بررسی اثر الیسیتورها بر برخی ویژگی های فیزیولوژیکی، درصد و عملکرد اسانس زوفا (.Hyssopus Officinalis L) تحت رژیم های مختلف آبیاری

به منظور بررسی تاثیر اسید سالیسیلیک و کیتوزان بر برخی خصوصیات فیزیولوژیکی و عملکرد اسانس گیاه دارویی زوفا (.hyssopus officinalis l) در شرایط تنش کم آبی، آزمایشی در مزرعه تحقیقاتی دانشگاه گنبدکاووس، به‌صورت کرت های خردشده در قالب طرح بلوک های کامل تصادفی با سه تکرار اجرا شد. فاکتورهای موردبررسی شامل دور آبیاری در سه سطح 7، 14 و 21 روزه به عنوان فاکتور اصلی و چهار سطح محلول پاشی شامل عدم مصرف الیسیتور (تیمار شاهد: محلول پاشی با آب خالص)، محلول پاشی اسید سالیسیلیک (300 میلی گرم در لیتر)، محلول پاشی کیتوزان (5 گرم در لیتر) و تلفیق اسید سالیسیلیک و کیتوزان به عنوان عامل فرعی در نظر گرفته شدند. نتایج تحقیق نشان داد اثر متقابل آبیاری و محلول پاشی بر صفات محتوای نسبی آب برگ، کمبود اشباع آب برگ و فعالیت آنزیم های آنتی اکسیدان معنی دار بود. در این پژوهش اعمال تنش کم آبی منجر به افزایش درصد اسانس گردید درحالی‌که با کاهش عملکرد اسانس همراه بود و کاربرد الیسیتورها عملکرد اسانس را افزایش داد. نتایج هم چنین مشخص کرد کاربرد کیتوزان و اسید سالیسیلیک با هم منجر به افزایش فعالیت آنزیم های آنتی‌اکسیدان تحت تیمار 14 روزه تنش کم آبی گردید. با توجه به نتایج به‌دست‌آمده و تاثیر محلول پاشی این دو الیسیتور بر ویژگی های بیوشیمیایی و متابولیتی گیاه، مصرف آن ها جهت تولید مواد باارزش دارویی ازجمله اسانس و همچنین ایجاد مقاومت به تنش خشکی توصیه می شود.

The Effect of elicitors on some physiological vharacteristics, essential oil percentage and yield in hyssop (Hyssopus officinalis L.) under different irrigation regimes

Introduction Drought stress is the most important environmental factor limiting the growth and development of plants worldwide, so drought effect is much more than other environmental stresses. The results of various studies show that drought stress will significantly reduce dry matter production of plant and some other agronomic traits such as yield and yield components. Elicitors are compounds of biological or nonbiological origin that cause biosynthesis and accumulation of secondary metabolites through induction of the Defense system. One of the newest of these compounds that can reduce the effects of drought stress is chitosan, it is a nontoxic polymer, it is degradable in nature and environmentally friendly. Salicylic acid is a natural hormonelike compound that regulates endogenous plant growth as a messenger molecule, it regulates numerous physiological processes in plants such as growth, photosynthesis, and some metabolic processes. Use of salicylic acid under drought stress enhances some physiological processes that can increase plant resistance to drought stress. The aim of this study was to evaluate the effect of using elicitors under drought stress on some physiological characteristics and yield of hyssop essential oil.   Materials and methods The study was conducted at the research farm of the Faculty of Agriculture and Natural Resources, Gonbad Kavous University, with 55° 12′ longitude and 37° 16′ north latitudes and 45 m altitude from sea in winter and spring in the crop year 20182017. GonbadKavus climate is classified as warm and semiarid by Mediterranean climate and has an average annual rainfall of 450 mm. The experiment was conducted as a factorial experiment in a randomized complete block design with three replications. The factors studied in this irrigation were three levels including 7day irrigation (I1), 14day irrigation (I2) and 21day irrigation (I3) as main factors and four levels of spraying including no use of elicitors (control treatment). Spraying solution with pure water), spraying solution of salicylic acid (300 mg/L), chitosan spraying solution (5 g/L) and combination of salicylic acid and chitosan were considered as subagents. After application of spraying treatments, to evaluate the effect of elicitors on relative leaf water content, saturation water deficiency, antioxidant enzyme activity, yield and essential oil yield samples were transferred to the laboratory.     Results and discussion The results showed that the lowest relative humidity (48.39%) and the highest saturated water deficit (51.60%) were related to severe stress conditions (21 days’ irrigation) without using elicitors that Salicylic acid increased 30.54% relative water content of plant leaves and 28.64% reduced saturated water deficit compared to nonconsumed treatments. Concerning antioxidant enzymes, the results showed that the highest amount of catalase activity was related to treatment with salicylic acid and chitosan under 14day irrigation, which resulted in a 20% increase in this enzyme. Also, the combination of two substances increased the activity of ascorbate peroxidase in control and mild (14 days) stress. Yield and essential oil percentage were not affected by interaction, but it was observed that the simple effect of spray increased this rate in this plant. Due to dry climatic conditions in the country and lack of rainfall with poor irrigation, better performance of this medicinal plant can be achieved and water loss can be prevented. Conclusion Environmental stresses are the most important factors in decreasing crop yield worldwide. Spray of salicylic acid and chitosan reduced the adverse effects of drought stress on plant and improved antioxidant activity, yield and essential oil content of hyssop.