اثرات تنظیم کننده های رشد و اسید آمینه پرولین بر عملکرد و اجزاء عملکرد گیاه ذرت سینگل کراس 704 در شرایط تنش خشکی در استان اصفهان

ابداع و استفاده از روش‌هایی که موجب افزایش مقاومت محصول در شرایط تنش خشکی می‌گردد، حائز اهمیت فراوان است. به‌منظور بررسی اثر محلول‌پاشی تنظیم‌کننده‌های رشد و اسیدآمینه پرولین بر عملکرد و اجزاء عملکرد و بیان ژن rab-17 (از گروه2 lea)، در ذرت سینگل کراس 704، آزمایشی به‌صورت اسپلیت‌پلات در قالب طرح بلوک‌های کامل تصادفی با سه تکرار در سال‌های 1394 و 1395 در مزرعه تحقیقاتی دانشگاه آزاد اسلامی واحد خوراسگان (اصفهان) اجرا گردید. سه تیمار آبیاری پس از 70 (شاهد)، 90 و 100 میلی‌متر تبخیر از سطح تشت تبخیر استاندارد کلاس a به‌عنوان عامل اصلی و محلول‌پاشی 5 تیمار بنزیل آدنین (ba6) جیبرلیک اسید (ga(3+7، پرولین، (ba6+ga(3+7+ پرولین و محلول‌پاشی آب خالص به‌عنوان عامل فرعی در نظر گرفته شدند. عملکرد علوفه و بلال، میزان پرولین، شاخص سطح برگ، محتوای رطوبت نسبی و میزان بیان ژن rab-17 به‌عنوان یک ژن القا شونده در شرایط تنش خشکی بررسی گردید. بر اساس نتایج تجزیه واریانس مرکب، اثر تنش خشکی و محلول‌پاشی بر عملکرد علوفه و بلال، میزان پرولین و شاخص سطح برگ معنی‌دار بود. همچنین اثر تنش خشکی بر محتوای رطوبت نسبی و بیان ژن rab-17 در سطح احتمال 1% معنی‌دار گردید. بر طبق نتایج مقایسه میانگین، تنش خشکی موجب کاهش عملکرد علوفه و بلال، شاخص سطح برگ و محتوای رطوبت نسبی و افزایش پرولین گردید. بیشترین عملکرد علوفه مربوط به شرایط تیمار شاهد بود که با تنش ملایم و شدید تفاوت معنی‌دار داشت. تیمارهای تنظیم‌کننده‌های رشد و پرولین در شرایط تنش خشکی موجب کاهش اثرات نامطلوب تنش بر عملکرد علوفه و بلال، شاخص سطح برگ و محتوای رطوبت نسبی گردیدند طبق نتایج حاصل از این پژوهش محلول‌پاشی اسیدآمینه پرولین و تنظیم‌کننده‌های رشد می‌توانند از طریق بهبود پاسخ‌های فیزیولوژیکی و ژنتیک گیاه موجب بهبود رشد و محصول ذرت در شرایط تنش خشکی شوند.

Effects of growth regulators and proline amino acid on yield and yield components of single cross 704 maize under drought stress conditions in Isfahan province

IntroductionCorn (Zea mays L) is an annual cereal crop adapted to various ecological conditions. Corn with wheat and rice are three strategic agricultural products in the world. Drought stress is the crucial factor to limit the production of corn among abiotic stresses. Drought stress in corn reduces photosynthesis, and consequently grain yield by reducing the leaf chlorophyll level. Many external and internal factors are effective in plant growth. The most important internal factors are hormones and the most important external factors are light and temperature. Hormones regulate Plant Growth Regulators (PGRs) and coordinate the processes occurring in different parts of the plant body. Plant Growth Regulators (PGRs) increase plant tolerance to various environmental stresses, such as drought, salinity, cold, and heat, and this increase in tolerance to environmental stresses depends on the production of transcripts of antistress genes, such as heat shock genes and LEA genes. It is possible to divide the products of genes induced under drought stress conditions into two categories: (1) Those playing a direct protective role against stresses; (2) Those controlling gene expression and message transmission. The Rab17 gene is one of the genes whose expression increases during drought stress following an increase in ABA. This gene belongs to second group LEA proteins. Several gene products identical to Rab17encoded proteins have been identified in different plants. Studies indicate that LEA proteins act as waterbinding molecules in grains and protect other proteins against the negative effects of drought, including ion separation from macro molecules and membrane protection against freezing damage. This study was conducted to examine the effect of the foliar application of proline amino acid and growth regulators, including benzyl adenine, gibberellic acid, as well as the combination of benzyl adenine and gibberellic acid and proline amino acid on the growth, yield and expression of the Rab17 gene in corn (Zea mays L) (Single Cross 704) under drought stress.Material and methodsThis study was conducted as a split plot on the base of randomized complete block design with three replications in 2015 and 2016. Three irrigation treatments were considered, including after 70 (control), 90, and 100 mm evaporation from the surface of standard Class A evaporation pan as the main agent. Phytohormones BA6, GA (3+ 7), proline amino acid, BA6+ GA (3+ 7) +AA and pure water as control were considered five levels of the subfactor. The plants were irrigated every 10 days before water stress was applied. Mild and severe stress treatments were applied 45 days after planting and in the 12leaf stage. Afterward, foliar Plant Growth Regulators (PGRs) and proline were applied in the stem elongation stage of corn.Results and discussionThe results and analysis of the data indicate that all the measured traits decreased with drought stress; however, the proline content increased by increasing the drought stress. For example, drought stress reduced forage yield by 46%. Corn yield was 1.3 times of the control treatment under severe drought stress with foliar application of proline amino acid. In the genetic experiments, increase of drought stress did not increase the PCR response to the Rab17 gene due to the increased secretion of abscisic acid (ABA) and susceptibility of single cross 704 to drought stress.ConclusionsAccording to the results, the foliar application of proline amino acid and Plant Growth Regulators (PGRs) can improve the growth and yield of corn under drought stress by improving plant physiological and genetic responses. Furthermore, the change in the expression of a number of genes appears to be occurred in response to drought stress. The results indicate that gene expression plays a vital role in the drought tolerance of corn; hence, it is suggested to be highly examined in further studies. It is possible that the current results draw our attention to the effects of tested Plant Growth Regulators (PGRs) on the physiology and genetic contents of corn in drought conditions to use the regulators at the right time to deal with environmental stresses in addition to perform proper management in the field, and to increase the efficiency of roots to uptake nutrients.AcknowledgmentsThe authors thank Islamic Azad University, Varamin and the Khorasgan branches, as well as Isfahan University of Technology for providing the university with necessary facilities and performing protein and genetic tests.