentages of K, N, Ca, Mg and P decreased.. The order of reduction differed with.

(40) 28. soil texture. For loam soil the order was: K > P > N > Ca > Mg and for silt soil the order was:. K > N > Ca > Mg > P.. Soil treatments which reduce oxygen from 21% to 1.8% and 0.8% for Citrus sinensis seedlings significantly decreased the concentration of N, P, K, Ca, Mg, Zn, Cu, Mn, B and Fe in the leaves and increased these in the roots (Labanauskas,. et al., 1972).. A reduction of oxygen also. caused a significant increase in concentrations of Na, Cl and N and decrease in,K, Ca and Mg in the stem and a significant lower amount of total P, K, Ca, Mg, Cl, Zn, Cu, Mn, B in the whole plant. By increasing oxygen levels in bicarbonate cultures,. there was an. increase in P, Ca, Mg and K in the leaves, while sodium content decreased (Lindsay. and Thorne, 1954).. Potassium content was highest in the chlorotic. leaves.. Sodium may accumulate in the leaves due to low levels of oxygen. in certain portions of the root zone and/or high bicarbonate levels (Lunt, 1966).. Anaerobiosis ner se does not activate sodium uptake, rather it --. increases the rate of sodium uptake on returning to aerobic conditions (Leggett. and Stolzy,. 1961).. Wallihan et al. (1961) found that oxygen deficit resulted in a significant reduction of plant growth, of chlorophyll and of Fe concentrations in the leaves and stems.. Leaf analysis showed a significant reduction. in concentration-of Fe and Mg resulting from low oxygen or addition of calcium carbonate.. The effect of these two factors are additive and. the size of the root is proportional to the Fe concentration in the root. Under anaerobic respiration nitrate nitrogen is absorbed more readily than nitrogen in ammonium form (Taylor and Ashcroft, 1972).. The oxygen.

(41) 29 in nitrates (MO .) may be used to supply the oxygen needs of plants.. hccumulation:. The accumulation of salts in pLant tissue in concentrations. greater than that in externa1 environment is a common phenomenon (Taylor and Ashcroft, 1972).. The rate of sodium accumulation in the shoots is. increased wth aeration, hut can be stopped by returning the plant to an anaerobic situation or by the use of inhibitors (Leggett and Stolzy, 1961).. Potassium and P accumulation was imnediately suppressed by anaero-. bit conditions and returned only to normal value when oxygen is increased. Accumulations are dependent upon energy derived from respirational activities of plnnts (Taylor and Ashcroft).. Water and Oxygen:. The uptake of nutrients depends on the aeration status. and the water condition of the soil (Taylor and Ashcroft, 1972).. Oxygen. concentration above 10% has no significant influente on the accumulation of rubidium ions hy young corn seedling (Danielson and Russell, 1957). Rubidium uptake decreases rapidly with increase. in soil moisture tension.. The critica1 oxygen leve1 decreases with increasing soil tension and is independent of the osmotic pressure of the culture medium. The rate . of ion diffusion was influenced by the thickness of the moisture films rather than by the moisture stress per se and is responsible for controlling the ion absorption rate..

(42) FlATERIALS AND MXHODS. In order to study the influente of different oxygen levels on the growth and yields of four varieties of cotton, seeds were planted directly in cylinders filled with krilium-treated Yo10 silt loam and sealed. The lid was sealed with paraffin and plastic tape.. The lid had a hole in. the center where the seeds were planted and four boles on the sides for two tensiometers and two watering inlets. The treatments were set up in a randomized complete block design in a factorial arrangement (4 x 4) producing a total of 16 treatments which were replicated three times.. % Oxygen. Varieties. 0 4 10 21. Stoneville 213 Acala 1517-70 T-4852 Pima S-4. The two varieties that gave the best results in the oxygen experiment were T-4852 and Stoneville 213.. The three varieties that gave the best. results in the salinity experiment were Stoneville 213, AcaLa L517-70, and San Joaquin 2.. Since Stoneville 213 had already been selected and. San Joaquin 2 gave similar results as did T-4852 with similar genetic origin, which was also selected,. San Joaquin 2 was omitted.. Pima S-4. was used as the fourth variety. The cylinders (14 cm in diameter and 77 cm high) were packed with 13 kg of krilium-treated Yo10 silt loam to a density of 1.3 g/em?, leaving a space of 2.5 cm for air and irrigation.. 30. The cylinders were placed.

(43) 3 1. in a constant temperature bath 28 C +- loC in the greenhouse.. Two ten-. siometers were installed, one tensiorneter cup at 18 cm and the other at 53. cm. below the soil surface to measure soil water potential.. Soil. water potentials were kept above -0.5 bar. Five seeds were planted in each cylinder.. Five days after ger-. mination three were removed leaving two seedlings and 10 days after .germination one seedling was removed leaving one plant in each cylinder. The different oxygen levels were applied to the cylinders 25 days after germination by an inlet and an. outlet. at the top of each cylinder.. A combination of air and nitrogen gas was used to obtain the adequate percent oxygen needed for each treatment. plastic tubing to four cylinders.. The mixture was passed through. To obtain a good sea1 between the. plant and the lid a mixture of 65% paraffin and 3S% beeswax was used. Seven days after the oxygen levels were applied a 0.1 strength Hoagland solution was used to maintain the soil water potential at -0.1 bar.. The. solution was applied when the tensiometer read -0.5 bar. In order to evaluate the effect of oxygen on growth and yield of cotton different determinations were made on the soil and the plant. Oxygen diffusion rates were measured at two depths, 18 and 53 cm sol1 depth (Letey and Stolzy, 1964).. A.. Physiological Responses: a.. Leaf conductance with a diffusion porometer was uscd to determine a diurna1 pattern fron 4:00 am to 7:30 pm every three hours (45 days oid) and at 50% flowering and 50% bol1 fortning stage (Kanemasu, Thurtell and Tanner, 1969).. b.. Xylem potential at 50% flowering stage and 50% bol1 forming stage was determined by pressure chamber (Kaufman, 1968a, Scholander, 1972)..

(44) 32. B.. c.. Osmotic potential of the leaf was determined bv tIlL> isn-. piestíc thermocouple psychrometer (Hoyer nnd Knipling, 1965). To rupture the ce11 membrances the samples were frozen and before using the leaves were thawed out slowly (Barrs, 1968).. d.. Water use - summation of water applied. Growth a. b. C .. Depth of roots Plant height Leaf surface area. cI.. Dry weight productíon of roots, stems, leaves and cotton seeds.. D.. Plant nutrition - N, P, K, Ca, Mg, Na, B , Zn, Ma, Cu, and Fe (Handy and Labanauskas, 1974)..

(45) RESULTS AND DISCUSSION. Oxygen Diffusion Rate:. The different oxygen treatments and the combina-. tion of air and nitrogen gas needed to obtain them are shown in Table 2. The measured amount of oxygen for each treatment is not significantly different for the predetermined oxygen level. Therefore, to facilitate writing, the treatments will be designated as 0, 4, 10 and 21% oxygen instead of 0, 4.3, 10.4, and 20.5%.. Table 2 also shows when oxygen is. reduced from 21 to 0% there is a significant reduction in the ODR in the -2 -1 soil from 0.39 to 0.04 ug cm min for the shallow depth and from -2 -1 for the deeper depth. Therefore, ODR de0.32 to 0.02 ug cm min creases with depth and the difference is decreased with less oxygen. The results of four oxygen treatments on the two most tolerant varieties of cotton as to poor aeration and high salt at germination will be presented.. Plant Physiology:. In order to determine the time of day when maximum. plant stress occurs a diurna1 pattern of the leaf conductance was made every three hours starting at 4:00 a.m. (before sunup) .and ending at 8:30 p.m. (after sundown).. The measurements were made on the upper. part of the leaf and the lower part of the leaf for two oxygen treatments, 21% and 099, on four varieties of cotton. Table 3 shows the results of these measurements at 45 days after germinating for varieties Stoneville 213, Acala 1517-70, T-4852 and Pima S-4. show high conductance between 1O:OO a.m. and 4:00 p.m.. Al1 varieties In both oxygen. treatments, the four varieties had a significantly higher leaf conduc-. 33.

(46) 34. TABLE 2.. Treatment % oxygen. Combinations of air and nitrogen gas to obtain the desired oxygen treatments and ODR resulting from the treatments in the soil.. Air Nitrogen -----ml/min------. 0 4 10 21. 0.0 22.9 57.1 120.0. Measure. % oxygen. --. ---- -.. 120 97.1 62.9 0.0. ODR ug/cm? min. 53 cF 18 cm. 0 4.3 10.4 20.5. -----. Each value is a mean of three replications.. 0.04 0.26 0.29 0.39. .---.--. 0.02 0.07 0.14 0.32. .----- --.---.

(47) 35. TABLE 3.. Influente of soil oxygen treatment on the diurna1 pattern of leaf conductance on the bottom and top of the leaf of four varieties of cotton determined 45 days after germination?. Uariety. -1 Leaf conductance (cm sec ) on each surface % of soil-02 in flowing gas 0 --~--21 Bottom Bottom Top Top. Time. Stoneville 213. 4:00 7:00 1O:OO 1:00 4:00 7:30. am am am pm pm pm. 0.019 0.090 0.152 0.217 0.262 0.027. 0.017 0.019 0.055 0.051 0.039 0.015. 0.016 0.146 0.606 2.000 1.259 0.017. 0.016 0.038 0.229 0.718 0.397 0.014. Acala 1517-70. 4:00 7:00 10:00 1:00 4:00 7:30. am am am pm pm pm. 0.025 0.072 0.087 0.236 0.187 0.029. 0.018 0.021 0.040 0.055 0.041 0.015. 0.021 0.069 0.185 1.344 0.438 0.016. 0.016 0.023 0.070 0.097 0.223 0.014. T-4852. 4:00 7:00 1O:OO 1:00 4:00 7:30. am am am pm pm pm. 0.023 0.043 0.185 0.653 0.376 0.030. 0.018 0.020 0.030 0.084 0.030 0.015. 0.024 0.082 0.309 0.987 1.529 0.018. 0.017 0.028 0.114 0.262 0.124 0.014. Pima S-4. 4:00 7:00 10:00 1:00 4:00 7:30. am am am pm pm pm. 0.017 0.026 0.129 0.811 0.349 0.022. 0.017 0.018 0.073 0.120 0.077 0.015. 0.016 0.082 1.021 2.000 2.000 0.015. 0.016 0.022 0.151 0.493 0.388 0.014. -----. +. -.~----__I__-__------. Each value is a mean of three replications.. -_--. --_.

(48) 36 tance on the lower part of the leaf than on,the upper part.. A decrease. in oxygen significantly reduced the leaf conductance for al1 varieties on both sides of the leaf. Determinations of leaf conductance, xylem potential and osmotic potential were made 53 and 93 days after germination, and water use was determined at harvest.. The results are shown on Table 4.. In the. first determination, when the plants were 53 days old, the following was found:. i) significant reduction in leaf conductance for al1. varieties, the lowest conductance was with Stoneville 213 and the other three behaved similarly;. ii) no significant changes. in xylem. potential for al1 varieties, except Acala 1517-70 which had a significant increase in the 10 and 0% oxygen treatments, and was significantly lower at 21% oxygen than the rest but significantly higher at 0% oxygen than T-4852 and Pima S-4; in osmotic potential.. iii) no significant differences. These results show that reduction in leaf. conductance (stomatal closure) at low oxygen is due to a physiological effect and not to water stress because there was no significant change in the xylem potential. In the second determination when the plants were 93 days old different results were obtained.. Significant reductions in leaf conduc-. tance were found for varieties Pima S-4 and T-4852.. The largest re-. duction was in oxygen treatments 10 to 4% and from 4 to 0%.. No sig-. nificant changes in leaf conductance was measured for the other two varieties.. The highest conductance was found for Pima S-4 followed. by T-4852 with no significant difference between Acala 1517-70 and Stoneville 213.. Studies with tomato, sunflower and jojoba by Reyes-.

(49) TABLE 4.. Variety. Stoneville 213. Influente of soil oxygen on physiological processes (leaf conductance, xylem potential, osmotic potential and water used) with four varieties of cotton at two stages of growth.+. (2YS). Units. 0. 53. Leaf conductance (cm sec-1) 0.1052 Xylem potential (bars) -11.83~~~ Osmotic potential (bars) -15.02~~~. 93. Leaf conductance (cm sec-l) Xylem potential (bars) Osmotic potential (bars). 140. 0.1052. 50422. Water used (ml). % of soil in flowing gas 4 10 21. 0.422tu -1350wxy -12.882 .097vwxyz. 18615x. .218wxyz .267vwxy -12.25~~ -11.42~~ -16.08wx -13.89xyz .052z -15.OOxyz -24.90t. .077xyz -14.08~~ -18.18vwx. 18308x. 24265~. C.V.. +t-. 16.9 8.6 6.0 16.2 10.1 6.7 5.4. w 4. Acala 1517-70. 53. 93. 140 T-4852. Leaf conductance (cm sec-1) .133yz -9.172 Xylem potential (bars) -15.52~~ Osmotic potential (bars). Leaf conductance (cm sec -1 ) .075vwxyz .180st Xylem potential (bars) -21.5Ow -18.OOwx -16.35~~~ -18.45~~~ Osmotic potential (bars) Water used (ml). 53. .182xyz Leaf conductance (cm sec -9 -12.5Owxy Xylem potential (bars) -15.41xy Osmotic potential (bars). 93. Leaf conductance (cm sec Xylem potential (bars) Osmotic potential (bars). 140. .335uvw -11.42~~ -18.56~. Water used (ml>. -1 ). .342uvw -11.75~~~ -15.ooxyz. .500st -13.5Owxy -16.682. .580rs -18187~ -15.5oxy. 16.9 8.6 6.0. .086wxyz -13.67~~ -17.48~~~~. .124tuvwx -14.33xyz -17.20~~~. 16.2 10.1 6 .. 35117uv. 32400~. 5.4. .305uvwx -12.33wxy -18.01~~. .706r -12.5Owxy -13.65~~. 16.9 8.6 6.0. .186s -12.38~~ -17.2Owxy. 16.2 10.1 6.7. .09lwxyz .140stuvw .150stuv -18.OOwx -12.58~2 -12.75~~ -21.03~ -17.63~~~~ -16.2Owxy 6517~~. 20780x. 25725~. 34992uv. 5.4. 7.

(50) TABLE 4.. Variety. Pima S-4. (continued) Age (days). Units. 0. % of soil in flowing gas 4 10 21. 53. Leaf conductance (cm sec') .321uvwx Xylem potential (bars) -14.38wx Osmotic potential (bars) -15.55xy. .224wxyz -15.13w -13.78~~~. .406tuv -13.42~~~ -12.942. .640rs -13.oOwxy -15.3oxy. 93. Leaf conductance (cm seCl) .118uvwxy Xylem potential (bars) -13.58~~ Osmotic potential (bars) -12.952. .172stu -1l.OOz -16.08~~~. .320r -11.502 -15.26~~~. .352r -14.ooyz -15.09yz. 25618~. 37265~. 35952u. 140. Water used (ml). 8933y. C.V. *. 16.9 8.6 6.0 16.2 10.1 6.7 5.4 W. +Each value is a mean of three replications. Letters s through z after values indicate statistical population for each determination. Mean values are statistically significant at 1% leve1 if they do not have a letter in common after values. *c.v. = coefficient of variability expressed in percent.. 03.

(51) 39. Manzanares (1975), also showed a decrease in leaf conductance due to decrease in oxygen. Significant effects on xylem potentials were found for al1 varieties, except Pima S-4, which had a significantly higher value than the rest at 0% oxygen treatments, while Stoneville 213 had a significantly higher value at 0% oxygen.. Stoneville 213 and T-4852. had a significant decrease in xylem potentials as oxygen was decreased from 4 to 0% and Acala 1517-70 had a similar effect in the 10 to 0% oxygen treatment.. Similar results were found by Reyes-. Manzanares (1975) working with tomato, sunflower and jojoba. Variety Acala 1517-70 had no significant differences on osmotic potential, but significant effects were found for the other varieties. At 0% oxygen treatment, Pima S-4 had a significantly higher osmotic potential than Acala 1517-70 and Stoneville 213. also higher than T-4852.. Stoneville 213 was. In treatments 4%, lo%, and 21% there was no. significant difference between Acala 1517-70, T-4852, and Pima S-4, while Stoneville 213 had a significant decrease from 21% to 10% oxygen and a significant increase from 10% to 4%.. Reyes-Manzanares (1975). also found a reduction in osmotic potential as oxygen was decreased in the root zone of tomato, sunflower and jojoba. The above results show that the Pima S-4 has higher leaf conductance, xylem potential and osmotic potential than the other three varieties which is also correlated to higher yields, especially to higher leaf conductance.. Soil water stress was not low enough to cause. low leaf conductance, especially at high oxygen levels.. The reduction.

(52) 40. in leaf conductance and xylem potential in Stoneville 213, Acala 1517-70, and T-4852 is probably due to the aging phenomena (senescente).. These. varieties have a shorter life cycle than Pima S-4 and reduced photosynthesis occurs in them, while Pima S-4 has a longer period of time to produce and accumulate photosynthates as cotton bolls are filled.. When. plants get older from 53 days to 93 days, there is a significant reduction in leaf conductance in al1 varieties, especially at lower oxygen levels.. This is also true for xylem potential and osmotic potential. which could be caused by decrease in photosynthesis and senescente as the plant matures and enters dormancy. Water uptake was determined by adding up al1 the amounts of water applied to each plant (Table 4).. There was a significant effect on water. use for al1 varieties due to reduction of oxygen. Stoneville 213 and T-4852 had a significant reduction in water uptake as oxygen was reduced from 21% to 0% and especially more so below 4% oxygen. and Pima' S-4. Acala 1517-70. had a nonsignificant increase as oxygen was reduced from. 21% to 10% and a significant decrease as oxygen was reduced from 10% to 4% and especially at 0%.. In the 21% oxygen treatment there was no. significant difference in water use between Pima S-4 and T-4852 and a nonsignificant difference between Acala 1517-70 and Stoneville 213. In the 10% treatment, Pima S-4 and Acala 1517-70 were significantly higher than T-4852 and water use by T-4852 was higher than Stoneville 213. In the 4% treatment, Pima S-4 and Acala 1517-70 were significantly higher than T-4852 and Stoneville 213.. Oxygen treatment of 0% showed Pima S-4. was significantly higher than Stoneville 213. Working with wheat,.

(53) 41. Aceves-Navarro (1974) found a reduction in water transpired with decrease in oxygen.. Water uptake shows a better correlation with. leaf conductance with al1 varieties when determined at an earlier stage (53 days) than with conductance determined at a latter stage (93 days) because of maturity.. Pima S-4, due to the longer growth. period, was the only variety to show good correlations in measured values at the latter date.. Based on partial water uptake the best. age to determine Leaf conductance is between 3 to 5 weeks, especially for plants with low oxygen in the rooting medía.. Root Growth: ___-. A reduction in oxygen in the rooting media had a signi-. ficant effect yn the depth of root for ali varieties (Table 5). As oxygen is reduced from 21% to 0% the roots do not grow as deep in soil. Acala 1517-70 and Stoneville 213 are the most affected, followed by T-4852, with Pima S-4 being the least affected.. The most significant. difference among varieties was found in the 0% oxygen treatment. There was no significant difference between Acala 1517-70 and Stoneville 213 which were significantly shallower than Pima S-4 and T-4852. two were not significantly different.. The latter. Stolzy (1972) reported a reduc-. tion in tap root length between 2 and 5% oxygen which coincides with these results which showed the most significant reduction occurred below 4% oxygen.. Tackett and Pearson (1964) report that oxygen content. below 10% oxygen reduces root penetration and below 5% decreases root length. A decrease in oxygen also significantly reduced the dry weight of roots for al1 varieties (Table 5).. Varieties T-4852, Acala 1517-70,.

(54) TABLE 5.. Variety. Influente of soil oxygen on plant growth (root, st:m and leaf) and yields (seed cotton) for four varieties of cotton.. Part. Units. 0. % of soil in flowing gas 4 21 10. --. C.V.. Stoneville 213 Root. 1.002 16.0~~ 5.27~~ 46.0~ 3.932 732.41~ 10.202 o.ooz. 1.7oxyz 34.ouv 8.53~~ 86.Ovw 13.lOxy 2191.32xy 23.33~~ 3.75xy. 3.13w 2.07wxyz 4.40t 43.7t 9.53wx 9.27wxy 8.53~~~ 76.7~~~ 13.60~~ 17.27~~ 2224.11~~ 2613.54~~~ 24.93~~ 29.93wx 11.80~ 6.00~~~. 14.5 9.9 15.1 7.9 16.9 14.0 14.4 12.9. Acala 1517-70. Root. 0.87~ 13.32 3.332 4.902 4.032 629.762 8.23~ 0.302. 2.93wx 33.3uv 12.33~~~ 84.7~~~ 21.77~~ 3149.66w 37.03vw 5.oOwxy. 4.47v 43. Ot 17.53u 85.0~~~ 29.1ou 3963.50x 51.1ou 8.03~. 5.7ouv 47. Ot 14.03uvw 77.3wxy 24.77~~ 3191.6Ow 44.5ouv 7.5ov. 14.5 9.9 15.1 7.9 16.9 14.0 14.4 12.9. Root. 1.53yz 22.7~~ 5.57yz 43.72 4.702 776.71~ ll.802 0.372. 6.13~ 2.67wxyz 41.0tu 40.7tu 12.4Ovwx 10.07wxy 65.7~ 65.3~ 24.83~~ 15.00x 3269.16vw 1932.44y 43.37uv 27.73~~~ 3.ooy 4.53wxy. 7.43t 55.7s 16.77~~ 72.3~~~ '25.93~~ 3005.68~ 50.13u 6.08vw. 14.5 9.9 15.1 7.9 16.9 14.0 14.4 12.9. Dry weight (gr) Depth (cm) Stem Dry weight (gr) Height (cm) Leaf Dry weight (gr) Area (cm) Total Dry weight (gr) Seed cotton Dry weight (gr). T-4852. Dry weight (gr) Depth (cm) Stem Dry weight (gr) Height (cm) Leaf Dry weight (gr) Area (cm) Total Dry weight (gr) Seed cotton Dry weight (gr) Dry weight (gr) Depth (cm) Stem Dry weight (gr) Height (cm) Leaf Dry weight (gr) Area (cm) Total Dry weight (gr) Seed cotton Dry weight (gr). c N.

(55) TABLE 5.. Variety. (continued). Part. Units. % of soil in flowing gas- 4 10 21. 0. C.V.. -. Pima S-4. Root. Dry weight (gr) Depth (cm) Stem Dry weight (gr) Height (cm) Leaf Dry weight (gr) Area (cm) Total Dry weight (gr) Seed cotton Dry weight (gr). 1.37yz 24.7~~ 9.33wxy 70.3xy 7.17yz 1191.08z 17.81~~ 5*03wxy. 6.10~ 31.3vw 17.80~ 97.7uv 12.63~~ 1991.66y 36.53~~ 14.27t. -. 7.83t 42.0tu 25.27t 103.7u 17.67~~ 2796.52wx 50.77u 21.50r. 7.77t 42. Otu 25.97t 103.7u 17.93wx 2696.7Owxy 51.67~ 17.90s. +Each value is a mean of three replications. Letters s through z aftervalues indicate statistical population for each determination. Mean values are statistically significant at 1% leve1 if they do not have a letter in common after values.. 14.5 9.9 15.1 7.9 16.9 14.0 14.4 12.9 c w.

(56) 44. and Stoneville 213 had a significant reduction below 21% oxygen while the reduction in Pima S-4 occurred below 10% oxygen.. Root dry weights. of Pima S-4 and T-4852 were significantly higher than Acala 1517-70, and Acala 1517-70 was significantly higher than Stoneville 213 in the 21% oxygen treatment.. At 10% oxygen Pima S-4 was significantly higher. than T-4852, and T-4852 was higher than Acala 1517-70 and Stoneville 213. In the 4% oxygen treatment Pima S-4 was significantly higher than Acala 1517-70, T-4852 and Stoneville 213, while Acala 1517-70 was higher than Stoneville 213.. In the 0% oxygen treatment there was no. significant difference within varieties.. Stems:. Reduced oxygen had a significant effect on the height of the. stem at only 0% (Table 5).. Pima S-4 was significantly higher than. Acala 1517-70, Stoneville 213 and T-4852.. In the other oxygen. treatments, Pima S-4 was significantly higher than Acala 1517-70 and Stoneville 213.. The latter one was significantly higher than T-4852 at. 10% and 4% oxygen.. Reyes-Manzanares (1975) found the same result at. 1.5% oxygen instead of 0% for.tomato, sunflower and jojoba. A reduction in oxygen also had a significant effect on al1 varieties as to stem dry weight (Table 5).. Stoneville 213 had no signi-. ficant reduction at the 4% leve1 and T-4852 at the 10% level. Acala 1517-70 had a significant increase at the 10% leve1 and had a significant decrease at the 4% level.. Pima S-4 was significantly heavier. than al1 varieties in al1 oxygen treatments.. Dry weight of stem of. T-4852 and Acala 1517-70 were significantly higher than Stoneville 213.

(57) 45. in the 21% treatment, while at 10% oxygen Acala 1517-70 was significantly higher than T-4852 and Stoneville 213. In the 4% oxygen treatment, there was no significant difference between Acala 1517-70 and T-4852 and no significant difference between T-4852 and Stoneville 213. At 0% oxygen there was no significant difference between the four varieties.. Aceves-Navarro (1974) found the most significant reduction. at 0% oxygen for wheat while Reyes-Manzanares (1975) found it to be at 1.5% oxygen for tomato, sunflower and jojoba.. Leaves:. Oxygen reduction had a significant effect on leaf area with. al1 varieties (Table 5).. As oxygen is reduced from 21% to 10% there. is a significant increase in leaf area for Acala 1517-70, a nonsignificant increase for varieties T-4852 and Pima S-4 and a nonsignificant increase for Stoneville 213.. As oxygen is reduced from 10% to 4%, there. is a significant reduction in leaf area for al1 varieties except Stoneville 213.. In the 0% oxygen treatment, there is a significant. decrease in leaf area for al1 varieties.. The 21% oxygen treatment had. no significant difference between varieties, and in the 10% treatment there was no significant difference between Acala 1517-70 and T-4852, no significant difference between T-4852 and Pima S-4 and no significant difference between Pima S-4 and Stoneville 213.. In the 4% oxygen treat-. ment Acala 1517-70 is significantly higher than Stoneville 213, Pima S-4 and T-4852, and at 0% oxygen there is no significant difference between varieties.. Reyes-Manzanares (1975) also found a significant reduction. in leaf area for sunflower and jojoba but the oxygen leve1 was between 12 and 6.5% and the highest reduction at 1.5%.. By reducing oxygen.