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The present study was carried out to determine the effect of chilling stress on mung bean [Vigna radiata (L.) Wilczek], and the possible mediatory role of applied 5-aminolevulinic acid (ALA) on osmotic adjustment and antioxidant system. The increased accumulation of superoxide radical, hydrogen peroxide, and malondialdehyde during chilling stress indicates an enhanced oxidative stress. The chilling stress induced an enhancement of reduced or oxidized glutathione and ascorbic acid, and improvement of superoxide dismutase (SOD), peroxidase (POD), glutathione reductase (GR), and ascorbate peroxidase (APX) activities, but the activity of catalase (CAT) declined. Exogenous ALA enhanced the content of glutathione and ascorbic acid and elevated the antioxidant enzyme activities (POD, SOD, GR, and APX), which improved reactive oxygen species scavenging. In addition, an increased content of osmoprotectants including soluble sugars, soluble proteins, and proline contributed to ROS detoxification and enzyme/protein stabilization. Thus, ALA had a positive effect in improving the chilling resistance of mung bean plants. [ABSTRACT FROM AUTHOR]

The current study investigates a possible mediatory role of uniconazole in improving chilling stress tolerance in chillingsensitive (Hefeng 50) and chilling-tolerant (Kenfeng 16) soybean varieties. Chilling stress decreased photosynthetic pigments and inhibited net photosynthetic rate which was ascribed to stomatal limitation. The maximum quantum efficiency of PSII primary photochemistry and electron transport rate were lower in uniconazole-treated plants compared with the control. The increased contents of superoxide (O2 •-) and malondialdehyde during chilling stress indicated oxidative stress. Chilling stress reduced glutathione and ascorbic acid contents, and promoted peroxidase, glutathione reductase, and ascorbate peroxidase activities. Uniconazole improved the tolerance of chilled plants. This might be due to better antioxidant defense mechanisms including higher contents of antioxidants and activities of antioxidant enzymes, which retard lipid peroxidation. Thus, uniconazole has a positive effect and improves the chilling resistance of soybean. [ABSTRACT FROM AUTHOR]