DISEÑO DE ANCLAJES PROYECTO

Macro- and micronutrient contents in roots and shoots of lettuce and garden cress are presented in Fig 5.3 and Fig 5.4a to 5.4d, where Fig 5.3 shows the results of N and Mg analysis and the results for other nutrients are presented in Fig 5.4a to 5.4d. Nitrogen concentrations in lettuce shoot (Fig 5.3a) in plants treated with 0.25 mg L-1 were 50% lower than that in control plants; on the other hand, N concentration did not vary with BAC treatment in lettuce roots (Fig 5.3b) or either tissue of garden cress (Fig 5.3e and 5.3f). Magnesium concentrations in lettuce shoot and root decline in BAC-treated plants (Fig 5.3c and 5.3d) compared to control plants, and was unaffected by BAC treatment in garden cress (Fig 5.3g and 5.3h). Other than N and Mg, no evidence of possible deficiency was observed for any other nutrients (Fig 5.4a to 5.4d). Conversely, the concentrations of several other nutrients increased in response to 0.025 and/or 0.25 mg L-1 BACs. For example, in lettuce shoot, Mo concentration increased, by about 50% at both concentrations of BACs (Fig 5.4a); however, in lettuce root, significant increase was observed for Fe 50%;, P 30%; K 40%; Zn 50% at 0.25 mg L–1 of BACs (Fig 5.4b). On the other hand, no significant increase was found for garden cress shoot for any of the macro or micro nutrient content (Fig 5.4c) but in garden cress root, Cu, Fe, Mo, P, K, and S increased significantly at 0.25 mg L–1 of BACs (Fig 5.4d). However, most of the concentrations were not high enough to suspect BAC-induced nutrient toxicity. The only exception might be Fe, which increased by 50% in roots of both species in response to BACs (Fig 5.4b and 5.4d). Excess Fe can cause oxidative stress in plant tissue (Kampfenkel et al., 1995), which might be an indirect indication of BAC toxicity. The slight increases in uptake of many elements might be due to the dispersing property of surfactants, as one of their inherent characteristics. Enhanced accumulation of certain elements was also observed in response to non-ionic and anionic surfactants in some studies. For example, Cu uptake was enhanced in the root of Halimione portulacoides (Almeida et al., 2009). In another study, natural (tea saponin) and anionic surfactants enhanced the uptake of polychlorinated biphenyls and Cd in corn (Zea mays L.) and sugarcane (Saccharum officinarum L.), respectively (Xia et al., 2009).

Fig 5.3 N and Mg content of lettuce and garden cress exposed to BDDA and/or BDTA. Plants were grown hydroponically for 12 d with 0, 0.025 or 0.25 mg L–1 BACs, individually and in mixture. N content of lettuce and garden cress in shoots (a, e) and roots (b, f); Mg content of lettuce and garden cress in shoots (c, g) and roots (d, h) are shown. Error bars are standard error of the mean (n=3). Within each panel different lower case letters indicate significant differences in N or Mg content (two-way ANOVA and post hoc Tukey tests; p <0.05). Absence of any lower case letters indicates no significant difference among the treatment conditions.

Fig 5.4a Four macronutrients (phosphorus, P; potassium, K; calcium, Ca; and sulfur, S) and 6 micronutrients (boron, B; manganese, Mn; iron, Fe; zinc, Zn; molybdenum, Mo; and copper, Cu) were presented in lettuce shoot exposed to BDDA and/or BDTA. Plants were grown hydroponically for 12 d and treated with 0, 0.025 or 0.25 mg L–1 BACs, individually and in mixture. Error bars are standard error of the mean (n=3). Within each panel different lower case letters indicate significant differences in nutrient content (two-way ANOVA and post hoc Tukey tests; p <0.05). Absence of any lower case letters indicates no significant difference among the treatment conditions.

Fig 5.4b Four macronutrients (phosphorus, P; potassium, K; calcium, Ca; and sulfur, S) and 6 micronutrients (boron, B; manganese, Mn; iron, Fe; zinc, Zn; molybdenum, Mo; and copper, Cu) were presented in lettuce root exposed to BDDA and/or BDTA. Plants were grown hydroponically for 12 d and treated with 0, 0.025 or 0.25 mg L–1 BACs, individually and in mixture. Error bars are standard error of the mean (n=3). Within each panel different lower case letters indicate significant differences in nutrient content (two-way ANOVA and post hoc Tukey tests; p <0.05). Absence of any lower case letters indicates no significant difference among the treatment conditions.

Fig 5.4c Four macronutrients (phosphorus, P; potassium, K; calcium, Ca; and sulfur, S) and 6 micronutrients (boron, B; manganese, Mn; iron, Fe; zinc, Zn; molybdenum, Mo; and copper, Cu) were presented in garden cress shoot exposed to BDDA and/or BDTA. Plants were grown hydroponically for 12 d and treated with 0, 0.025 or 0.25 mg L–1 BACs, individually and in mixture. Error bars are standard error of the mean (n=3). Within each panel different lower case letters indicate significant differences in nutrient content (two-way ANOVA and post hoc Tukey tests; p <0.05). Absence of any lower case letters indicates no significant difference among the treatment conditions.

Fig 5.4d Four macronutrients (phosphorus, P; potassium, K; calcium, Ca; and sulfur, S) and 6 micronutrients (boron, B; manganese, Mn; iron, Fe; zinc, Zn; molybdenum, Mo; and copper, Cu) were presented in garden cress root exposed to BDDA and/or BDTA. Plants were grown hydroponically for 12 d and treated with 0, 0.025 or 0.25 mg L–1 BACs, individually and in mixture. Error bars are standard error of the mean (n=3). Within each panel different lower case letters indicate significant differences in nutrient content (two-way ANOVA and post hoc Tukey tests; p <0.05). Absence of any lower case letters indicates no significant difference among the treatment conditions.

A number of the visible symptoms of stress observed in BAC-treated lettuce were chlorotic and necrotic older leaves and wilted shoots, which may have been due to N and Mg deficiencies (Salisbury and Ross, 1985). However, similar physical symptoms of stress were seen for BAC-treated garden cress as well, although it had N and Mg concentrations similar to those in control plants. Further work is required to ascertain the mechanisms of BACs induced toxicity and any relationship with the changes in nutrient uptake with the plant stress.