تاثیر مدت زمان تنش غرقاب در مراحل مختلف رشد بر برخی ویژگی‌های فتوسنتزی، فعالیت آنتی‌اکسیدانی و عملکرد گلرنگ زراعی (carthamus tinctorius l.)

تنش غرقاب، یک تنش محیطی پیچیده و از عوامل اصلی محدود­کننده بهره‌­وری و پایداری محصول است. به‌منظور بررسی تاثیر مدت زمان تنش غرقاب در مرحله رشد رویشی و زایشی روی برخی از ویژگی­‌های فتوسنتزی و فعالیت آنزیم‌­های آنتی­‌اکسیدان گلرنگ زراعی (carthamus tinctorius l.)، پژوهشی مزرعه‌­ای به‌صورت کرت‌های خردشده در قالب طرح پایه بلوک­‌های کامل تصادفی در سه تکرار در سال زراعی 1400-1399 در دانشگاه شهید چمران اهواز اجرا شد. سه سطح تنش غرقاب شامل: شاهد، تنش غرقاب ملایم (24 ساعت) و شدید (48 ساعت) در کرت‌های اصلی و تنش در مرحله رویشی و زایشی در کرت‌های فرعی قرار داده شدند. نتایج نشان داد که تیمارهای تنش غرقاب باعث کاهش معنی­‌دار هدایت روزنه‌­ای، سرعت فتوسنتز، شاخص کلروفیل و عملکرد دانه و روغن شد، ولی فعالیت آنزیم کاتالاز، پراکسیداز و سوپر اکسید دیسموتاز افزایش یافت. در شرایط تنش غرقاب شدید، فعالیت آنزیم­‌های آنتی‌اکسیدان در مرحله زایشی بیشتر از مرحله رویشی آن (به‌ترتیب 26، 17 و 9 درصد بیشتر) بود. بیشترین عملکرد دانه و روغن (به‌ترتیب 2056 و 469 کیلوگرم در هکتار) در شرایط آبیاری مطلوب و کمترین آن در تنش غرقاب شدید (به‌ترتیب 1256 و 317 کیلوگرم در هکتار) حاصل شد. تنش غرقاب ملایم و شدید منجر به کاهش معنی‌دار عملکرد دانه به‌ترتیب به‌میزان 34 و 39 درصد و عملکرد روغن به‌میزان 16 و 32 درصد در مقایسه با آبیاری مطلوب شد. منطبق با نتایج فعالیت آنزیم‌­های آنتی‌اکسیدان، بیشترین تاثیر تنش بر عملکرد دانه مربوط به تنش شدید در مرحله زایشی بود، به‌گونه‌­ای که سبب بیش­ترین مقدار کاهش به‌میزان 43 درصد در مقایسه با آبیاری مطلوب شد. به‌طور کلی، تنش غرقاب در مرحله زایشی گلرنگ نسبت به مرحله رویشی منجر به کاهش بیشتر عملکرد شد و این یافته‌­ها بر اهمیت تنش غرقاب بر دانه‌­های روغنی و زهکشی مزارع خوزستان در فصل زمستان جهت حذف آب اضافی پس از وقوع سیل و بارندگی­‌های سنگین تاکید دارد.

effect of waterlogging duration at different growth stages on some photosynthetic characteristics, antioxidant activity, and yield of safflower (carthamus tinctorius l.)

introductionwaterlogging is a complex environmental stress limiting crop productivity and yield stability. waterlogging in crop plants remains a serious barrier to crop production around the globe in high-rainfall areas with heavy rainfall or poor drainage. waterlogging duration and the growth stage at which it occurs can significantly influence the physiological, biochemical, and yield-related traits of safflower (carthamus tinctorius l.). however, the impact of waterlogging stress at different developmental stages on photosynthetic processes and antioxidant defense mechanisms in safflower under field conditions remains poorly understood. this study aimed to identify the most sensitive growth stage to waterlogging stress in order to enhance our understanding of the complex mechanisms underlying waterlogging tolerance in safflower.materials and methodsin order to study the influence of waterlogging duration at vegetative and reproductive stages on the yield, photosynthetic characteristics, and antioxidant activity of safflower, a field experiment was carried out during 2020-2021 growing season in a split-plot arrangement in randomized complete blocks design using three replicates per treatment. the research farm was located at shahid chamran university of ahvaz, iran. the plants were grown in the field to ensure the environmental conditions found in waterlogged and flooded soils. three waterlogging treatments were applied to plants as main plots: well-drained controls irrigated weekly, mild stress (waterlogged for 24 h) and severe stress (waterlogged for 48 h). waterlogging treatments were implemented at stem elongation (vegetative stage), and full branching (reproductive stage) as sub plots. seeds originated from the seed and plant improvement institute, karaj, iran. before and after the end of waterlogging period, waterlogging treatments were watered with sufficient water (80% field capacity) until the end of the experiment. the data for stomatal conductance, photosynthetic rate, chlorophyll index, catalase, peroxidase and superoxide dismutase enzyme activities, biological yield, oil content, and seed and oil yield was recorded. gas exchange characters were measured after waterlogging stress and then after 7 days of recovery.results and discussion the mild and severe waterlogging stress treatments at both vegetative and reproductive stages led to a significant reduction in stomatal conductance (24 and 35%, respectively), photosynthetic rate (49 and 60%, respectively), chlorophyll index (14 and 44%, respectively), biological yield (21 and 27%, respectively), seed (34 and 39%, respectively) and oil yield (16 and 32%, respectively) but increased catalase (7 and 51%, respectively), peroxidase (7 and 35%, respectively) and superoxide dismutase (9 and 17%, respectively) enzyme activities compared to well-drained controls. after 7 days of recovery, gas exchange measurements were recovered in mild and severe waterlogging stress treatments. plant growth stage and stress duration played an important role in the response to waterlogging stress. in severe stress treatment, the activity of antioxidant enzymes; catalase, peroxidase and superoxide dismutase at the reproductive stage was higher than the vegetative stage (26, 17 and 9%, respectively). however, there was no significant difference between growth stages in terms of all traits except for catalase, peroxidase and superoxide dismutase activity. the mild and severe waterlogging stress at both growth stages led to a significant reduction in seed yield by 34 and 39%, and oil yield by 16 and 32% respectively, compared to control. in contrast to the results of antioxidant enzyme activities, the maximum decrease in seed yield was found when waterlogging occurred in severe stress treatment at the reproductive stage. the reduction was 43%, when compared to the control.conclusionthe results highlighted that waterlogging during the reproductive stage of oilseed safflower resulted in higher yield loss than during the vegetative stage and these findings emphasized that the impacts of waterlogging stress on oilseed crops are important and the management practices of safflower fields especially in the khuzestan region must be strengthened during the winter season.acknowledgementwe gratefully acknowledge funding support from shahid chamran university of ahvaz grant number scu.aa99.96.