بررسی پاسخ‌های مورفوفیزیولوژیک توده‌های بومی علف گندمی تاجدار (Agropyron Cristatum L.) در شرایط تنش خشکی و شوری

خشکی و شوری از جمله تنش‌های غیرزنده مضر برای رشد چمن در طیف گسترده‌ای از جهان می‌باشند. هدف از اجرای این آزمایش، انتخاب توده‌های مقاوم به خشکی و شوری چمن جهت استفاده در برنامه مدیریت چمن در شرایط تنش خشکی و شوری بود. آزمایش به‌صورت کرت‌های خردشده بر پایه طرح کاملاً تصادفی با سه تکرار انجام شد. عوامل آزمایش شامل سه تیمار آبیاری بود که به مدت 45 روز اعمال گردید: 1) گیاهان شاهد (بدون تنش)، 2) تنش خشکی (قطع آبیاری به مدت 45 روز) 3) تنش شوری (روزانه 100 میلی‌لیتر با شوری 9 دسی‌زیمنس بر متر). تیمارهای آبیاری به‌عنوان فاکتور اصلی در سه سطح (شاهد، تنش خشکی و تنش شوری) و توده‌های علف گندمی در شش سطح به‌عنوان کرت فرعی در نظر گرفته شدند. نتایج حاصل از این تحقیق نشان داد تنش خشکی و شوری باعث کاهش کیفیت در توده‌های علف گندمی تاجدار شدند و سطح کاهش کیفیت بین توده‌ها متفاوت بود. نتایج ما نشان داد، توده سبزوار تحت تنش خشکی و شوری به ترتیب، بالاترین ارتفاع (5.52 و 5.86 سانتی‌متر) و بیشترین محتوی کلروفیل (2.85 و 2.75 میلی‌گرم برگرم وزن‌تر) را نشان می‌دهد. نتایج به‌دست‌آمده از بررسی کربوهیدرات‌های محلول اندام هوایی، محتوی آب نسبی و میزان نشت الکترولیت نشان داد که در گیاهان تحت تنش خشکی توده‌های دماوند و سبزوار بیشترین مقدار کربوهیدرات‌های محلول (332.16 و 345.14 میلی‌گرم برگرم وزن خشک)، بیشترین محتوی آب نسبی (59.18 و 62.18 درصد) و کمترین میزان نشت الکترولیت (48.16 و 59.14 درصد) را به خود اختصاص دادند. در شرایط تنش شوری، توده دماوند (322.15 میلی‌گرم برگرم وزن خشک) بیشترین کربوهیدرات محلول، توده سبزوار (68.42 درصد) و اراک (65.14 درصد) بیشترین محتوی آب نسبی و توده سبزوار (54.17 درصد) کمترین میزان نشت الکترولیت را نشان دادند. مطابق نتایج این آزمایش رتبه‌بندی مقاومت به تنش خشکی به صورت سبزوار >دماوند > اراک > ارومیه = تاکستان > هشتگرد و رتبه‌بندی مقاومت به شوری به‌صورت سبزوار >اراک > دماوند > هشتگرد = تاکستان > ارومیه می‌باشد. توده‌های سبزوار و دماوند مقاومت خوبی نسبت به خشکی، و توده‌های سبزوار و اراک مقاومت خوبی نسبت به تنش شوری در مقایسه با سایر توده‌های علف گندمی تاجدار از خود نشان دادند.

Study of Morphophysiological Responses of Iranian Crested Wheatgrass Genotypes (Agropyron cristatum L.) under Drought and Salinity Stresses

Introduction: Drought and salinity are the most detrimental abiotic stresses for turfgrass growth across a wide range of geographic locations. Most cool season grass species are not well adapted to extended periods of drought and salinity stress. The decline in turf quality caused by drought and salinity stresses is a major concern in turfgrass cultivation and management. Therefore, developing management practices for improving drought and salinity resistance of turfgrasses has become imperative in arid and semiarid regions. Grass genotypes differ in their responses to drought and salinity stresses, which involve changes in morphological and physiological aspects. Understanding of relative involvement of each morphological and physiological characteristic in drought and salinity tolerance is important in selecting grass genotypes to facilitate breeding of drought and salinitytolerant genotypes. The purposes of this research were to make selections of genotypes tolerant to drought and salinity stress for turfgrass management program.; Materials and Methods: To study some morphological and physiological responses of six Iranian crested wheatgrasses (Agropyron cristatum L.) under drought and salinity, an experiment was conducted in the greenhouse of College of Abureyhan, University of Tehran, Iran. Six Iranian Agropyron cristatum genotypes were collected from six locations in Iran. Agropyron cristatum genotypes were planted in polyvinyl chloride tubes and kept in the greenhouse. Pots were filled with sandy loam soil which had been sterilized in an oven at 160ºC for 6 h. Irrigation was applied as needed to prevent any visible stress during grass establishment. Grasses were watered three times weekly to maintain plants under wellwatered conditions and soil moisture at field capacity. The experiment consisted of three treatments: 1) wellwatered plants were irrigated three times per week with distilled water (control), 2) Drought stress was imposed by withholding irrigation for 45 days (drought stress), and 3) plants were irrigated daily with 100 mL of 9 dS.m–1 NaCl solution (salinity stress). To avoid primary salinity shock, the soil in each pot was drenched with 100 mL NaCl solution at incremental electrical conductivity (EC) by 3 dS.m–1 per day until the final EC reached 9 dS.m–1. Data were subjected to analysis based on a splitplot design with water treatments as mainplots and genotypes as subplots. Irrigation treatment as the main factor in three levels (control, drought, and salinity) and crested wheatgrass at six levels were considered as subplots. Studied characteristics such as height, turf quality, chlorophyll content, soluble carbohydrates, relative water content, electrolyte leakage, root penetration, and effective root depth were recorded. Statistical significance was tested using the analysis of variance procedure in SAS 9.1 (SAS Institute Inc., Cary, NC). Differences between the means were determined using the Fisher’s protected LSD test at the 5% probability level.;Results and Discussion: The results of this study showed that drought and salinity stress decreased the quality of crested wheatgrass masses, and reduced the level of quality varied among the masses. Throughout the experiment, ‘Sabzevar’ and ‘Damavand’ under drought conditions and ‘Sabzevar’, ‘Arak’ and ‘Damavand’ under salinity conditions maintained higher Turf quality compared with other genotypes. Total chlorophyll content of ‘Sabzevar’ and ‘Damavand’ were higher than other genotypes under drought and salinity conditions. The maintenance of higher chlorophyll content has been associated with better drought and salinity tolerance in plant. The soluble sugar content of ‘Sabzevar’ and ‘Damavand’ under drought conditions and ‘Sabzevar’, ‘Arak’ and ‘Damavand’ under salinity conditions were higher than other genotypes during the experiment. Soluble sugar content is an important compatible osmolyte in plants. Increased accumulation of soluble sugar content in stressed plants may be an adaptation process and resistance strategy to abiotic stresses in plants. Throughout the experiment, ‘AEKQI’, ‘Sabzevar’ and ‘Damavand’ genotypes under drought conditions and ‘Sabzevar’ genotypes under salinity conditions maintained higher relative water content in compared with other genotypes. Higher RWC indicates the ability of the leaf to maintain its higher water content under stress conditions with the simultaneous capability of the root system to take up adequate water. Based on morphological and physiological analysis for drought and salinity tolerance in investigated genotypes, the tolerance ranking would appear to be ‘Sabzevar’ > ‘Damavand’ > ‘Arak’ > ‘Urmia’ = Takestan > ‘Hashtgerd’ under drought stress and ‘Sabzevar’ > ‘Arak’ > ‘Damavand’ > ‘Takestan’ = ‘Hashtgerd’ > ‘Urmia’ under salinity stress. The results of this study showed that ‘Sabzevar’ and ‘Damavand’ genotypes had good tolerance to drought stress, and ‘Sabzevar’ and ‘Arak’ genotypes had good tolerance to salt stress than other Iranian crested wheatgrass genotypes.