Melatonin applied to cucumber (Cucumis sativus L.) seeds improves germination during chilling stress

Abstract

The relationship between germination and melatonin applied during osmo- and hydropriming was studied in cucumber seeds. The proportion of nuclei with different DNA contents, the mean ploidy and the (2C + 4C = 8C)/2C ratio in unprimed and primed, dry and imbibed at 10 degrees C seeds were established by flow cytometry. Thiobarbituric acid reactive substances and protein oxidation were also estimated. Melatonin and indole-3-acetic acid (IAA) concentrations in the seeds were determined using high-performance liquid chromatography with electrochemical detection. Being sensitive to chilling stress, seeds that germinated well (99%) at 25 degrees C showed only 30% germination at 15 degrees C, and almost no germination (4%) at 10 degrees C. Hydropriming in water improved seed germination to 50-60% at 15 degrees C and the addition of melatonin (25-100 M) also increased the rate of germination. Osmopriming in polyethylene glycol increased germination at 15 degrees C to 78%, and 98% when combined with 50 M melatonin. Osmoprimed seeds germinated even at 10 degrees C and reached 43%, and 83% when 50 M melatonin was applied. None of the treatments induced DNA synthesis, although during the first 24 hr of imbibition at 10 degrees C the mean ploidy and the (2C + 4C = 8C)/2C ratio increased, which is indicative of the advanced Phase II of germination. Hydro- and osmopriming slightly decreased IAA content in the seeds in most of the cases; only hydropriming with 100 and 500 M melatonin increased it. Melatonin protected membrane structure against peroxidation during chilling, but excessive melatonin levels in cucumber seeds (approximately 4 microg/g fresh weight) provoked oxidative changes in proteins. There is still lack of information explained clearly the role of melatonin in plant physiology. This molecule acts multidirectionally and usually is alliged to other compounds.

Physiological response of plants to polyethylene glycol (PEG-6000) by exogenous melatonin application in wheat

“…In our study, IAA would take central effect for HG35, but ABA would take central effect for JM22 during drought regulation process due to different drought tolerances. Melatonin concentrations applied exert contrasting roles such as stimulatory effect or inhibitory one in different organs and wheat cultivars (Chen et al, 2009;Posmyk et al, 2009). In the present experiment, our results on different melatonin concentrations were also shown to be consistent with previous reports.…”

“…Fresh leaf and root samples (0.5 g) were measured based on the description of Prochazkova et al (2001). Samples were homogenised in precool acetone (1:1) with a little quartz sand.…”

Influence of abiotic stress signals on secondary metabolites in plants

“…Moreover, Melatonin applied to cucumber (Cucumis sativus L.) seeds improves germination during chilling stress. 56 Recently, Zhao et al 57 reported that melatonin improves the survival of cryopreserved callus of Rhodiola crenulata. The survival rate of the cryopreserved callus increased when the callus was pretreated with 0.1 μM melatonin.…”

Involvement of melatonin applied to Vigna radiata L. seeds in plant response to chilling stress

“…Many researchers have described the protective role of MEL against environmental stresses, such as heavy metals [4,8], cold [9,10], UV-B radiation [11] or salt stress [12]. Antioxidant activity of MEL seems to participate in: (i) the direct scavenging of free radicals, (ii) stimulation of antioxidant enzymes, (iii) augmentation of the activities of other antioxidants, (iv) protection of antioxidant enzymes against oxidative damage, or (v) an increase in the efficiency of the mitochondrial electron transport chain, thereby lowering electron leakage and the generation of free radicals [6].…”