تاثیر اشعه ماورابنفش (uv-c) بر رنگیزه‌های فتوسنتزی و پارامترهای بیوشیمیایی گیاه خرفه (portulaca oleracea)

اشعه ماورا بنفش یک عامل غیرزنده مهم است که می‌تواند تولید متابولیت‌های ثانویه، از جمله ترکیبات آنتی‌اکسیدانی در گیاهان را تحریک کند. تخریب لایه ازن و پیامدهای ناشی از  آن ازجمله تابش مستقیم اشعه ماورای بنفش بر کره زمین و اثرات آن بر گیاهان زراعی و داروئی از جمله مباحثی است که مطالعات بسیار کمی روی آن صورت گرفته است. هدف از این پژوهش تاثیر اشعه ماورا بنفش در سطوح مختلف (uvc: صفر، 100، 200، 300، 400، 500، 600 و 700 نانومتر) روی فعالیت رنگیزه‌های فتوسنتزی و صفات بیوشیمیایی گیاه خرفه در قالب طرح کاملاً تصادفی با سه تکرار بررسی شد. گیاهان به مدت یک هفته، به صورت یک روز در میان و هر بار به مدت 3 دقیقه توسط دو لامپ فلورسانس با طول موج 260 نانومتر در معرض تابش فرابنفش c (در فاصله‌ی 30 سانتی‌متر از منبع نور uv با شدت 27 (وات بر متر مربع) قرار گرفتند. صفات مورد مطالعه در این پژوهش شامل کلروفیل a، کلروفیل b، کلروفیل کل، کاروتنوئید، فنل، فلاونوئید و فعالیت آنتی‌اکسیدانی بود. نتایج مقایسه میانگین نشان داد که تیمار اشعه ماورا بنفش کلروفیل a، b، کلروفیل کل، کاروتنوئید گیاه خرفه نسبت به شاهدکاهش یافت؛ اما تیمار  اشعه ماورا بنفش گیاه خرفه باعث افزایش معنی‌دار فنل، فلاونوئید و آنتی‌اکسیدان نسبت به شاهد شد. تاثیر دوزهای مختلف اشعه ماورا بنفش بر فنل و آنتی‌اکسیدان گیاه خرفه نشان داد که بیشترین و کمترین uvc به‌ترتیب در 700 و 100 نانومتر بود. به طور خلاصه، اعمال تنش نوری فرابنفش به صورت کنترل شده می‌تواند یک استراتژی جایگزین جدید برای افزایش بهره‌وری گیاه دارویی خرفه ارائه دهد. تعدیل نور uvc در سیستم‌های کشاورزی ابزاری امیدوارکننده برای افزایش تولید محصولات است.

The Effect of Ultraviolet (UV) Radiation on Photosynthetic Pigments and Biochemical Parameters of Portulaca oleracea

Introduction UVC (254280 nm) and 280320 nm) UVB, UVA (320390nm) wavelengths are irradiated with three ultraviolet strips and have detrimental effects on the growth of a number of plants. Ultraviolet light is an important nonliving factor that can stimulate the production of secondary metabolites, including antioxidant compounds in plants. Ozone depletion and its consequences, including direct UV radiation on the planet and its effects on crops and medicinal plants, are among the topics that have received very little study. Ultraviolet light in nature occurs only at low intensities, but if the inhibitory effect of the ozone layer in the stratosphere is significantly the result of nitrogen and hydrocarbon oxides the weaker the halogen, the higher its amount.Materials and Methods Portulaca oleracea seeds were prepared by Pakan Isfahan Company. The aim of this study was the effect of ultraviolet rays at different levels (UVC: 0, 100, 200, 300, 400, 500, 600, and 700 nm) on the activity of photosynthetic pigments and biochemical traits of portulaca oleracea in factorial in a completely randomized design with three replications. After transferring the seeds of portulaca oleracea, the healthy and uniform seeds of this plant were sterilized in 15% sodium hypochlorite solution for 154 minutes and then washed thoroughly with distilled water and placed in a petri dish for germination. Moisture was supplied through filter paper soaked in distilled water. The seeds were planted in pots filled with cocopeat and perlite evenly and watered for 20 days with a halfstrength Hoagland solution. Plants were grown for 20 days at a temperature of 30 ± 2 ° C and a light period of 8.16 (light / dark, respectively). Plants for one week, every other day, and for 3 minutes each time by two fluorescent lamps with a wavelength of 260 nm exposed to ultraviolet C (at a distance of 30 cm from the UV light source with an intensity of 27 (w / m2) were located. The traits studied in this study included chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, phenol, flavonoids, and antioxidant activity. In this study, the effect of ultraviolet light on the activity of photosynthetic pigments and biochemical traits of portulaca oleracea was investigated factorially in a completely randomized design with three replications.Results and Discussion The results of the mean comparison showed that the UV treatment of chlorophyll a, b, total chlorophyll, carotenoid of portulaca oleracea was reduced compared to the control; However, UV treatment of portulaca oleracea significantly increased phenol, flavonoids, and antioxidants compared to the control. The effect of different doses of ultraviolet rays on phenol and portulaca oleracea antioxidants showed that the UVC highest and lowest were 700 and 100 nm, respectively. Decreases in carotenoid content can result in either inhibition of pigment synthesis or their breakdown and degradation. The results of this report indicate significant changes in phenols and flavonoids as compounds it absorbed ultraviolet rays compared to control cells.Conclusion It can be said that excessive exposure to radiation may affect chlorophyll levels by inhibiting chlorophyll biosynthesis or accelerating its degradation. Oxygen is an electron receptor in the electron transport system that produces energy from adenosine triphosphate (ATP) in the body. Under certain conditions, oxygen can be converted to a single electron, creating free radicals. When oxygen is converted to a single electron, it is called active oxygen (ROS). These free radicals cause oxidative stress in plants which oxidative stress leads to damage to macromolecules such as DNA, proteins and so on. Environmental stresses, including UV radiation, produce active oxygen species (ROS) such as hydrogen peroxide (H2O2), superoxide (O2), and hydroxyl radicals (OH), which cause oxidative stress and cause damage to cells, such as DNA. And cause the destruction of these compounds. The plant contains compounds that act as active antioxidants and sweep away active oxygen. In the present study, the observed increase in phenols, flavonoids and antioxidants indicates an increase in the production of free radicals under ultraviolet radiation and shows that the production of these radicals is more than the plant’s defense capacity and has caused damage to plant biological membranes. In summary, the application of controlled ultraviolet light stress can provide a new alternative strategy to increase the productivity of the portulaca oleracea plant. Modulating UVC light in agricultural systems is a promising tool to increase crop production.