Alterations in onion (allium cepa L.) provoked by salinity and its alleviation using phosphorus

A soil pot culture experiment was carried out in wire house condition to investigate the response of Onion (Allium cepa cv. N-53) grown in saline water and amended with supplementary Phosphorus (P). Plants were subjected to different electrical conductivity (EC) solution viz. 0, 2, 4, 6 and 8 dS/m prepared by mixing NaCl, Na2SO4, CaCl2 and MgCl2. For remediation approach two salinity levels (EC 6 and 8 dS/m) were subjected with combination of 40ppm Phosphorus. The results demonstrated that salt stress hampered the plant growth such as fresh and dry weight of plant. Increased accumulation of malondialdehyde content in the leaf of plant exposed to salty solution suggested that salinity promoted the oxidative stress. The other stress indicator parameters such as enzymatic and non enzymatic antioxidant were also analyzed. The non-protien thiol group was found to gradually enhance at lower doses and decreased at higher salinity levels (8EC) and cysteine increased at all salinity levels. Phosphorus application comparatively (salt treated plants) decreased the content of cysteine and NP-SH in the leaf of plant treated with salt +P as salinity level rose. Salt stress were also declined pigment contents like Chl T, Chl a, Chl b and Carotenoids and the activity of catalase (CAT) and peroxidase (POX) but P amendment increased their activity. Activity of ascorbate peroxidase (APX) and glutathione reductase (GR) were found to increase at lower levels of salinity while decreased at higher levels. In this study activity of superoxide dismutase (SOD) was increased at all tested salinity levels while P supply decreased activity. The results indicated that supplementary P can mitigate the negative influence of water salinity on plant growth and physiological development.