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.

Study the effect of ultraviolet radiation on the mechanical properties of vulcanizing rubber belts models

This study includes an experimental work to determine the effect of ultraviolet radiation (uv-rays) on the mechanical behavior of the conveyor rubber vulcanizing, which used in various transport operations, and in the cement plant Tartus. In this work, it has been prepared different samples of belts, and they were exposed to uv radiation at differente times, then they were tested to know its wear and tensile strength. The results were compared with samples similar to the samples tested, which was not exposed to the rays of UV, and with other samples exposed to temperatures, and that in order to reach the ideal conditions for the use of these belts, which ensures longer period of use and safe conditions. This study showed that uv-rays increase the average of wear and the tensile strength of belts.