تاثیر محلول پاشی نفتالین استیک اسید بر شاخص های فیزیولوژیکی و عملکرد میوه خیار (.cucumis sativus l) تحت شرایط کم آبیاری

به منظور ارزیابی اثر نفتالین استیک اسید بر صفات فیزیولوژیکی و عملکرد گیاه خیار (cucumis sativus l.) تحت شرایط کم آبیاری، آزمایشی به صورت کرت های خرد شده بر پایه طرح بلوک های کامل تصادفی در سه تکرار در سال 1402 اجرا شد. تیمارهای آزمایش شامل سه سطح آبیاری (100، 75 و 50 درصد نیاز آبی گیاه) به عنوان فاکتور اصلی و محلول پاشی نفتالین استیک اسید در سه سطح (صفر، 50 و 100 میلی گرم در لیتر) به عنوان فاکتور فرعی بودند. نتایج نشان داد که تنش کم آبیاری به طور معنی داری میزان کارتنوئید، پرولین، نشت یونی و فعالیت آنزیم های کاتالاز و سوپراکسید دیسموتاز را افزایش داد و محتوای کلروفیل، محتوای نسبی آب برگ و عملکرد میوه را کاهش داد. محلول پاشی نفتالین استیک اسید با افزایش محتوای کلروفیل، پرولین و فعالیت آنزیم های آنتی اکسیدانی و کاهش نشت یونی موجب بهبود عملکرد خیار گردید. باتوجه به نتایج، بیشترین محتوای کلروفیل و عملکرد (42693/7 کیلوگرم در هکتار) با کاربرد نفتالین استیک اسید 50 میلی گرم در لیتر در آبیاری 100 درصد حاصل شد. حداکثر محتوای نسبی آب برگ، حداقل نشت یونی و محتوای مالون دی آلدئید و پراکسید هیدروژن در گیاهان تیمار شده با نفتالین استیک اسید 100 میلی گرم در لیتر تحت آبیاری 100 درصد نیاز آبی بدست آمد. همچنین بیشترین فعالیت آنزیم سوپر اکسید دیسموتاز و محتوای پرولین تحت شرایط کم آبیاری 50 درصد نیاز آبی به ترتیب با کاربرد نفتالین استیک اسید 100 و 50 میلی گرم در لیتر مشاهده شد. با توجه به نتایج، کاربرد نفتالین استیک اسید 50 میلی گرم در لیتر جهت بهبود رشد و عملکرد تحت شرایط آبیاری نرمال و کم آبیاری پیشنهاد می شود.

effect of foliar application of naphthalene-acetic acid on physiological properties and yield of cucumber (cucumis sativus l.) under deficit irrigation conditions

1. introduction: cucumber (cucumis sativus l.) is one of the most important horticultural crops in the world and especially in iran. in arid and semi-arid regions، water deficit stress is a major limiting factor for crop growth and yield. increases in water scarcity with climate change reduce plant growth and development، thereby decreasing plant production in agricultural systems. due to their high leaf area/root ratio and high transpiration rate، cucumber plants are sensitive to water-deficit stress. it is well known that water deficit causes oxidative stress by increasing the production of reactive oxygen species in different cellular organelles، thus affecting membrane stability، lipid peroxidation، and other biological and physiological processes. various agricultural methods are used to increase plant resistance to environmental stresses. auxin is one of the important plant growth regulators that play multiple physiological roles in promoting cell elongation and division، seed germination، fruit development، and plant stress responses. naphthalene acetic acid (naa) has frequently been demonstrated to enhance growth parameters and productivity in vegetable and other crops. from this standpoint، this research was conducted to study the effect of foliar spraying with different concentrations of naa on the physiological properties and fruit yield of cucumber under water deficit stress. 2.      materials and methods: this experiment was conducted at the research farm of the agriculture faculty (university of zanjan، iran) in 2023 using a split plot based on a randomized complete block design with three replicates. the experimental treatments consisted of three different irrigation regimes (70، 85، and 100% etc) as the main plot and foliar spray of naa at three levels (0، 50، and 100 mg l-1) as a sub-plot. kish f1 hybrid cucumber seeds (us agriseeds company) were sown at a distance of 50 cm in rows and 120 cm between rows. different levels of naa foliar spraying started at 45th true leaf stage and were repeated two times with an interval of 15 days using a mechanical mist sprayer. irrigation was calculated based on actual evapotranspiration (etc%) rates. all necessary management practices، such as weed control، were performed according to the recommended package of practices during crop growth. during the growth period and after crop harvest، fruit yield، chlorophyll content، relative water content (rwc)، proline، phenolic compounds، electrolyte leakage، malondialdehyde (mda)، h2o2 contents، and antioxidant enzyme activity were evaluated. 3.      results and discussion: drought affects all aspects of plant physiology، including a reduction of photosynthesis rate and overproduction of reactive oxygen species، resulting in retarded plant growth and significant crop losses. the results showed that deficit irrigation significantly increased the proline content، ion leakage، catalase، and superoxide dismutase enzyme activity. in contrast، deficit irrigation reduced leaf rwc، chlorophyll content، and fruit yield. foliar application of naa improved the fruit yield with increasing chlorophyll and proline contents، leaf relative water content، and antioxidant enzyme activity، and decreasing ion leakage، mda، and h2o2 accumulation. plants have developed an antioxidant defense system that consists of enzymatic (sod، cat، pox، etc.) and non-enzymatic (ascorbate، phenolics، proline، etc.) components، which change significantly in response to different stresses، including drought. it was reported that after moderate or severe drought، proline content increased to a different extent in maize hybrids depending on their tolerance. the accumulation of proline under water deficit conditions could contribute to a plant's drought tolerance or could be a stress-injury indicator depending on plant species and the severity of the stress. according to the results، the highest chlorophyll content (2.25 mg g-1fw) and fruit yield (42693.7 kg ha-1) were obtained with the application of naa 50 mg l-1 under irrigation 100 etc%. also، the maximum rwc، and minimum ion leakage، mda، and h2o2 accumulation were obtained in the plant treated with naa 100 mg l-1 under irrigation 100 etc%. the highest value of superoxide dismutase activity (1.67 u mg-¹protein) and proline content was observed in irrigation 50 etc% with application of naa 100 and 50 mg l-1، respectively. the preliminary application of auxin compounds before drought treatment led to the adjustment of cat and pox activities، and also suggested that the auxin compounds play an essential role in balancing h2o2 levels. 4.      conclusion: according to the results of the experiment، it can be stated that the cucumber plant is a sensitive plant to water deficit stress. under water deficit، fruit yield decreased. finally، naa increased the yield by modulating the negative effects of water deficit stress in cucumber plants. therefore، according to the results، application of naa 50 mg l-1 can be proposed to improve the growth and yield of cucumber under normal and deficit irrigation conditions.