واکنش های فیزیولوژیکی و بیوشیمیایی توت‌فرنگی تحت تاثیر عصاره جلبک دریایی در شرایط کمبود آهن

استفاده از زیست محرک‌ها در کشاورزی ارگانیک و پایدار با هدف کاهش مصرف کودهای شیمیایی همواره مورد توجه قرار گرفته است. هدف از این مطالعه بررسی امکان جایگزینی کلات آهن در محلول غذایی با نوعی زیست محرک طبیعی محتوی عصاره جلبک دریایی به نام اکتیویو در کشت توت‌فرنگی ارقام کاماروسا و سلوا در سیستم کشت بدون خاک بود. آزمایش به‌صورت فاکتوریل در قالب طرح کاملاً تصادفی شامل تیمارهای شاهد (محلول غذایی حاوی کلات آهن با 6=ph)، محلول غذایی بدون آهن و حاوی اکتیویو با 6=ph، محلول غذایی حاوی کلات آهن با 8=phو محلول غذایی بدون آهن و حاوی اکتیویو با 8= phبود. نتایج نشان داد، عصاره جلبک دریایی روی همه صفت های اندازه‌گیری شده اثر معنی‌دار داشت، به‌طوری‌که وزن ‌تر و خشک اندام‌های هوایی، وزن تر ریشه‌ها و همچنین میزان کلروفیل و آهن فعال برگ‌ها در تیمار حاوی اکتیویو با 6= phمشابه گیاهان شاهد بود. ارزیابی فعالیت آنزیم‌های کاتالاز و پراکسیداز در برگ نیز نشان داد که کاربرد اکتیویو سبب افزایش فعالیت این آنزیم ها در گیاهان در شرایط کمبود آهن شد. بر اساس نتایج این پژوهش عصاره جلبک دریایی توانست جایگزین کلات آهن برای پرورش توت‌فرنگی در محلول غذایی شده و امکان تولید این گیاه را با کاهش استفاده از ترکیبات مصنوعی آهن فراهم کند، به عبارت دیگر کاربرد اکتیویو به جای کلات آهن در 6=ph محلول غذایی توصیه می شود.

Physiological and Biochemical Responses of Strawberries Affected by Seaweed Extract under Iron Deficiency Conditions

Introduction: Nowadays, crop production methods are moving towards organic farming through reducing the use of chemicals in agriculture. The new generation of seaweed extracts, like Actiwave, could be a promising approach to achieve a part of this goal. Actiwave is a metabolic enhancer derived from a type of brown algae, called Ascophyllum nodosum, and contains compounds that play an important role in plant metabolism. The application of this product on various plants has often improved their vegetative and reproductive characteristics. One of the important problems in our agricultural lands is the presence of bicarbonate ion in soil (calcareous soils) or irrigation water, which increases pH around plant’s root followed by chlorosis between the veins in the young leaves resulting in a reduction or halt in plant growth. The induction of chlorosis in calcareous soils is attributed to iron deficiency due to reduction of iron absorption or availability. The use of biostimulants may help to improve plant growth under such conditions. The aim of this study was to investigate the possibility of replacing iron chelates in nutrient solution with Actiwave in two optimal and alkaline pH and its effect on some of the vegetative and biochemical properties of two strawberry cultivars in a soilless system.;Materials and Methods: Strawberry seedlings of Camarosa and Salva cultivars were cultivated in pots containing cocopeat and perlite (1:1), followed by plant’s irrigation and nourishment through a plant nutritional program. The project was conducted in a factorial experiment (with two factors) based on a completely randomized design with three replications. The first factor was strawberry cultivar in two levels including Camarosa and Salva, and the second factor was iron treatment in four levels consisting of Hoagland nutrient solution containing iron chelate (pH=6), ironfree nutrient solution containing 0.25 ml/l Actiwave (pH=6), Hoagland nutrient solution containing iron chelate (pH=8), and ironfree nutrient solution containing 0.25 ml/l Actiwave (pH=8). Plants were fed for two months, at the end of which, the roots and shoot’s fresh and dry weight, chlorophylls a, b and total as well as carotenoids contents, catalase and ascorbate peroxidase activities in fresh leaf samples and also total Fe and active Fe in dried leaf and root samples were measured.;Results and Discussion: The results showed that the algae extract had a significant effect on all the measured parameters, so that fresh and dry weights of the aerial parts, fresh weight of the roots, as well as chlorophyll and active iron content of leaves in the treatment containing Actiwave with pH=6 was similar to the control plants. Evaluation of the activity of catalase and peroxidase enzymes in the leaf also showed that Actiwave application reduced iron deficiency stress in plants increasing the activity of these enzymes under such conditions. The reason behind these effects can be due to the Actiwave ingredient content, which includes betaine, alginates and kahydrin (derived from vitamin K). Since betaines have cytokine activity, they can increase root growth by increasing the amount of cell division. Increasing the chlorophyll content, which can be the result of reduced chlorophyll degradation, is probably due to the presence of betaines in the seaweed extract. In addition, the presence of kahydrin and alginic acid in Actiwave, with the acidification of the rhizosphere, stimulated the release of more ions around the roots, resulting in more ions received by the plant and increased their assimilation. As observed in this study, It has been proven that iron concentration in the leaf is not always an appropriate indicator for checking the state of iron in plants. Some studies attribute this to limiting the growth of young leaves and the accumulation of iron in tissues or inactivation of iron in tissues occurred through the process of alkalization in leaf apoplast. It is found that activity of catalase and ascorbate peroxidase containing iron and the iron extracted with hydrochloric acid are the most effective indices for checking the iron status in plants, and the concentration of the total iron is less important in this regard. According to the results of this study, algae extract was able to replace iron chelate in nutrient solution for growing strawberry, and so made it possible to produce this fruit by reducing the use of synthetic iron compounds. In other words, application of Actiwave instead of iron chelate is recommended in nutrient solution with pH=6.