Exogenous melatonin improves salt tolerance in tomato by regulating photosynthetic electron flux and the ascorbate–glutathione cycle

Abstract

Melatonin (MT) can protect plants against abiotic stress. In order to explore whether melatonin can improve photosynthetic function under NaCl stress, Solanum lycopersicum L. cv. Liaoyuanduoli were exposed to 150 mmol L −1 NaCl stress with or without pretreatment with 150 μmol L −1 melatonin. The results showed that NaCl stress can lead to reduced chlorophyll content, lower photosynthetic function, increased reaction oxygen species (ROS) levels, and decreased PSII activity. These changes were mainly due to the reduction in oxygen-evolving complex (OEC) activity on the donor side of PSII and the blockage of electron transfer from Q A to Q B on receptor side of PSII. The donor side of PSII was more sensitive to NaCl stress relative to the receptor side of PSII. Interestingly, application of MT enhanced tomato NaCl tolerance. MT reduced the production of ROS by balancing the distribution of photosynthetic electron flux, facilitated the repair of PSII by maintaining the abundance of Psb O and D1, and promoting the ability of the donor and acceptor sides of PSII to deliver electrons. MT also enhanced the scavenging ability of ROS by stimulating the activity of enzymes involved in the AsA-GSH cycle.

Exogenous melatonin enhances salt stress tolerance in tomato seedlings

“…The current study highlights the significant decline in almost all of the growth parameters of plants under salt stress but this decline was significantly alleviated by the exogenous melatonin, which has been proved as a plant growth regulator (Zhang et al 2013). Ke et al (2018), Li et al (2019c), Yin et al (2019), Zafar et al (2019), and Zhang et al (2020) showed that leaf senescence can be delayed by application of melatonin and also plant resistance against cold, drought, salt, and many other abiotic stresses can be enhanced. Results of the current study indicated that growth and biomass production could be effectively increased by 100 µM melatonin (Figs.…”

“…The protective role of melatonin pretreatment has been proved under salinity in many plants. Many studies reported that photosynthesis and chlorophyll content were improved in tomato seedlings (Zhou et al 2016, Yin et al 2019, watermelon seedling (Li et al 2017a), lettuce seedling (Yan et al 2016), and cucumber seedling (Wang et al 2016a, Zhang et al 2020. Under drought, it has been reported by Liu et al (2015a) that antioxidant capacity and photosynthesis of tomato seedlings are enhanced by melatonin treatment.…”

“…Melatonin has multiple functions in plants, though, its possible role under abiotic stresses is still uncertain (Siddiqui et al 2019). Yin et al (2019) described its protective ability against abiotic stress in plants. Li et al (2019b) suggested the involvement of melatonin in enhancing tolerance under both biotic and abiotic stresses in tomato plants, by regulation of several biological processes.…”

Chlorophyll-a Fluorescence Analysis Reveals Differential Response of Photosynthetic Machinery in Melatonin-Treated Oat Plants Exposed to Osmotic Stress

“…Recent studies have demonstrated the protective roles played by melatonin in different plants under different conditions of stress [9,11,[21][22][23][24]. Nevertheless, very few studies have discussed the impact of melatonin on some of the basic photosynthetic parameters under stress conditions [9,10,25].…”

Melatonin Positively Influences the Photosynthetic Machinery and Antioxidant System of Avena sativa during Salinity Stress

“…Moreover, most studies have focused on the ROS scavenging capacity of melatonin; few studies have investigated the effects of melatonin on the photosynthetic machinery, especially under salinity stress. However, very recently, Yin et al [21] have demonstrated the positive effects of melatonin in tomato plants under salt stress. It was found that pre-treatment of melatonin suppressed the production of ROS by establishing a consistent flow of electrons, improving the repair of photosystem II (PSII) by maintaining the abundance of PsbO and D1, and facilitating the ability of the donor and acceptor sides of PSII to deliver electrons.…”