Abstract
Seeds of three rice (Oryza sativa L.) genotypes Viz. IR-42 (intolerant), USAR-1 and NDR-501(Tolerant) were germinated in Petri-dishes containing aqueous solution of NaHCO3 at pH of 8.5, 8.8, and 9.2 at 30+1°C in seed germinator. Seed kept for germination on distilled water served as control. Nitrate reductase (NR), Nitrite reductase (NiR) and Glutamine synthetase (GS) activities were assayed in embryonic axis after 72, 96 and 120 h, respectively after soaking. Nitrate reductase (NR) and nitrite reductase were higher in USAR-1 fallowed by NDR-501 and IR-24 respectively under normal condition. Glutamine synthetase activity on the other hand, was maximum in NDR-501 and minimum in IR-24. Activities of the entire enzyme increased with growth stage but decreased progressively with increasing level of alkalinity, though the magnitude of reduction was more in intolerant genotype IR-24. Enzymes activity in the tolerant genotype under normal as well as alkaline condition was higher and might be due to their better equipped salt tolerant mechanism. Glutamine synthetase being one of the key regulatory enzymes of nitrogen metabolism. It linked with the molecular basis of salt tolerance in rice genotypes and providing certain degree of protection against hostile environment. Key words: Alkalinity, glutamine synthetase, nitrate reductase, nitrite reductase, and rice.
Highlights
Soil alkalinity is one of the major problems in part of India as well as world for rice production
Soil alkalinity and salinity are the complex and two different abiotic stresses which is caused by high amount of Na2CO3 or NaHCO3 and NaCl or NaSO4 respectively
Proper and efficient nitrogen metabolism is crucial for salt tolerance
Summary
Nitrate reductase (NR), Nitrite reductase (NiR) and Glutamine synthetase (GS) activities were assayed in embryonic axis after 72, 96 and 120 h, respectively after soaking. Nitrate reductase (NR) and nitrite reductase were higher in USAR-1 fallowed by NDR-501 and IR-24 respectively under normal condition. Enzymes activity in the tolerant genotype under normal as well as alkaline condition was higher and might be due to their better equipped salt tolerant mechanism. Glutamine synthetase being one of the key regulatory enzymes of nitrogen metabolism. It linked with the molecular basis of salt tolerance in rice genotypes and providing certain degree of protection against hostile environment
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