Author(s):

Sareeta Nahakpam

Abstract: The present work was carried out in fourteen rice genotypes of same maturity group and showing partial tolerance to drought stress at early flowering stage. Besides, variations in root morphological traits, genotypic specificity cannot be underestimated. RL (root length) got increased in all the genotypes under drought stress as compared to control. RDM (root dry matter), root:shoot ratio, SRL (specific root length), RMF (root mass fraction) determined genotypic specificity in the response towards drought. Root RWC (Relative water content) of genotypes BRR-0028, BRR-0026 and Sabour Ardhjal showed maximum with 88%, 87% and 86% respectively. Moreover, the RWC percent is greater in leaves from that of root revealing either translocation capacity of water from roots to shoots or alteration of leaf stomatal conductance during drought situation. This had been encouraged by higher accumulation of proline content in the genotypes with potentials of osmotic adjustment whereby genotypes BRR-0028 was found to be maximum with 54.32 µg g^-1dry wt. Drought induced in decreasing photosynthetic rate and stomatal conductance thereby increasing the rate of transpiration. However, the results also lighted on better performances of genotypes in drought than that of control. Correlation study showed the root traits had command over physiological parameters of above ground part of the plant. For instance, strong positive correlation of RL and SRL with stomatal conductance at p< 0.01 whereby further interrelating with shoot length, and then to photosynthesis rate and transpiration rate at p< 0.05. The root mass study showed a non significant negative correlation with photosynthesis rate and stomatal conductance which probably an indication of increasing availability of assimilates for aboveground parts especially leaves during early reproductive phase drought. Findings were the evidence for root tempering changes in above ground shoot physiological traits under drought.

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