Effects of melatonin on photosynthesis and soybean seed growth during grain filling under drought stress

Abstract

We studied the effects of melatonin on soybean photosynthesis and seed growth at different developmental stages under drought stress induced by polyethylene glycol in the growth medium. Experimental groups were supplied with a normal nutrient solution after seven days of continuous treatment; overall, five treatments were completed when the early maturity stage was reached. Under normal water supply, melatonin supplementation had no significant effect on the photosynthetic characteristics or soybean seed growth. However, drought stress reduced leaf relative water content, chlorophyll content, and relative photosynthetic gas-exchange parameters, while it increased a leaf content of osmoregulatory substances, antioxidant-related enzyme activities, and seed growth-related indicators. Compared to the drought-stressed group, the melatonin treatment under drought stress improved the above indicators; specifically, melatonin effectively increased the photosynthetic rate, 100-seed mass, and total seed mass per plant. All the effects were most significant during the first seven days after the early seed-filling stage.

Melatonin-Induced Water Stress Tolerance in Plants: Recent Advances

“…Melatonin treatment ranges from a very low concentration (50 nM) in grape [ 33 ] to a high dosage (1 mM) in maize [ 34 ] ( Table 1 ). Moreover, melatonin can be applied in different forms to alleviate drought stress, including seed priming [ 35 ], seed coating [ 36 ], direct soil treatment [ 37 ], foliar application [ 32 ], in nutrient solutions and hydroponic systems [ 38 ], supplemented with irrigation [ 27 ], and roots pretreatment [ 39 ] ( Table 1 ).…”

“…In this respect, melatonin enhances plant resistance via higher stomatal conductance [ 42 ], higher cell turgor and water holding capacity [ 65 ], and stomatal opening regulation [ 77 ]. Consequently, the whole plant status is enhanced, including seed germination efficiency [ 47 ], root generation vitality and strength [ 61 ], growth and flowering [ 36 , 50 ], visual quality [ 65 ], seed yield [ 38 ], leaf senescence alleviation [ 54 ], and quick recovery after rehydration [ 59 ].…”

Changes in photosynthetic and chlorophyll fluorescence characteristics of sorghum under drought and waterlogging stress

“…Moreover, excessive soil moisture (EM) has been shown to reduce stomatal conductance (gs), transpiration (E), photosynthetic rate (PN), and other physiological parameters of dry land crops such as corn (Zea mays L.) (Zaidi et al 2003) and winter wheat (Triticum aestivum L.) (Abid et al 2018). Many researchers have pointed out that water stress can cause leaf stomatal closure and decrease intercellular CO2 concentration (Ci), available CO2 concentration in mesophyll cells, and carbon assimilation (Zou et al 2019). This is due to a decline in photosynthetic rate and a reduction in biomass accumulation (Gomes-Laranjo et al 2006).…”

Melatonin-induced Water Stress Tolerance in Plants: Recent Advances

“…Melatonin treatment ranged from a very low concentration (50 nM) in grape [34] to high dosage (1 mM) in maize [35] (Table 1). Moreover, melatonin can be applied as different forms to alleviate drought stress including seed priming [36], seed coating [37], direct soil treatment [38], foliar application [33], in nutrient solutions and hydroponic systems [39], supplemented with irrigation [28] and roots pretreatment [40] (Table 1)…”

“…In this respect, melatonin enhances plant resistance via higher stomatal conductance [43], higher cell turgor and water holding capacity [65], and stomatal opening regulation [78]. Consequently, the whole plant status is enhanced including seed germination efficiency [48], root generation vitality and strengthen [61], growth and flowering [37,51], visual quality [65], seed yield [39], leaf senescence alleviation [55] and quickly recovering after rehydration [59].…”