Effect of Zn, Cd and Cr on growth, water status and chlorophyll content of barley plants (<i>H. vulgare L.</i>)

To evaluate the potential of barley for the phytoremediation of soils contaminated by metals, we conducted a growth chamber experiment with plants exposed to various concentrations of Zn, Cd and Cr. Growth parameters, chlorophyll content and chlorophyll fluorescence were measured at 15 and 29 days after treatment application, and the metal concentration in the aerial part of the plant, the root and the soil was also measured. In all cases, the amount of metal accumulated in the plant increased by increasing the concentration of the applied metal, and the roots accumulated more metal than did the aerial part of the plant. The amount of Cr found in the soil was significantly lower than that of Cd and Zn. The toxic effect of Zn and Cd on the plant was low, affecting growth only at the highest concentrations. For Zn and Cd at the concentrations used, the decrease in water content was 14% compared with the control and 26% for Cr. For plants treated with the highest metal concentrations, the most significant differences were found in chlorophyll content, which had the lowest values compared with the control (23% for Zn, and 42% for Cd and Cr), and in chlorophyll fluorescence (2% for Zn, 23% for Cd and 29% for Cr). These decreases occurred 29 days after applying the Zn and Cd treatments. In plants treated with Cr, the decrease occurred 15 days after treatment application. Under our experimental conditions, barley is more tolerant to Zn and Cd than to Cr.

Response of coleoptiles to water deficit: growth, turgor maintenance and osmotic adjustment in barley plants (Hordeum vulgare L.)

Cereal crop improvement programmes involve the analysis of a great number of lines every year;the availability of a simple, rapid method that would allow the identification of a trait in the early stages of plant development would facilitate the selection process. This work reports two experiments involving the germination of seeds in Petri dishes, performed to study the effect of water deficit on the growth of barley coleoptiles. In one experiment water stress was induced by allowing evaporation from the Petri dishes;in the other water stress was achieved by adding polyethylene glycol 6000. The growth of the control coleoptiles was greater than that of the treatment coleoptiles in all cases, but with differences between the different genotypes. A significant correlation (P < 0.01) was found between the relative growth of the coleoptiles and turgor maintenance in the seedlings. Significant correlations were also seen between the relative growth of the coleop-tiles and the osmotic adjustment of the flag leaf (P < 0.05) and the grain weight (P < 0.01) in adult plants. The genotypes that showed the greatest relative growth also showed the greatest capacity for osmotic adjustment in the flag leaf and produced the greatest yields in experiments with adult plants. The results indicate that the growth of coleoptiles subjected to water deficit could be used as a selection criterion in breeding programmes designed to improve the tolerance of barley to drought.