Article

Calcium interaction with salinity-induced effects on growth and metabolism of soybean (Glycine max L.) cultivars

Journal of Environmental Biology (Impact Factor: 0.68). 01/2010; 31:795-801.

ABSTRACT In the present work, hydroponic culture of JS-335 and Bragg cultivars of soybean (Glycine max) were raised to analyze changes in growth, reactive oxygen metabolism in terms of H 2 O 2 content, lipid peroxidation (TBARS), free radical quenching systems (non-enzymatic and enzymatic antioxidants) and ion accumulation in different plant parts under NaCl and CaCl 2 stress. Fifteen-day-old seedlings were treated with solutions of 25 mM (T 1), 50 mM (T 2) and 100 mM (T 3) NaCl alone and in combination of 10 mM CaCl 2 i.e., 25 mM + 10 mM (T 4), 50 mM + 10 mM (T 5) and 100 mM + 10 mM (T 6). Observations recorded at 30 days after sowing displayed significant decreases in plant biomass, leaf water potential, leaf area, chlorophyll content and the contents of glutathione (GSH) and ascorbate (AsC) on application of NaCl alone. However, H 2 O 2 content and lipid peroxidation (TBARS) in leaves were enhanced, consequently invoking the activities of SOD, APX, GR and CAT. Application of NaCl + CaCl 2 alleviated adverse effects of NaCl stress. The Na + and Cl -contents in different plant parts increased with NaCl as well as with NaCl + CaCl 2 treatments. The maximum accumulation occurred in roots, followed by the stem and the leaves. The K + and Ca 2+ contents decreased under NaCl stress; but NaCl + CaCl 2 treatment reduced the extent of decrease caused by NaCl. Thus, calcium ameliorated the deleterious effects of NaCl stress and stimulated plant metabolism and growth. Introduction Abiotic stresses pose a serious threat to agriculture and the natural status of the environment. Salinity affects plant growth and its deleterious effects are attributed to a reduced osmotic potential of the growing medium, specific ion toxicity and nutrient deficiency (Luo et al., 2005; Bhattacharjee, 2008). Low osmotic potential of saline solutions prevents water uptake by plants, resulting in a "physiological drought". Alterations in physiological processes due to osmotic stress cause reduction in growth. Plant dry weights may be drastically reduced (Kim et al., 2009; Ozdener and Kuttbay, 2008). Salinity can cause hyperionic and hyperosmotic effects on plants, leading to membrane disorganization and metabolic toxicity, including the excessive generation of reactive oxygen species (ROS) such as the superoxide anion (O 2 –), H 2 O 2 and the hydroxyl radicals, particularly in chloroplasts and mitochondria (Mittler, 2002). Generation of ROS causes rapid cell damage by triggering a chain of reactions. To protect themselves from the harmful effects of oxidative stress, plants develop ROS-scavenging mechanism that involves detoxification processes carried out by an integrated system of the non-enzymatic reduced molecules, like ascorbate and glutathione, and the enzymatic antioxidants such as superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) (Jaleel et al., 2007). Studies of antioxidant mechanisms may provide clues to enhance salt tolerance in plants.

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