Influence of lead stress on growth, photosynthesis and lead uptake in the seedlings of cotton.

Heavy metals, such as lead, cadmium, copper, chromium are major environmental pollutants, especially in areas that have high anthropogenic activities. Among heavy metals, lead (Pb) is a potential pollutant that readily accumulates in soils, sediments and is poisonous. The hydroponic experiment was planned to assess the morphological , photosynthetic and lead uptake responses of cotton to lead stress. In this experiment plants were grown in the nutrient medium with four lead (Pb) levels (0, 25, 50 and 100µM) in the form of lead nitrate Pb(NO3)2 . Plant growth, biomass, chlorophyll contents, photosynthesis and lead uptake of cotton plants were recorded. Lead (Pb) treatment had negative effects on growth parameters compared with the control. Results showed the non- significant differences between the plants subjected to low lead (Pb) level (25µM) and lead untreated ones (control). At high lead levels (50 and 100µM) all growth parameters were affected badly and a significant decrease in the plant biomass, chlorophyll contents, photosynthetic attributes were observed. At high concentrations of lead (Pb) growth abnormalities such as stunted growth, wilting and leaf abscission also occurred in cotton plants. From our present results, we can conclude that cotton growth and photosynthesis were decreased significantly at higher lead levels but was not affected at lower lead level.