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2 Acta Physiologiae Plantarum

2 2011

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Modification of chromium (VI) phytotoxicity by exogenous gibberellic acid application in Pisum sativum (L.) seedlings

100%

Gangwar S. , Singh V. P. , Srivastava P. K. , Maurya J. N.

Acta Physiologiae Plantarum

2011

tom 33

nr 4

Effects of exogenous gibberellic acid (GA; 10 and 100 µM) application on growth, protein and nitrogen contents, ammonium (NH₄⁺) content, enzymes of nitrogen assimilation and antioxidant system in pea seedlings were investigated under chromium (VI) phytotoxicity (Cr VI; 50, 100 and 250 µM). Exposure of pea seedlings to Cr and 100 µM GA resulted in decreased seed germination, fresh and dry weight and length of root and shoot, and protein and nitrogen contents compared to control. Compared to control, Cr and 100 µM GA led to the significant alteration in nitrogen assimilation in pea. These treatments decreased root and shoot nitrate reductase (NR), glutamine synthetase (GS) and glutamine 2-oxoglutarate aminotransferase (GOGAT) activities (except 50 µM Cr alone for GOGAT) while glutamate dehydrogenase (GDH) activity and NH₄⁺ content increased. Compared to control, the root and shoot activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) increased (except APX activity at 250 µM Cr + 100 µM GA) while catalase (CAT), glutathione reductase (GR) and dehydroascorbate reductase (DHAR) activities were decreased (except GR at 100 µM GA alone) following exposure of Cr and 100 µM GA. Total ascorbate and total glutathione in root and shoot decreased by the treatments of Cr and 100 µM GA while their levels were increased by the application of 10 µMGA compared to Cr treatments alone. It has been reported that application of 10 µM GA together with Cr alleviated inhibited levels of growth, nitrogen assimilation and antioxidant system compared to Cr treatments alone. This study showed that application of 10 µM GA counteracts some of the adverse effects of Cr phytotoxicity with the increased levels of antioxidants and sustained activities of enzymes of nitrogen assimilation; however, 100 µM GA showed apparently reverse effect under Cr phytotoxicity.

Differential responses of pea seedlings to indole acetic acid under manganese toxicity

100%

Gangwar S. , Singh V. P. , Prasad S. M. , Maurya J. N.

Acta Physiologiae Plantarum

2011

tom 33

nr 2

Present study showed the responses of pea seedlings to exogenous indole acetic acid (IAA; 10 and 100 µM) application under manganese (Mn; 50, 100 and 250 µM) toxicity. Manganese and 100 µM IAA alone as well as in combination decreased growth of pea seedlings compared to control. Moreover, some parameters of oxidative stress—hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) were also increased by single and combined treatments of Mn and 100 µM IAA compared to control. In contrast, addition of 10 µM IAA together with Mn, alleviated Mn toxicity symptoms and promoted growth led to the decrease in H₂O₂ and MDA levels compared to Mn treatments alone. Under single and combined treatments of Mn and 100 µM IAA, catalase activity decreased while superoxide dismutase and ascorbate peroxidase activities increased and glutathione reductase and dehydroascorbate reductase exhibited differential responses. However, addition of 10 µM IAA together with Mn, increased activities of studied enzymatic antioxidants. Root and shoot reduced ascorbate (AA) and reduced glutathione (GSH) and, their reduced/oxidized ratios decreased while dehydroascorbate (DHA) and oxidized glutathione (GSSG) contents increased compared to control following single and combined treatments of Mn and 100 µM IAA. However, supply of 10 µM IAA together with Mn, increased AA and GSH, and their reduced/oxidized ratios in root and shoot compared to Mn treatments alone. This study thus suggests that 10 µM of IAA was able to increase Mn tolerance in pea seedlings under Mn toxicity while opposite was noticed for 100 µM IAA.