Study On Effects Of Lead On Growth And Development Of Cucumber (Cucumis Sativus L.) Seedlings

Heavy metal pollution is one of the most serious environmental problems in recent years. Heavy metal pollution in soil degenerates soil fertility, decreases crop yield and product quality, deteriorates water environment, and endangers human health through food chain. Study on heavy metal pollution became one of the hottest academic areas. The cucumber seedling were used to study how the lead (Pb) contamination impacts on the growth and development of cucumber seedlings, especially the change of endogenous phytohormones, polyamines, antioxidation protection enzyme system, biochemical and physiological characteristics. The main results are as follows:1. Effects of lead on germination, early growth and development, some physiological and biochemical characteristics of cucumber seedlingsThe absorption and distribution of lead was different in cucumber seedlings. Lead absorbed mainly accumulates in root, while a small portion was transported to stems and leaves. The lead amount in leaves and roots of cucumber seedling increased under the exogenous lead treatment. It was also found that the germination was promoted within lead mass concentration range of 100-200 mg·L^-1 and hold down under lead mass concentration 300⁹00mg·L^-1Growth accelerating of cucumber seedlings was observed within range 100²00mg·L^-1 lead mass concentration, meanwhile growth was restrained under lead mass concentration of 300⁹00mg·L^-1, and the restraining impact was getting more obvious with the increase of lead mass concentration. High mass concentration of lead induced adventitious roots. Dry weight of cucumber seedling was negatively related to lead mass concentration under lead treatment.Chlorophyll amount in leaves increased within lead mass concentration range of 100-700mg·L^-1, but chlorophyll amount decreased when the lead mass concentration reached 900mg·L^-1 Palisade tissue and spongy tissue in leaves became more tighter arrangment, especially palisade tissue layers increased from one to three.MDA and proline amounts in cucumber seedlings increased continually with increase of lead mass concentration, and they were positively related to lead mass concentration. Cell membrane permeability increased with the increase of lead mass concentration, and the transformation tendency was in conformity with MDA change.2. Effect of lead on antioxidation protection enzyme system in aerial parts of cucumber seedlingWithin lead mass concentration of 100⁵00mg·L^-1, SOD activity in aerial parts...