UV radiation priming: A means of amplifying the inherent potential for abiotic stress tolerance in crop plants

The emerging concept, that agricultural crops become more hardy on exposure to low levels of UV radiation, has directed the thoughts towards utilizing the same for priming the seeds/seedlings of crop plants to counter abiotic stresses. The exposure of seeds to UV is an ecologically safe method to improve plant productivity, yield quality and also to enhance the tolerance of plants to various biotic and abiotic stresses. According to various researchers, the seeds and seedlings of different plants (rice, wheat, maize, cucumber, cowpea) when irradiated with low levels of UV radiation (0.004-4 Wm(-2) from UV lamp with cellulose diacetate filters) lead to various morphological and physiological changes in the further growth stages. Low levels of UV irradiation also stimulated the seed germination, growth, biomass, seed coat thickness, fresh and dry weight of roots and shoots. Moreover, the pigment content like carotenoids, anthocyanins, chlorophyll and also the photosynthesis were increased on exposure to low levels of UV irradiation. Priming of seeds or seedlings with low levels of UV radiation not only stimulated production of various metabolites, but also enhanced the activities of antioxidant enzymes and accumulation of non enzymatic antioxidants and thus enhances tolerance of plants towards various abiotic stresses. UVB photoreceptor (UVR8) has been isolated from Arabidopsis, which regulates the expression of gene in UVB acclimation and stress tolerance. Thus low levels of UV may be imparting a priming effect on various crop species, so as to bring about positive changes with regard to biotic and abiotic stress tolerance, enhanced crop yield and quality. (C) 2017 Elsevier B.V. All rights reserved.