Kinetin supplementation modifies chromium (VI) induced alterations in growth and ammonium assimilation in pea seedlings.

In the present study, impact of kinetin (KN; 10 and 100 µM) supplementation on growth, ammonium (NH(4)(+)) assimilation and antioxidant system in pea under hexavalent chromium toxicity (Cr VI; 50, 100 and 250 µM) was investigated. Chromium decreased growth, protein, and nitrogen, and activity of glutamine synthetase (GS) and glutamate synthase (GOGAT) while it increased NH(4)(+) content and activity of glutamate dehydrogenase (GDH). Kinetin at 100 µM decreased growth and NH(4)(+) assimilation, and together with Cr, it increased Cr toxicity. Chromium and 100 µM KN increased superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities while decreasing activities of catalase (CAT), glutathione reductase (GR) and dehydroascorbate reductase (DHAR). Ascorbate and glutathione levels were decreased by Cr and 100 µM KN. In contrast, supplementation of 10 µM KN under Cr (VI) toxicity, protected NH(4)(+) assimilation and promoted growth of pea by increasing levels of some of the antioxidants i.e., CAT, GR, DHAR, ascorbate and glutathione. Results showed that 10 µM KN increases Cr tolerance while 100 µM KN exhibited opposite responses. These results could contribute to an understanding of the mechanisms of KN-mediated dual influence on metal tolerance in crop plants.

Responses of Pisum sativum L. to exogenous indole acetic acid application under manganese toxicity.

Responses of pea (Pisum sativum L.) seedlings to manganese (50, 100 and 250 µM) and indole acetic acid (10 and 100 µM) treatments were investigated. Single and combined exposure of pea to manganese and 100 µM indole acetic acid decreased root and shoot fresh mass, chlorophyll, carotenoids, protein and nitrogen while ammonium content increased compared to the control. Combined treatment of pea with 250 µM manganese and 100 µM indole acetic acid decreased root and shoot fresh mass by 54% and 51%, chlorophyll and carotenoids by 31% and 26%, root and shoot protein by 47% and 44%, and root and shoot nitrogen by 44% and 40%, respectively. Activities of glutamine synthetase and glutamate synthase were decreased by the exposure of manganese and 100 µM indole acetic acid while glutamate dehydrogenase activity increased. Combined application of 250 µM manganese and 100 µM indole acetic acid decreased root and shoot glutamine synthetase activity by 44% and 39%, and glutamate synthase activity by 39% and 37% while root and shoot glutamate dehydrogenase activity increased by 47% and 42%, respectively compared to the control. In contrast, application of 10 µM indole acetic acid together with manganese decreased the negative impacts of manganese, and promoted seedling growth compared to the manganese treatments alone. This study has shown that 10 µM indole acetic acid protected pea seedlings appreciably from manganese toxicity by regulating ammonium content and the activities of enzymes of ammonium assimilation, while 100 µM of indole acetic acid exhibited opposite response under manganese toxicity.