اثر پیش‌تیمار ملاتونین در بهبود برخی صفات رویشی و فیزیولوژیک گیاه همیشه بهار (.calendula officinalis l) تحت آبیاری با آب شور

ملاتونین به‌عنوان یک آنتی‌اکسیدان قوی معرفی شده است که در شرایط تنش، نقش حفاظتی داشته و در هنگام مواجهه با تنش‌های مختلف از جمله شوری به‌عنوان یک تنظیم‌کننده اسمزی و اصلاح‌کننده متابولیکی عمل می‌کند. به‌منظور بررسی اثر پیش‌تیمار ملاتونین بر بهبود صات مورفوفیزیولوژیک گیاه همیشه بهار (.calendula officinalis l) آزمایشی به‌صورت فاکتوریل در قالب طرح کاملاً تصادفی با سه تکرار انجام شد. ملاتونین در سه سطح (صفر، 100 و 150 میکرومولار) و شوری با کلرید سدیم در چهار سطح (صفر، 30، 60 و 90 میلی‌مولار) به‌ترتیب به‌عنوان تیمارهای اول و دوم در نظر گرفته شدند. براساس نتایج به‌دست آمده بیش‌ترین ارتفاع گیاه، بیش‌ترین تعداد برگ و بلندترین طول ریشه در تیمار ملاتونین 150 میکرومولار بدون شوری به‌دست آمد. در مقابل در شوری 90 میلی‌مولار و بدون حضور ملاتونین کم‌ترین تعداد برگ و ارتفاع مشاهده شد. وزن تازه ریشه در سطوح مختلف شوری همگام با افزایش غلظت شوری روند کاهشی نشان داد به طوری‌که کم‌ترین وزن تازه ریشه در غلظت 90 میلی‌مولار نمک بدون ملاتونین مشاهده شد. همچنین وزن تازه ریشه همراه با افزایش غلظت ملاتونین به‌کار برده شده افزایش داشت. بیش‌ترین محتوای آب نسبی و درصد پتاسیم برگ در تیمار ملاتونین 150 میکرومولار مشاهده شد و با افزایش غلظت نمک، محتوای آب نسبی و غلظت یون پتاسیم برگ کاهش یافت. بیش‌ترین میزان قند محلول در شوری 60 میلی‌مولار به‌علاوه تیمار ملاتونین 100 میکرومولار و بیش‌ترین مقدار پرولین در تیمار شوری 60 میلی‌مولار به‌علاوه تیمار ملاتونین 150 میکرومولار ایجاد شد. با توجه به نتایج به‌دست آمده، پیش‌‌تیمار ملاتونین در بهبود صفات رویشی و فیزیولوژیک همیشه بهار تحت تنش شوری موثر واقع شد به‌گونه‌ای که توانست اثر شوری به‌ویژه در غلظت‌های 30 و 60 میلی‌مولار کلرید سدیم را کاهش دهد.

effect of melatonin pretreatment on improving some vegetative and physiological traits of marigold (calendula officinalis l.) under saline water irrigation

abstractmelatonin has been introduced as a strong antioxidant that has a protective role in stressful conditions and acts as an osmotic regulator and metabolic modifier when different stresses occur. in order to investigate the effect of melatonin pretreatment on improving the morphophysiological traits of calendula officinalis l., a factorial completely randomized design with three replications was conducted. melatonin at three levels (0, 100 and 150 µm) and sodium chloride at four levels (0, 30, 60 and 90 mm) were considered as the treatments. based on the obtained results, the highest plant height, the highest number of leaves and the longest root length were obtained in 150 μm melatonin without sodium chloride treatment. on the other hand, at 90 mm salinity and without the presence of melatonin, the lowest number of leaves and plant height were observed. the fresh weight of the root, at different levels of salinity, showed a decreasing trend with increasing salinity concentration, so that its lowest value was observed in the concentration of 90 mm salt without melatonin. the fresh weight of the root increased with the increase in melatonin concentration. the highest relative water content and potassium percentage of leaves were observed in 150 μm melatonin treatment. as the salt concentration increased, the relative water content and potassium concentration decreased. the highest amount of soluble sugar related to 60 mm salinity in combination with 100 µm melatonin and the highest amount of proline was observed in 60 mm salinity + 150 µm melatonin. the results indicated that melatonin pretreatment was effective on the vegetative and physiological traits of marigold under salinity stress and was able to reduce the effect of salinity, especially in the concentrations of 30 and 60 mm sodium chloride.background and objectives: high nacl levels, due to osmosis and ionization, can significantly diminish plant height, leaf area, and the fresh and dry weights of shoots and roots. melatonin, a ubiquitous molecule produced in plants, acts as a growth regulator similar to indole acetic acid (iaa), which promotes cell expansion and growth. under nacl stress, plants close the stomata to prevent water loss, and this can result in decreased stomatal conductance and photosynthesis activity. however, it has been shown that the application of melatonin makes the stressful conditions tolerable for plants and leads to the opening of stomata, which has been reported to improve the photosynthetic machinery in sunflower and citrus plants (brugnoli and lauteri, 1991; meloni et al., 2003; ye et al., 2016). the aim of the present study was to investigate the role of melatonin in marigold, in order to improve vegetative and physiological traits.methods: a factorial experiment in a completely randomized design with two factors and three replications was conducted in greenhouse conditions at sari agricultural sciences and natural resources university. melatonin at three levels (0, 100 and 150 µm) and salinity at four levels (0, 30, 60 and 90 mm) were considered as the first and second factors, respectively. marigold seedlings were sprayed three times every ten days. one week after the last melatonin treatment, irrigation with sodium chloride was applied every 7 days for 35 days. one week after the last application of sodium chloride, some traits such as plant height, number of leaves, flower diameter, root length, root fresh and dry weights, leaf relative water content, soluble sugar, proline, ion leakage, and sodium and potassium contents were measured.results: the interaction between salinity and melatonin affected the plant height, number of leaves, and root length, volume and dry weight. the highest plant height (i.e., 17 cm), the number of leaves (i.e., 34) and the root length (i.e., 18.83 cm) were obtained in the 150 μm melatonin treatment without salt. the highest root volume and dry weight were observed in 100 μm melatonin treatment without salt. the highest leaf relative water content and potassium content were obtained in 150 μm melatonin treatment. the highest amounts of soluble sugar and proline were recorded in 60 mm sodium chloride + 100 μm melatonin, and 60 mm sodium chloride + 150 μm melatonin, respectively. at 30 mm salinity without the use of melatonin, the lowest proline was recorded. the highest sodium content was recorded at 60 mm sodium chloride. at the concentration of 150 μm melatonin, the sodium content in the leaf decreased. with the increase of salt concentration, ion leakage increased and it was the highest at 90 mm salinity. at the concentration of 150 μm melatonin compared to the control, a decrease in ion leakage was observed.conclusions: the results showed that salinity stress reduced the vegetative traits of marigold, but the use of melatonin reduced the damage under salinity stress conditions. melatonin, by protecting the membrane and structure of plant cells, maintaining the antioxidant system and helping to absorb potassium and reducing sodium absorption, could increase the resistance of marigold against salt stress. as a result, the use of melatonin moderated the effects of salinity and improved plant growth in saline conditions. therefore, it is recommended to use 100 and 150 μm concentrations of melatonin for improving vegetative and physiological characteristics of marigold under salinity stress conditions.references:1. brugnoli, e., lauteri, m., 1991. effects of salinity on stomatal conductance, photosynthetic capacity, and carbon isotope discrimination of salt-tolerant (gossypium hirsutum l.) and salt-sensitive (phaseolus vulgaris l.) c3 non-halophytes. plant physiol. 95(2), 628–635.  https://doi.org/10.1104/pp.95.2.628.2. meloni, d.a., oliva, m.a., martinez, c.a., cambraia, j., 2003. photosynthesis and activity of superoxide dismutase, peroxidase and glutathione reductase in cotton under salt stress. environ. exp. bot. 49(1) 69–76. https://doi.org/10.1016/s0098-8472(02)00058-8.3. ye, j., wang, s., deng, x., yin, l., xiong, b., wang, x., 2016. melatonin increased maize (zea mays l.) seedling drought tolerance by alleviating drought-induced photosynthetic inhibition and oxidative damage. acta phys. planta. 38(2), 48. https://doi.org/10.1007/s11738-015-2045-y.