The Correlation between Physiological and Structural Alterations Induced by Copper and Cadmium Stress in Broad Beans (Vicia faba L.)
AbstractPhysiological and structural alterations in broad beans (Vicia faba cv. Giza Blanka) in response to 10-5 M CuSO4, 10-6 M CdSO4 and a mixture of both solutions were recorded in 15- and 25-
day-old plants. These treatments caused significant reductions in shoot height, leaflet area, fresh and dry weights, stomatal frequency, cell area in abaxial epidermis of leaflets, length and width of stomatal guard cells, size of parenchyma in all seedling organs, diameter of metaxylem
vessels, concentration of photosynthetic pigments (Chl-a, chl-b, carotenoids), photosynthetic activity, activities of antioxidant enzymes (CAT, POX, SOD), as well as a major re-shuffle of the protein patterns. Treatments causing reductions in these parameters were mostly in the
order: Cu+Cd > Cu > Cd. The disappearance of a 25-kDa polypeptide by all heavy metal treatments seems to suggest that they reduce cell enlargement and/or the synthesis of the heavymetal- binding phytochelatins (PCs) through inactivation of á-expansin and/or a phytochelatin synthase (each with MM 25 kDa), respectively. The outcome of reductions in stomatal frequency, size, leaflet area, efficiency of narrower xylem vessels, and photosynthetic pigments
is a significant decrease in photosynthetic activity and, consequently, the observed reductions in growth criteria.