Possible role of molecular mass of medium supplemented phenolics in improving rice growth in puddled saline condition

Abstract

Phenolics are a large class of compounds with wide ranging molecular mass and physiological effects for plants. By virtue of their antioxidative action, they may improve salt tolerance in rice. In this research, the effect of medium supplementation (0.25 mM) of each of salicylic acid (SA; a low molecular mass) and tannic acid (TA; a high molecular mass) phenolics was studied under control and 150 mM NaCl salt level on growth, leaf photosynthetic pigments, leaf gas exchange and nutrients contents of KS-282 (coarse) and Basmati-515 (fine) rice (Oryza sativa L.). Salt stress reduced the leaf photosynthetic pigments, gas exchange and tissue concentration of nutrients in shoot and root. Medium supplementation of TA and SA alleviated the salinity effects and effectively recuperated the rice growth by increasing the synthesis of metabolites (free proline, anthocyanins, soluble sugars and soluble phenolics) and accumulation of essential nutrients NO3--N, PO43--P, Ca2+ and K+ and reduction in tissue Na+ contents more in the root than leaf and affirmed greater role of the TA than SA in bringing about positive changes in the leaf and root tissues. Coarse rice (KS-282) responded better than fine rice (B-515) towards medium supplemented phenolics than fine rice under salinity stress. A greater effectiveness of TA than SA under salt stress could be attributed to the difference in their molecular arrangement (TA a polyphenol and SA a monophenol).

Keywords

• Salinity
• free proline
• molecular mass
• root growth
• gas exchange
• polyphenol