Abstract

Elevated UV-B radiation deleteriously affects rice yields. The impacts of plant growth regulator (PGRs; ?-tocopherol, glycine betaine [GB] and salicylic acid [SA]) applications on higher plants have been the subject of many studies. However, little or no work has been carried out on rice responses to ?-tocopherol, GB or SA under UV-B stress conditions. This study determined the effects of ?-tocopherol (2.3 kg ha^-1), GB (2.0 kg ha^-1) or SA (12.9 g ha^-1) application on rice leaf photosynthetic rate (P_N), photochemistry and physiology under ambient and elevated UV-B conditions. Elevated UV-B decreased P_N (17%), quantum yield (8%), electron transport rate (9%), total chlorophyll concentration (8%), plant height (12%), number of leaves (17%), pollen viability (6%), phenolic concentration (46%) and yield (21%). The applications of Alpha-tocopherol, GB or SA increased yield by 23%, 18% and 29%, respectively, under elevated UV-B. Application of PGRs increased leaf phenolic content thus rendering protection against elevated UV-B.

 

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