ارزیابی پاسخ‌های رشدی، عملکردی و فیزیولوژیکی خیار شاخدار آفریقایی (cucumis metuliferus l.) به تنش کم آبیاری

تنش خشکی به عنوان یک تنش غیرزیستی مهم رشد و عملکرد گیاهان را کاهش می دهد. به منظور بررسی اثر تنش کم آبیاری بر رشد، عملکرد و شاخص های فیزیولوژیکی خیار شاخدار آفریقایی، آزمایشی در قالب طرح بلوک های کامل تصادفی در سه تکرار در مزرعه پژوهشی دانشگاه زنجان در سال 1398 انجام شد. سطوح آبیاری شامل سه سطح 100، 80 و 60 درصد نیاز آبی گیاه بود. نتایج نشان داد که تنش کم آبیاری، رشد و عملکرد میوه را بطور معنی داری کاهش داد. کمترین طول بوته، تعداد میوه (10.9) و عملکرد بوته (1.6 کیلوگرم) در تیمار کم آبیاری 60 درصد حاصل شد. وزن میوه تحت تاثیر تنش کم آبیاری افزایش یافت و بیشترین وزن متوسط میوه (164.05 گرم) در تیمار کم آبیاری 80 درصد حاصل شد. کیفیت میوه به طور معنی داری تحت تاثیر تیمار آبیاری قرار گرفت. سفتی بافت میوه و مقدار ویتامین ث تحت تنش کم آبیاری کاهش یافت و مواد جامد محلول کل، مقدار فنل کل و ظرفیت آنتی اکسیدانی میوه افزایش یافت به طوری که بیشترین مقدار مواد جامد محلول (4.43 درصد بریکس)، فنل (7.6 میلی گرم بر گرم وزن تر) و ظرفیت آنتی اکسیدانی (48.78 درصد) و حداقل مقدار ویتامین ث (10.02 میلی گرم بر 100 میلی لیتر) و سفتی بافت میوه (2.73 کیلوگرم بر سانتی متر مربع) در تیمار کم آبیاری 60 درصد مشاهده شد. با افزایش تنش کم آبیاری، محتوای نسبی آب برگ و محتوای کلروفیل، غلظت عناصر فسفر و پتاسیم برگ کاهش یافت. درصد نشت یونی، محتوای کاروتنوئید و تجمع پرولین در پاسخ به افزایش تنش کم آبیاری به طور معنی داری افزایش یافت. در تیمار کم آبیاری 80 درصد، اگرچه عملکرد میوه 13.9 درصد کاهش یافت ولی در مصرف آب 20 درصد صرفه جویی شد و با افزایش مواد جامد محلول و ظرفیت آنتی اکسیدانی، کیفیت میوه و اندازه میوه بهبود یافت.

the evaluation of growth, yield and physiological responses of african horned cucumber (cucumis metuliferus l.) to deficit irrigation

introduction water stress is the most prominent abiotic stress limiting agricultural crop growth and productivity. deficit irrigation stress as a consequence of the progressive decrease in water availability has been a hot topic regarding food security during the last two decades. growth and development of plants is influenced by reduction in turgor that results in decreased nutrient acquisition from dry soil. when water supply is limited, plant growth and yield is reduced and plant structure is modified by decreasing in leaf size. the effect of deficit irrigation on fruit yield and quality has been reported by numerous researchers with different results. in melon, deficit irrigation reduced marketable fruit number and yield, average fruit weight, fruit diameter and did not affect rind thickness and seed cavity, but increased total soluble solids content. although the effects of water stress have been studied on growth and yield of different crops during the last years, recent information on the response of african horned cucumber yield and quality to deficit irrigation remains limited, particularly about the results of restricted water distributions in arid and sub-arid environments. the main goal of this study was to evaluate the effect of controlled deficit irrigation on growth, physiological parameters and yield and fruit quality of african horned cucumber.material and methods field experiment was performed based on a completely randomized block design with three irrigation regimes (60, 80 and 100 %etc), whit three replications at research farm of university of zanjan during the 2019. the african horned cucumber seeds were sown on 1th july 2020 at recommended spacing of 50 cm in row with 120 cm between rows. the irrigation system consisted of one drip line every crop row. the three irrigation levels were calculated based on actual evapotranspiration (etc): (1) control, irrigated 100% crop water requirement, (2) deficit irrigation 80% etc and (3) deficit irrigation 60% etc. the water requirement of the plant for control treatment was estimated using long-term average daily data of meteorological parameters recorded at zanjan meteorological station and following relation. before starting the differential irrigation at five-leaf stage, all treatments were supplied with similar amount of water to maximize stands and uniform crop establishment. during plant growth, the relative water content, proline content, electrolyte leakage, chlorophyll and carotenoids, p and k contents were measured. after fruit harvest, vine length of each plant, leaf dry weight and stem diameter were measured. the fruits were harvested when color changed from green to yellow. fruit weight, fruit number per plant and fruit yield per plant was measured. immediately after harvest, fruit firmness, total soluble solid, total phenols content, antioxidant capacity and vitamin c were determined. results and discussion as the results showed water deficit stress significantly reduced plant length, chlorophyll content, and increased carotenoids content. based on the findings, deficit irrigation caused a significant reduction in leaf relative water content. according to the results, phosphorus and potassium contents in african horned cucumber leaves decreased with deficit irrigation treatments. the highest p and k contents were found under irrigation 100 %etc treatment. drought stress and associated reduction in soil moisture can decrease plant nutrient uptake by reducing nutrient supply through mineralization. the proline content increased with the deficit irrigation treatments; in particular with sever deficit irrigation (60 %etc). mean comparisons of data showed that deficit irrigation led to a significant increase in electrolyte leakage compared to control.water deficit stress caused significant reductions in yield.