Growth Responses and Leaf Antioxidant Metabolism of Grass Pea ( Lathyrus sativus L.) Genotypes under Salinity Stress

Abstract

Response of six improved grass pea genotypes to prolonged salinity stress was investigated on seedlings grown in pot experiment using 150 mM NaCl up to 60 days of growth after commencement of treatment (DAC). NaCl exposure significantly reduced growth potential of varieties PUSA-90-2 and WBK-CB-14, but no such effect was observed in varieties B1, BioL-212 and in two mutant lines LR3 and LR4. A time-bound measurement at 15, 30 and 60 DAC revealed significant reduction in plant dry matter production, orchestrated through abnormally low capacity of leaf photosynthesis accompanied by low K + /Na + ratio and onset of oxidative stress in all six genotypes at 15 DAC and the extension of the phenomena in PUSA-90-2 and WBK-CB-14 to 60 DAC. High superoxide dismutase (SOD) activity coupled with low ascorbate redox and declining ascorbate peroxidase (APX) and catalases (CAT) levels led to abnormal rise in H 2 O 2 content at reproductive stage (30 DAC) in the latter two genotypes, consequently, resulting in NaCl-induced oxidative damage. H 2 O 2 level in the rest of the four genotypes was modulated in a controlled way by balanced action of SOD, APX and CAT, preventing oxidative damage even under prolonged NaCl-exposure. Enzyme isoforms were involved in regulation of foliar H 2 O 2 -metabolism, which was critical in determining As tolerance of grass pea genotypes.