The effect of seed pretreatment and foliar application of melatonin and spermidine on germination and physicochemical traits of kodo (Fagopyum esculentum Moenc) under drought stress

Drought stress is one of the affecting factors on physiological traits in arid and semi-arid regions, especially in Iran. Recently, the role of polyamines has been considered to increasing plant tolerance to stresses, including drought. Polyamines are a new group of growth regulators and are involved in a wide range of physiological and biochemical processes such as stress resistance, phospholipid membrane stability and osmotic regulation (zakai, khosroshahi and duodenal, 2008). The aim of this experiment was to investigate the effect of seed pretreatment and seedling foliar application with melatonin and spermidine on kodo physicochemical traits under drought stress in laboratory and greenhouse.

In this study, experiments were performed in two stages. In the first stage (laboratory), the experiment was performed as a two-factor split factorial in the form of completely randomized blocks with four replications. Experimental treatments including drought stress as the main factor in seven levels of zero osmotic potential (control), -0.2, -0.4, -0.6, -0.8, -1 and -1.2 MPa, pretreatment seeding with spermidine at five levels, zero, 0.5, 1, 1.5 and 2 mM and pre-seeding with melatonin at five levels, zero, 0.125, 0.250, 0.375 and 0.500 mM were sub-factors. After performing the first stage, the best experimental treatments were selected and in the next stage (greenhouse), the experiment was performed as a three-factor split factorial in the form of completely randomized blocks with three replications. Drought stress was the main factor in three levels of irrigation in 10% of field capacity depletion (optimal irrigation), irrigation in 40% of field capacity depletion (mild stress) and irrigation in 70% of field capacity depletion, seed pre-selection as a secondary factor at three levels: no pre-treatment (control), pre-treatment with spermidine, pre-treatment with melatonin and also seedling foliar application was applied as a sub-factor at three levels: no foliar application, spermidine foliar application and solution Spraying with melatonin.

The results showed that concentrations of 1.5 spermidine and 0.375 mM melatonin had the highest percentage and germination rate. In the greenhouse, experimental treatments showed a significant effect on increasing stomatal conductance, relative leaf moisture, and catalase enzyme and leaf soluble protein. In general, seed pretreatment as well as seedling foliar application with 0.375 mM melatonin had the greatest effect on drought stress modulation.

The results showed that concentrations of 1.5 spermidine and 0.375 mM melatonin had the highest percentage and germination rate. In the greenhouse, experimental treatments showed a significant effect on increasing stomatal conductance, relative leaf moisture, and catalase enzyme and leaf soluble protein. In general, seed pretreatment as well as seedling foliar application with 0.375 mM melatonin had the greatest effect on drought stress modulation.