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.

Using of Photosynthetic electron transport as an indicator of photosynthesis efficiency

Photosynthetic transport was studied as an indicator of photosynthesis efficiency in two bread wheat cultivars (ACSAD 899, ACSAD 1059) under the influence of one of the salt stress. This study was carried out in sand cultures irrigated with nutrient solution in a growth chamber, and 14 days seedlings were treated with 100 mM of sodium chloride. Later the electron transport rates in those plants thylakoids were measured in 21, 28, 35 days of the experiment. Electron transport rates decreased in ACSAD 899 and reached 57% in the last day of the experiment, while it was 24.6% in ACSAD 1059. The decrease in photosynthetic electron transport rate leads to a decrease in the reduction rate of CO2 and the plant productivity as a consequence. Therefore, it could be used as criterion to express photosynthesis.