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Exogenous melatonin promotes biomass accumulation and photosynthesis of kiwifruit seedlings under drought stress

Liang, Dong, Ni, Zhiyou, Xia, Hui, Xie, Yue, Lv, Xiulan, Wang, Jin, Lin, Lijin, Deng, Qunxian, Luo, Xian
Scientia horticulturae 2019 v.246 pp. 34-43
absorption, biomass production, carbon dioxide, carbon dioxide fixation, cell membranes, dose response, drought, drought tolerance, electron transfer, energy, gene expression regulation, genes, irrigation, kiwifruit, lipid peroxidation, melatonin, photosystem II, plant growth, proteins, ribulose-bisphosphate carboxylase, root systems, seedlings, stomatal movement, transcription (genetics), water stress
Melatonin is involved in regulating plant growth and responding to multiple environmental stresses. The underlying mechanism by which melatonin mediates drought tolerance in some plant species remains unknown. We investigated the effects of melatonin with different doses (50, 100, and 200 μM) on growth and photosynthesis in kiwifruit (A. chinensis var. deliciosa cv. Qinmei) seedlings under drought stress. Drought stress strongly suppressed biomass accumulation, damaged cellular membranes, and inhibited photosynthesis in the seedlings. However, irrigation with melatonin mitigated the drought-induced impairment in a dose-dependent manner, with the greatest efficiency provided by 100 μM. Melatonin promoted the development of the root system architecture, reduced lipid peroxidation and pigment degradation, alleviated injuries to cell membranes, promoted the accumulation of osmotica, and inhibited the degradation of or facilitated synthesis of certain proteins. In addition, melatonin improved photosynthesis by inhibiting stomatal closure, enhancing light energy absorption, and promoting electron transport in PSII. Moreover, transcription of 11 genes for enzymes involved in CO2 fixation (Rubisco, PGK, GAPA, FBA, FBP, TIM, TKT, RPK, SEBP, RPI, and RPE) was upregulated in response to melatonin. These results demonstrate that supplemental melatonin could effectively ameliorate the repression of biomass accumulation and photosynthesis caused by drought and thus enhance the seedlings adaptability to drought stress.