Biochemical evaluation of irrigated flooded transplanted and aerobic rice (Oryza sativa L.)
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Date
2014
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PAU
Abstract
Aerobic rice offers an attractive alternative approach over transplanting system as it uses less water with low labour expenses. Ten rice cultivars viz. PR 120, PR 115, PR 116, Feng Ai Zaan, Vandana, IR 71701-28-1-4, PAU 201, Punjab Mehak 1, MAS 946 and UPLRi 7 were extensively characterised for biochemical and physiological parameters under lab and field conditions. In flag leaf and grains, activities of antioxidative enzymes viz. ascorbate peroxidase (APx), guaiacol peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD) along with polyamine oxidase (PAO) and contents of ascorbate, α-tocopherol and polyamines increased gradually till mid milky stage and thereafter declined towards maturity under both planting conditions. Transplanted conditions led to higher activities of antioxidative enzymes (APx, GPx, CAT) alongwith contents of ascorbate, α-tocopherol in PR 116, PAU 201 and Punjab Mehak 1 whereas aerobic condition had elevated levels of the PAO, SOD activities and contents of polyamines, lipid peroxide and hydrogen peroxide in Feng Ai Zaan, PR 115 and PR 120 cultivars which indicated differential response of cultivars and their superior tolerance mechanism. Contents of total sugars, reducing sugars and sucrose alongwith activities of sucrose synthase (cleavage) and invertase (acid and neutral) first increased gradually till anthesis in leaf and 14 days post anthesis in grains and thereafter declined towards maturity under both planting conditions. Similar to antioxidant defense and polyamine metabolism, aerobic conditions significantly decreased activities of invertases (acid and neutral) and sucrose synthase cleavage along with decrease in yield and starch content in all cultivars. In contrast, activities of sucrose synthase/phosphate synthase and soluble protein content increased in conjunction with an increase in the amino acids content under aerobic conditions. Our results reveal variable response of antioxidant, amine oxidase and sucrose metabolising enzymes within genotypes under two planting conditions. Diminished activities of antioxidant enzymes and contents of antioxidants, and other metabolites viz. sugar, starch and protein were exhausted to combat water stress. Based on the results, we infer that antioxidative defense mechanism in transplanted rice and polyamine metabolism in direct-seeded ones led to enhanced tolerance for their survival. This differential response of genotypes under two planting conditions give a clear indication that metabolic pathway differ under two planting conditions to counteract reactive oxygen species generated during stress conditions in aerobic rice.
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Keywords
enzymes, rice, planting, irrigation, developmental stages, biological phenomena, proteins, grain, sucrose, antioxidants