Studying the Effectiveness of Polyethylene in Limiting the Effect of Ultraviolet Radiation (UV-B) on Photosynthesis Pigments and Photosynthetic Electron Transport in the Leaves of Young Sun Flower Plants (Helianthus sp.)

Young sun flower plants were exposed to ultraviolet radiation of the type UV-B (295 nm) for 3 days (2 hours per day) with or without excluding the UV-radiations using polyethylene layers (blue and transparent) (0.5 mm thick). The amount of photosynthesis pigments was measured whereby a variation in the chlorophyll contents. Chlorophyll a (chl.a) was noticed at these rates (without covering 19.59%, transparent polyethylene 3.40%, blue polyethylene 1.66%), chlorophyll b (chl.b) at rates (7.81, 25.13, 22.79%) and the total chlorophyll content (2.88, 21.76, 20.53%), while the amount of carotenoid pigments has increased in the studied samples (24.45, 19.23, 17.32%). A decrease in the rate of photosynthetic electron transport has also been noticed (88.04, 78.71, 58.81%) in the plant samples exposed to ultraviolet radiation (on the third day) without UV excluding and with transparent and blue polyethylene successively. All results were compared to the sample which was not exposed to radiation. All results indicate the negative effect of ultraviolet radiation on the chlorophyll content and the rate of photosynthetic electron transport, therefore, on photosynthesis and the productivity of sun flower plants. They also point out the importance of carotenoid pigments in protecting chlorophyll pigments from the negative effects of this radiation. Results showed the clear positive effect of polyethylene layers, specifically the blue one, in protecting plants against this radiation.