Territorio, desarrollo y sostenibilidad ambiental

Method

Cytokinins at the following concentrations were incorporated in the nutrient medium : -

BA : 0, 0.1, 0.5, 1.0, 2.5, 5.0 or 10.0 mg 1"’ 2iP : 0, 5.0, 10.0, 15.0 or 20.0 mg 1"' .

The species listed below were tested.

Rosaceae:- Chaenomeles japonica, Cotoneaster dammeri, Crataegus brachyacantha, Crataegus

’Toba’, Potentilla 'Coronation Triumph', Potentilla 'Sutter's Gold', Prunus cerasifera, Prunus

tomentosa, Pyracantha coccinea. Spiraea

'Froebelii'.

Ericaceae:- Arctostaphylos media, Arctostaphylos uva-ursi. Erica carnea, Gaultheria hlspidula. .Kalmia angustifolia (pink form), Rhododendron

'Chinsayii', R. dauricum, R. fastigiatum, JL* forrestii, R . keiskei, R . leucaspis,

R. lutescens, R. 'P.J.M. Victor’, R.

racemosum, R. 'Vuyk's rosy red’, R.

willlamsianum, Vaccinium vitis-idaea.

Cultures were incubated in light (16 hour photoperiod). Shoot number and length were recorded at the end of a four week incubation period. A four week period was chosen because preliminary experiments showed that most shoots were formed within four weeks and were long enough at the end of the four week period to record with the naked eye. Shoot length was recorded in 5 mm increments thus:-1-5, 6-10, 11-15, 16-20, 21-25, 26-30, 31-35 mm.

Results

The addition of BA to the medium at all concentrations tested resulted in death of explants of Gaultheria hispidula, Rhododendron 'chinsayii' and Rhododendron dauricum. BA concentrations greater than 0.1 mg 1“' resulted in death of explants of Erica carnea, R. fastigiatum and R_. P.J.M. Victor. No toxic effects due to 2 iP were observed.

Shoot number

number plotted against BA concentration. Statistics of fit are included with each figure. Equations for curves are of the form : -

y=b +b, loggX ib^^ logg x^+bj log^x^ ib^logfX^ The probability of non-fit is

<.001 for every Rosaceous plant model <.001 for Arctostaphylos

<.05 for Kalmia

<.001 to N.S. for Rhododendron <.001 for Vaccinium.

Figures 25 to 54 show fitted polynomials for shoot number plotted against 2IP concentration. Equations are of the form : -

y=b +bj X ib^x^+bj x^ ■fb^x'^

i.e. quartic equations. The probability is <.001 for every model,

These models were used to determine optimal shoot numbers and optimal cytokinin concentrations. These are detailed in Tables 2 to 5. In Rosaceae, the optimal concentration of BA for maximal shoot formation ranged from 0.4 to 2.3 mg i^whereas in Ericaceae, the optimal BA concentration ranged between 0.5 and 6.2 rag 1 * . Optimal concentration of 2ip was higher (4.3 to 17.2 mg 1“* in Rosaceae; 10.3 to 20.0 mg 1"' in

Ericaceae). Maximal calculated shoot number on medium containing BA was 5.34 to 26,40 in Rosaceae and 0.61 to 16.49 in Ericaceae; and on medium containing 2ip was 4.02 to 31,27 for Rosaceae and 2.13 to 11.78 in Ericaceae. These can be summarized as follows.

mean shoot no. mean cone.

BA Rosaceae 14.54 1.22

BA Ericaceae 2.76 2.96

2iP Rosaceae 10.25 12.53

2iP Ericaceae 5.27 15.03

The form of the curves was different for BA and for 2iP - different equations were necessary for plotting of the data. The spread of effective concentrations for shoot formation was great for all species for 2iP and for most species for BA. A few species, both Potentilla cultivars. Spiraea and Vaccinium, had a marked peak with a narrow concentration range.

An analysis of variance was conducted to show the main significant effects. These are detailed in Tables 6 to 9. This analysis showed that for both BA and 2iP, concentration had a significant effect on shoot number

(p<.001), species and cultivar had a significant effect (p<.001) and that there was a significant interaction between concentration and species (p<.001).

Mean shoot number for BA was compared with mean shoot number for 2iP and was found to be significantly

different for both Ericaceae and Rosaceae

(p<.001)(Tables 10 and 11). In Rosaceae, BA gave consistently more shoots than 2iP, while in Ericaceae, 2iP gave consistently more shoots than BA.

Shoot length

An obvious decrease in shoot length was recorded with increasing BA concentration (Figures 55 to 81). However, change in shoot length with change in 2iP concentration approximated a normal distribution

(Figures 82 to 117).

A comparison of shoot length between BA treatments with the maximal number of shoots and 2iP treatments with the maximal number of shoots demonstrated that shoot length was significantly greater in 2iP treatments than in BA treatments in all species tested (p<.001) (Tables 12 and 13).

Explant growth

A linear correlation between BA and 2iP

(Tables 14 to 17). Expiant length decreased with increasing cytokinin concentration.

A comparison was made between explant growth on BA medium and explant growth on 2iP medium at the concentrations which produced most shoots (Tables 18 and 19). Explants grew significantly more on 2iP medium than on BA medium (p<.001) in all species.

Origin of shoots

New shoots formed were either axillary in origin or adventitious (derived from a part of the stem other than the leaf axils). Adventitious shoots were formed directly from the stem (not from basal callus). Species which formed adventitious shoots also produced axillary shoots. Types of shoots produced for each species are given in Tables 20 and 21. Species of Rosaceae formed both adventitious and axillary shoots on medium containing BA but only four cultivars formed adventitious shoots on 2iP medium. All Ericaceous species (with 3 exceptions) formed axillary shoots only on both BA and 2iP media.

Figures 1 to 24,

Shoot number after a four week incubation period on medium containing BA.

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