Archive | 2021
Effects of exogenous melatonin on plant growth, root hormones and photosynthetic characteristics of trifoliate orange subjected to salt stress
Abstract
\n Soil salinity has negative effects on crop growth and production, and melatonin (MT) plays an important role in regulating the salt stress of plants. However, it is not clear whether exogenous melatonin mitigates the negative effect on citrus plants subjected to salt stress. This study was to explore the response of exogenous melatonin (0, 50, 100, 150 µmol/L) on plant growth, root hormone levels and photosynthetic system of trifoliate orange (Poncirus trifoliata) seedlings exposed to 0, 150 mmol/L NaCl for 4 weeks. The 150 mmol/L NaCl treatment significantly increased root zeatin riboside and gibberellin levels, while dramatically inhibited plant height, root auxin level, leaf photosynthesis and fluorescence indexes of seedlings. However, melatonin seedlings represented greater growth performance and dry matter quality under non-salt and salt stress. Furthermore, the effects of NaCl stress on the net photosynthetic rate, stomatal conductance, maximum photochemical efficiency, PSII effective photon yied, photochemical quenching and other indicators of seedlings leaves were effectively alleviated and the damage of NaCl stress was also reduced when seedlings were treated with melatonin. It suggests that exogenous melatonin had positive effects on enhancing salt tolerance of trifoliate orange seedlings, which is involved in greater plant growth, higher auxin level, and stronger photosynthetic physiology, and 100 µmol/L melatonin concentration has the best result.