تاثیر اسید سالیسیلیک و اسید آبسیزیک بر شاخص‌های فیزیولوژیکی و بیوشیمیایی مرتبط با سازگاری به سرما در زیتون تلخ (.melia azedarach l

در پژوهش حاضرتحمل سرمای زمستانه درختان 5 ساله زیتون تلخ در پاسخ به کاربرد برگی اسید سالیسیلیک (sa) و اسید آبسیزیک (aba) در قالب طرح بلوک های کامل تصادفی بررسی شد. تیمارها شامل شاهد، aba 100 میکرومولار، sa 2 میلی مولار و aba100 میکرومولار + sa 2 میلی مولار بود. یک هفته پس از اعمال تیمارها، نمونه برداری از برگ ها و جوانه ها انجام شد. همچنین، تحمّل به سرمای زمستانه درختان تیمار شده و شاهد در دی و بهمن ماه بر اساس روش نشت یونی و تحت سه تیمار دمایی 6-، 12- و 18- درجه سانتی گراد ارزیابی شد. کاربرد sa + aba به ترتیب سبب افزایش 42.4، 50.3 و 21.4 درصدی محتوای فنول، پروتئین و پرولین جوانه شد. همچنین، این تیمار سبب کاهش 42.6، 36.1 و 37 درصدی نشت یونی، مالون دی آلدئید و پراکسید هیدروژن جوانه شد. در دی و بهمن ماه، کمترین میزان نشت یونی مربوط به درختان محلول پاشی شده با ترکیب هردو تنظیم کننده رشد بود. بیشترین فعالیت کاتالاز و آسکوربات پراکسیداز مربوط به تیمار aba به تنهایی بود. با این حال، بیشترین فعالیت گایاکول پراکسیداز مربوط به تیمار sa + aba و کمترین فعالیت این آنزیم ها مربوط به شاهد بود. بیشترین محتوای aba و کمترین محتوای اسید جیبرلیک درون زاد مربوط به تیمار sa + aba و کمترین محتوای این هورمون ها مربوط به شاهد بود. محتوای پوتریسین، اسپرمین و اسپرمیدین درختان تیمار شده با sa + aba به ترتیب 33.3، 16.9 و 9.37 درصد بیشتر از شاهد بود. در کل کاربرد aba و sa توانست با ایجاد تغییرات فیزیولوژیکی و بیوشیمیایی منجر به افزایش تحمّل به سرما در زیتون تلخ شود.

the effect of abscisic acid and salicylic acid on cold acclimation associated physiological and biochemical indices of chinaberry (melia azedarach l.)

in the present study, the winter cold tolerance of 5-year-old chinaberry trees was investigated in response to salicylic acid (sa) and abscisic acid (aba) under a completely randomized design. treatments included 1- control (distilled water), 2- 100 μm aba, 3- 2 mm sa, and 4- 100 μm aba + 2 mm sa combination. one week after applying the treatments, leaves and buds were sampled and also the indices related to cold tolerance were evaluated during the winter in jan. and feb. under three temperature treatments of -6 -12 and -18 ºc. the application of sa + aba increased 42.4%, 50.3% and 21.4% of bud phenol, protein and proline content, respectively. also, this treatment reduced 42.6, 36.1 and 37% of ion leakage, malondialdehyde (mda) and hydrogen peroxide (h2o2) of the buds, respectively. in january and february, the lowest ion leakage was related to trees sprayed with sa + aba. the highest activity of catalase (cat) and ascorbate peroxidase (apx) was related to aba treatment. however, the highest activity of guaiacol peroxidase (gpx) was related to sa + aba and the lowest activity of these enzymes was related to the control. the highest endogenous aba and the lowest gibberellic acid (ga3) were related to sa + aba treatment, and the lowest content of these phytohormones was related to the control trees. the content of putrecsine, spermine and spermidine of treated plants with sa + aba was 33.3, 16.9 and 9.37% higher than the control, respectively. in general, the application of aba and salicylic acid can increase the cold tolerance in chinaberry trees by creating physiological and biochemical changes. introductionchinaberry (melia azedarach l.) is a deciduous tree native to the semi-tropical areas of australia and southeast asia. however, it is planted in many cold regions of the world. for this reason, improving the tolerance to cold and freezing damages of this tree has been one of the priorities of its planting in cold regions. one of the ways to increase cold tolerance is to use growth regulators such as sa and aba. foliar application of plants with sa increases cold tolerance by reducing ion leakage and cell membrane peroxidation. aba plays an important role in cold acclimation of plants during exposure to low temperature. since the effect of these growth regulators on cold tolerance of chinaberry trees has not been reported, therefore, we investigated the effects of exogenous sa and aba on electrolyte leakage, soluble sugars, polyamines, aba, ga3, proline, total phenolic compounds, and water content in order to understand the tolerance mechanism of chinaberry trees under cold stress. additionally, the effect of exogenous application of sa and aba on cold tolerance and some physiolocical changes involved in cold acclimation was evaluated in chinaberry trees during cold acclimation stage. material and methodsin the present study, the winter cold tolerance of 5-year-old chinaberry trees was investigated in response to sa and aba application under a completely randomized design. treatments included 1- control (distilled water), 2- 100 μm aba, 3- 2 mm sa, and 4- 100 μm aba + 2 mm sa combination. one week after applying the treatments, some physiological traits including photosynthetic pigments, leaf abscission and periderm formation were recorded for each treatment group. moreover, buds were sampled and their bud water content, total phenol, total soluble protein, proline, soluble sugars (glucose, fructose and sucrose), membrane stability indices (ion leakage, mda and h2o2), phytohormones (aba and ga3), free polyamines (putrescine, spermidine and spermine) and activity of antioxidant enzymes (gpx, apx and cat) were measured in this stage (nov.). also winter cold tolerance (based on ionic leakage) of treated and control plant were evaluated in january and february under three temperature treatments of -6 -12 and -18 ºc. finally, data were analyzed with sas (9.1) software using glm program and duncan’s multiple range test (5%). results and discussionour results indicated that exogenous aba especially in combination with sa led to an array of physiological changes in chinaberry plants during cold acclimation stages. the leaf photosynthetic pigment and bud water content was decreased but shoot periderm formation and leaf abscission increased by aba + sa treatment. the application of sa + aba increased 42.4%, 50.3% and 21.4% of bud phenol, protein and proline content, respectively. biosynthesis and accumulation of osmoregulants is one of the important regulatory reactions of plants in response to environmental stresses. the highest content of soluble sugars including glucose, fructose and sucrose was related to sa + aba treated trees and the lowest was related to the control. also, this treatment reduced 42.6%, 36.1% and 37% of ion leakage, mda and h2o2 of the buds, respectively. cold stress, while increasing the peroxidation of membrane lipids and disrupting its permeability, caused the leakage of solutes and damage to the plant. the lower production of mda and h2o2 in sa + aba treated trees indicates the protective role of these hormones in membrane stability during cold acclimation period. in jan. and feb., the lowest ion leakage was related to trees sprayed with sa + aba. the highest activity of cat and apx was related to aba treatment. however, the highest activity of gpx was related to those trees treated with sa + aba and the lowest activity of these enzymes was related to the control. increased antioxidant capacity is one approach used by plants to improve their cold tolerance. metabolic changes mediated by aba and sa lead to changes in oxygen free radical levels, which in turn cause induction of the antioxidant defense system. the highest endogenous aba and the lowest ga3 were related to sa + aba treatment, and the lowest content of these phytohormones was related to the control trees. aba is an important signaling factor for low temperature stress and has a protective function for the microtubule structure of cells. the content of putrescine, spermine and spermidine of treated plants with sa + aba was 33.3, 16.9 and 9.37% higher than the control, respectively. conclusionthe use of aba, especially in combination with sa, with its effect on the physiological indices related to cold acclimation, led to a reduction in cold damage and ionic leakage of the membrane. the antioxidant properties of the treated plants were shown by increasing the activity of catalase, peroxidase and ascorbate peroxidase enzymes and increasing the accumulation of phenolic compounds. on the other hand, the application of sa + aba increase the compatible osmolytes, soluble sugars, polyamines and phytohormones (aba and ga3) increased the cold tolerance in the treated chinaberry trees compared to the control, which can be used as a method to increase winter cold tolerance in chinaberry trees in cold climate regions. acknowledgements funding of the present research was provided by malayer university of iran (grant no. 84.9–148). the authors gratefully acknowledge the malayer university.