Kinetin Regulates UV-B-Induced Damage to Growth, Photosystem II Photochemistry, and Nitrogen Metabolism in Tomato Seedlings

• Published in: Journal of plant growth regulation 2018-03, Vol.37 (1), p.233-245
• Main Authors: Bashri, Gausiya, Singh, Madhulika, Mishra, Rohit Kumar, Kumar, Jitendra, Singh, Vijay Pratap, Prasad, Sheo Mohan
• Format: Article
• Language: English
• Subjects: Agriculture; Biomedical and Life Sciences; Carbonic anhydrase; Carbonic anhydrases; Chlorophyll; Cytokinins; Fluorescence; Glutamate dehydrogenase; Glutamate-ammonia ligase; Glutamine; Growth regulators; Kinetin; Life Sciences; Metabolism; Nitrate reductase; Nitrite reductase; Nitrogen; Nitrogen metabolism; Oxygen uptake; Parameters; Photochemistry; Photosynthesis; Photosystem II; Pigments; Plant Anatomy/Development; Plant growth; Plant Physiology; Plant Sciences; Radiation damage; Respiration; Respiratory rate; Seedlings; Tomatoes; Ultraviolet radiation; Water splitting
• ISSN: 0721-7595; 1435-8107
• DOI: 10.1007/s00344-017-9721-7

Cytokinins are a class of plant growth regulators that regulate several developmental processes in plants, and recently their role in counteracting the deleterious effects of abiotic stresses has been noted. The impacts of kinetin (10 µM, KN; an artificial cytokinin) on growth, photosystem II photochemistry, and nitrogen metabolism in tomato seedlings exposed to two levels (UV-B 1 , ambient+ 1.2 kJ m −2 day −1 , and UV-B 2 , ambient+ 2.4 kJ m −2 day −1 ) of enhanced UV-B radiation were analyzed under open field condition. The growth, pigment contents, carbonic anhydrase activity, photosynthetic O 2 yield, and values of chlorophyll a fluorescence parameters: F v / F 0 , F v / F m or φ P 0 , ψ 0 , φE 0 , and PI ABS declined, whereas the values of energy flux parameters (ABS/RC, TR 0 /RC, ET 0 /RC, and DI 0 /RC) of PS II, efficiency of water splitting complex ( F 0 / F v ), and respiratory rate of O 2 uptake increased under UV-B stress. Likewise, UV-B exposure at both doses significantly inhibited the activity of enzymes involved in nitrogen metabolism: nitrate reductase, nitrite reductase, glutamine synthetase, and glutamate synthase. In contrast, an enhancing effect on glutamate dehydrogenase activity was observed under UV-B stress. Exogenous KN resulted in a significant attenuation in UV-B-induced negative effects on growth, pigments, photosynthesis, and nitrogen metabolism. The study concludes that exogenous KN improved the growth performance of tomato seedlings by attenuating the damaging effects of UV-B radiation on photochemistry of PS II and nitrogen metabolism, and the alleviating effect against the low dose (UV-B 1 ) of UV-B was more pronounced.