STM Article Repository

The present study was conducted to understand the biochemical changes in rice (Oryza sativa L.) genotypes viz., heat tolerant (N22), moderately heat susceptible (IR8) and fine grain rice variety (PR116) in response to different transplanting time. Constitutive level of phenylalanine ammonia lyase (PAL), tyrosine ammonia lyase (TAL) was found to be significantly higher in N22 than in IR8 at very early (D1) and early transplanting (D2) times. Heat stress caused a significant increase in the level of the phenolics constituents. Total free amino acid were significantly higher in N22 than in PR116 and IR8. Total sugars and reducing sugars decreased at D1 and maximum content was found in IR8. The starch content was found to be maximum in N22. Total amino acid content showed an increase with increase in heat stress in IR8 and PR116. Higher expression of PAL, TAL and phenolic constituents in N22 is suggestive of their significant role in development of tolerance exhibited by the cultivar N22 under heat stressed conditions.