Author(s):

Sareeta Nahakpam

Abstract: Results suggest variation in stress response with the type of stress is given either singly or in combination of Cd²⁺ and heat to seedlings of rice cvs. DR-92 and Bh-1. Increased production of H₂O₂ and O₂^.- levels showed higher under combined stress. Elevated levels of TBARs indicated membrane damage in both roots and shoots. Maximum level of total soluble protein were noted under 100 μM Cd²⁺ + heat stress in cv. Bh-1 and in 500 μM Cd²⁺ + heat stress in cv. DR-92 at 15 day of growth. The study revealed an altered protein level under Cd²⁺ toxicity alone and Cd²⁺ + heat stress. Synthesis of stress specific LMW (20 to 60 kDa) and HMW ( 90 to 200 kDa) proteins under Cd²⁺, heat and Cd²⁺ + heat stress were recorded in both the rice cultivars. In cv. DR-92 five new protein bands (S1-S5) were present in shoots under 500 μM Cd²⁺ + heat treatments. In roots of cv. DR-92 two new protein bands R1 (HMW, ~90-100 kDa) and R2 (LMW, ~55-58 kDa) were present under 10 μM Cd²⁺ + heat treatments. The induction of both HMW and LMW and an increase in the intensity of already existing proteins under combined effect of Cd²⁺ and heat stress suggest the involvement of both constitutive and inducible cytosolic proteins in stress combating phenomenon. Of the two rice cultivars cv. Bh-1 appears to better adapted to Cd²⁺ stress alone as well as in combination with heat stress, than cv. DR-92.

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