Halo- and UV-B priming-mediated drought tolerance and recovery in rice seedlings

Abstract

Drought stress is a major stress constraint for the growth and establishment of rice seedlings. The objective of this study was to investigate the effects of UV-B and halo priming induced physiochemical changes in the seedling stage of drought-sensitive rice variety exposed to drought stress and recovery. The seedlings of Oryza sativa L. var. Neeraja were UV-B and halo primed and was further subjected to drought stress and recovery. Drought stress induced reactive oxygen species leads to the accumulation of carbonyl content indicating the impairment of photosynthetic machinery and various cellular activities. However, the seed priming resulted in the enhanced production of various metabolites such as proline, amino acids, soluble protein, total phenolics and total soluble sugar. Moreover, it increased the activities of antioxidant enzymes such as superoxide dismutase, catalase and ascorbate peroxidase in rice seedlings exposed to drought stress. After re-watering, all the increased physiochemical parameters of primed and non-primed rice seedlings returned to the levels as in control. The retention of priming memory in seedlings emerged from primed seeds make them more tolerant towards drought and rapid recovery occurs in response to re-watering. Thus, these results suggest that halo and UV-B priming of Oryza sativa seeds is an effective means for reducing drought stress impacts and enhancing the recovery rate from drought at the seedling stage .