استفاده از عصاره جلبک دریایی (ascophyllum nodosum) در بهبود اثرات منفی ناشی از تنش کم‌آبی در گیاه نخود با تاکید بر شاخص‌های مورفوفیزیولوژیک

این پژوهش با هدف بررسی تاثیر عصاره جلبک دریایی آسکوفیلوم بر شاخص های مورفوفیزیولوژیک گیاه نخود (رقم عادل) تحت تنش کمبود آب به صورت فاکتوریل در قالب طرح کاملاً تصادفی با سه تکرار در دانشگاه صنعتی خاتم‌الانبیاء بهبهان در سال 1395 انجام شد. تیمارهای آزمایش شامل چهار سطح محلول‌پاشی عصاره جلبک دریایی (صفر، 1.5، 2.5 و 3.5 درصد حجمی) و سه سطح تنش کم آبی شامل بدون تنش، تنش ملایم و تنش شدید (به ترتیب آبیاری در سطح 75، 50 و 25 درصد ظرفیت زراعی) بود. نتایج نشان داد که در شرایط بدون تنش سطوح 2.5 و 3.5درصد حجمی عصاره به صورت معنی داری شاخه جانبی، تعداد غلاف در بوته، وزن خشک اندام هوایی، طول ریشه، محتوای آب نسبی، محتوای کلروفیل a، b و کلروفیل کل را در مقایسه با شاهد افزایش داد. در شرایط تنش ملایم، کاربرد سطح 2.5 درصد عصاره جلبکی موجب افزایش معنی دار تعداد شاخه جانبی (33%+)، تعداد غلاف (22%+)، وزن خشک اندام هوایی (19%+)، طول ریشه (12%+)، محتوای آب نسبی (7%+)، محتوای کلروفیل a (12%+)، b (10.5%+) و کلروفیل کل (11%+) در مقایسه با شاهد شد. در شرایط تنش شدید، محلول‌پاشی 2.5 درصد حجمی توانست تعداد شاخه جانبی (30%+)، تعداد غلاف در بوته (27%+)، محتوای آب نسبی (6%+) و محتوای کلروفیل b (10%+) را در مقایسه با سطح شاهد بهبود دهد. با توجه به نتایج این مطالعه، استفاده از عصاره جلبک آسکوفیلوم نودوسوم در تمامی سطوح مورد بررسی در شرایط بدون تنش برای گیاه نخود پیشنهاد می گردد، اما در شرایط تنش ملایم و شدید سطح 2.5 درصد حجمی برای بهبود خصوصیات مورفوفیزیولوژیک توصیه می گردد.

Use of seaweed )Ascophyllum nodosum) extract in mitigating the negative effects of water deficit stress in chickpea by evaluating morphophysiological indicators

IntroductionSeaweed (Ascophyllum nodosum) extract can play an effective role in plant growth and development due to having plenty of nutrients, plant growth regulators and helpful microorganisms can improve soil physicochemical characteristics. Seaweed extract is rich in growth hormones such as auxin, cytokinin, nutrients and widely used elements such as nitrogen, potassium, calcium, magnesium, trace elements such as iron, zinc, copper, manganese and other valuable compounds such as mineral salts, vitamins and Antioxidants have a positive and significant effect on morphophysiological and functional characteristics of plants. In this regard, several studies have reported that the use of seaweed extract as a foliar application can increase the morphophysiological characteristics of crops. Water deficit stress is one of the most important factors limiting plant yield, the use of remedial treatments to reduce the negative effects of stress is essential and increases the strength and resistance of plants to abiotic stresses. The main purpose of this study was the effect of foliar application of Ascophilum nodosum seaweed extract in reducing the negative effects of water deficit stress on chickpea (Adel cultivar). Materials and MethodsIn order to evaluate the effects of seaweed extract on morphophysiological indices of chickpea (Adel cultivar) under water deficit stress, a factorial experiment based on completely randomized design was conducted in natural environment and with three replications at the Khatam Alanbia University of Behbahan. The experiment treatments consisted of four levels of seaweed extract (0, 1.5, 2.5 and 3.5%) and three levels of water deficit stress: nonstress, moderate stress and severe stress (irrigation at 25, 50 and 75 of field capacity, respectively). In this study, morphological and physiological traits such as plant height, number of leaves per plant, number of lateral branches, number of pods per plant, shoot dry weight, root dry weight, root length, photosynthetic pigments (chlorophyll a, chlorophyll b, carotenoids and Total chlorophyll), net photosynthesis, cell membrane stability and relative water content were measured. At the end of the growth period (about 50 days after planting), the aerial part was separated from the plant roots. In order to determine the dry weight of shoots and roots, the samples were dried in an oven at 72 °C for 48 hours and then their weight was determined with the AND scale model GT300 made in Germany with an accuracy of 0.001 g. Lichtenthaller and Wellburn (1983) method was used to measure chlorophyll and carotenoids. In order to measure the amount of netphotosynthesis, a KR8700 gas exchangemeasuring device made by Korea Tech Company was used. Bian and Jiang, (2008) method was used to measure the relative water content of leaves. Results and DiscussionThe results on the simple effects of seaweed extract showed that all foliar application levels led to a significant increase in plant height, leaf number, root dry weight, netphotosynthesis rate, cell membrane stability and carotenoids content compared to the control. Seaweed extract of 2.5 and 3.5% levels led to a significant increase in root dry weight, number of leaves per plant, plant height and cell membrane stability compared to the control. Foliar application of 2.5% compared to other levels resulted in a significant increase in netphotosynthesis and carotenoids. Evaluation of simple effects of water deficit stress showed that severe stress (25% of field capacity) significantly reduced plant height, number of leaves, root dry weight, net photosynthesis, cell membrane stability and carotenoids content compared to nonstress conditions (75% of capacity) and moderate stress (50% of field capacity). The results of interaction of treatments showed that in nonstress conditions, levels of 2.5 and 3.5% of algae extract significantly increased the number of lateral branches, number of pods per plant, shoot dry weight, root length, relative water content, chlorophyll a, b and total chlorophyll content compared to the control. Under moderate stress conditions, application of 2.5% of seaweed extract significantly increased the number of lateral branches (+33%), number of pods per plant (+22%), shoot dry weight (+19%), root length (+12 %), Relative water content (+7%), chlorophyll a (+12%), chlorophyll b (+10.5%) and total chlorophyll (+11%) were compared with the control. Under severe stress conditions, 2.5% foliar application was able to increase the number of lateral branches (+30%), number of pods per plant (+27%), relative water content (+6%) and chlorophyll b content (+10%) in compare with control. ConclusionAccording to the results of this study, the use of Ascophilum nodosum seaweed extract in all studied levels is recommended for chickpea in nonstress conditions, but in moderate and severe stress levels, 2.5% is recommended to improve the morphophysiological characteristics of chickpea.