Effect of Low Light Stress on Photosynthetic Pigments and Antioxidative Enzymes in Field Grown Indian Mustard (Brassica juncea L.) Genotypes

: Oilseed Brassicas have prominent place after soybean and groundnut. More than 90% of the area under oilseed Brassicas is occupied by the Indian mustard ( Brassica juncea ) because of its relative tolerance to biotic and abiotic stresses as compared to other oilseed Brassica species. Light plays key a role in net primary productivity and is necessary for plant growth , morphogenesis and several physiological processes. The present investigation aimed to assess the effect of low light stress on photosynthetic traits and antioxidative enzymes in Brassica juncea genotypes. Shading was imposed with nets from mid-December to mid-January which cut 25%-30% of natural sunlight. Shading period coincided with the onset of flowering. The results showed that chlorophyll b and antioxidant activities of superoxide dismutase (SOD), guaiacol-peroxidase (G-POD) and catalase (CAT) increased under low light stress at two stages of investigations (10 and 30 days after removal of nets). With shading treatment, soil plant analysis development (SPAD) chlorophyll meter values, chlorophyll a , total chlorophyll, chlorophyll a / b ratio, carotenoid and protein content decreased significantly while malondialdehyde content increased due to damages of plant cells. This study provides valuable information for further deciphering genetic mechanism and improving agronomic traits in Indian mustard cultivated under optimal light requirements.