Study On Physiological Change And Lead Absorption Effect Of Lotus In Lead Nitrate Environment

Through the method of planting lotus (Nelumbo mucifera) in water tank, this paper studied the lead accumulations in various organs of Lotus and their impact on growth and physiology under different Pb(NO3)2 solution concentrations. Results showed that:1. In low concentration (≤100mg/l) Pb(NO3)2 solution , as concentration increased,the poisonous effect of lead on the lotus deepened,and the symptoms were significantly. In high concentration (>100mg/l) Pb(NO3)2 solution,as concentration increased, the poisonous effect eliminated due to the influence of NO3-, what's more, the plant grew better than the contrast.2. In low concentration (≤100mg/l) Pb(NO3)2 solution,Pb2+ stress played a leading role,and the chlorophyll content and photosynthetic rate of Lotus leaf reduced significantly,which indicated a distinct negative correlation between chlorophyll content and the lead content of leaves; lead could destroy the integrity of Lotus leaves cell membrane,and raised the content of cell membrane lipid peroxidation product malondialdehyde (MDA) and increased the penetration of membranes; the main osmotic regulation substance soluble protein reduced as the solution concentration increased; the activities of superoxide dismutase (SOD),peroxidase (POD),catalase (CAT) in Lotus leaf increased as the concentration of the solution increased. In high concentrations (>100mg/l) Pb(NO3)2 solution,Pb2+ inhibition gradually eliminated and NO3- effect highlighted, plant growth and development promoted, lead content of the organ declined,the trend of various physiological indicators were reversed to that in low concentration.3. In different concentrations, Lotus plants could absorb lead through the roots and accumulate in various organs. The order of lead accumulation intensity in various organs was: fibrous root > petiole > bud> leaves > rhizome. Most of the lead absorbed by Lotus accumulated in the roots; lead accumulation in various organs increased as Pb(NO3)2 solution concentration raised, and reached peaks in different concentrations, then as the concentration raised, the Pb content declined,while, when reached the lowest points, they possessed the positive correlation again. In summary, along with the increased of the solution concentration, the changing law of Pb content presented the oblique "N" shape, namely: increased-declined-increased slightly.4. Lotus plants possessed strong endurance and great repair potential against the lead pollution. But the Pb content ratio between aboveground part and underground part of Lotus was quite low,so it was difficult to purify water by harvesting the aboveground part in successive years. While, the costs would inevitably increased if removes the roots together. Through the experimental analysis, this paper held that the Lotus was not quite valuable in repairing heavy-metal contamination of water.5. Experiment testified that nitrogen fertilizer could ease the poisonous effect of lead contamination,so applying nitrogen fertilizer in the lead contaminated water was an effective method to improve the growth and development of lotus.This paper studied the effect of Pb(NO3)2 on the growth and the lead accumulating rule of Lotus organs. Besides, Lotus physiological response, Lotus'impact on the environment and its edible safety issues were discussed.