ABSTRACT
Aim: This study aims at exploring the interactive effect of salinity, a known inhibitor of plant growth,and salicylic acid (SA), a growth promoter, on niger [Guizotia abyssinica (L.f.) Cass], an oilseed crop plant, by assessing its growth, metabolism and defence system. Methodology: In a pot experiment, 4-week-old seedlings of niger were treated with NaCl (50, 100 and 150 mM added to the soil) and SA (1 mM aqueous solution sprayed on foliage) and watered regularly with 100% field capacity. A total of 8 treatments, including the control, were maintained for 8 weeks. Nine-week-old seedlings were sampled to analyze the growth attributes, plant water status, photosynthetic traits, lipid-peroxidation level, and activity of antioxidant enzymes. Results: Salinity treatments inhibited plant growth significantly, as evident from a dose-dependent reduction in size and biomass of roots and shoots. The reduction in stem basal diameter was significant only with 150 mM NaCl, a dose which also induced oxidative stress and enhanced lipid peroxidation. Salinity also reduced photosynthetic efficiency by inhibiting chlorophyll synthesis, nitrate reductase activity, chlorophyll fluorescence, stomatal conductance, net photosynthetic and transpiration rates, and plant water status. Reduction in relative water content was significant only at 150 mM of NaCl. High salinity also increased proline production and activity of antioxidant enzymes. Application of SA alone usually caused positive but non-significant effects on photosynthesis and growth parameters. SA application in combination with salt stress mitigated the salinity-induced adverse effects on growth and photosynthetic attributes. Moreover, upregulation of antioxidant enzymes evoked by salinity was further enhanced. Interpretation: Salinity hampered the overall performance of the crop, but SA application fortified its salt-tolerance capacity by alleviating the membrane injury and improving the assimilatory activities, plant water status and defense arsenal, thus reducing the adverse effects of salt stress on foliar functions and plant growth.
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 H2O2 content, lipid peroxidation (TBARS), free radical quenching systems (nonenzymatic and enzymatic antioxidants) and ion accumulation in different plant parts under NaCl and CaCl2 stress. Fifteen-day-old seedlings were treated with solutions of 25 mM (T1 ), 50 mM (T2 ) and 100 mM (T3 ) NaCl alone and in combination of 10 mM CaCl2 i.e., 25 mM + 10 mM (T4 ), 50 mM + 10 mM (T5 ) and 100 mM + 10 mM (T6 ). 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, H2O2 content and lipid peroxidation (TBARS) in leaves were enhanced, consequently invoking the activities of SOD, APX, GR and CAT. Application of NaCl + CaCl2 alleviated adverse effects of NaCl stress. The Na+ and Cl- contents in different plant parts increased with NaCl as well as with NaCl + CaCl2 treatments. The maximum accumulation occurred in roots, followed by the stem and the leaves. The K+ and Ca2+ contents decreased under NaCl stress; but NaCl + CaCl2 treatment reduced the extent of decrease caused by NaCl. Thus, calcium ameliorated the deleterious effects of NaCl stress and stimulated plant metabolism and growth.