1.2 Content of Cd, Cu, Pb and Zn in aerial plant biomass (cultivation in experimental pots)

Experimental plants of the first group (A-I, B-I and C-I) and the second one (A-II, B-II and C-II) treated with BRs in the plant growth stage 29-31 DC did not differ in the growth stage 47 — 49 DC from untreated control and the plants of the third group (not treated in the stage 29 — 31 DC). The first differences in the content of investigated metals were shown in the plant growth stage 73 — 75 DC (Table 5). A distinct trend in copper content was not observed in the plant biomass. Content of lead decreased in all variants of treated plants. A decreased lead content was determined in the plants of the second group (as a whole treated two times) and the third (A-III, B-III and C-III) group (as a whole treated ones), in which the last BRs application was performed in growth stage 59-60 DC. In the first group that was treatedonly once in the stage 29-31 DC, lead content was higher than those in the other two groups. Similarly to lead content in the plants of the second group and the third group, lower cadmium and zinc contents were determined as related to the contents of the first group and in control plants (with the exception of plants treated with 4154 in the third group, where the lower Zn content was not determined). After the harvest of plants in the growth stage 90-92 DC (Table 5), a lower copper content in the first group and the third group (with the exception of plants treated with 4154 in the third group) was determined in plant straw. Likewise in the growth stage 73-75 DC, lower zinc content was determined in all plants of the second group and in the plants of the third group treated with 24-epiBL and 24-epiCS.

growth stage 47-49 growth stage 73-75growth stage 90-92 DC DC DC

(plants) (plants) (straw)

growth stage 47-49 DCgrowth stage 73-75 DCgrowth stage 90-92 DC (plants) (plants) (straw)

Fig. 3. Content of zinc in aerial biomass of plants (mg kg-1 DM)

No significant difference of the cadmium content in the growth stage 90-92 DC was found, with the exception of plants treated with 4154 in the first group and 24-epiBL in the second group. Lower lead content was determined in the plants of the second group and the third group treated with 24-epiBL and 24-epiCS. Copper content was affected more likely
according to the actual and individual status of plants, however, in some cases these physiological processes could be affected by brassinosteroids treatment (Fig. 2). Zinc content in aerial biomass decreased during plant growth (Fig. 3). A significant decrease of cadmium content was determined after the applications of brassinosteroids in the growth stage 73-75 DC in the plants of the second group and the third group (Fig. 4). Lead was accumulated in the plant biomass of the control group during the all vegetation period (Fig. 5). Lower lead

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growth stage 47-49 DC growth stage 73-75 DC growth stage 90-92 DC

(plants) (plants) (straw)

growth stage 47-49 DC growth stage 73-75 DC growth stage 90-92 DC (plants) (plants) (straw)

Fig. 5. Content of lead in aerial biomass of plants (mg kg-1 DM)

content in the stage 90-92 DC was found only in the plants of the second group and the third group that were treated with 24-epiBL and 24-epiCS. No significant difference was found in the plants of the first group that were treated in the growth stage 29-31 DC and in the treatment with brassinosteroid 4154.

1.3 Content of Cd, Cu, Pb and Zn in grains (cultivation in experimental pots)

After the application of BRs, lead content in grains decreased in the second and the third group (Table 5). While copper content significantly decreased in the plants of the third group following 24-epiCS treatment, the decrease of copper content was not statistically significant in other variants. Effect of brassinosteroids on the content of metals in grains of control plants is shown in Fig. 6.