Effect Of Cd And Zn Stress On Seed Germination, Physiology And Biochemistry Of Nelumbo Nucifera

With the development of industrialization, urbanization and agricultural modernization, heavy metals discharged into the environment increase with years. Heavy metals contamination has become a serious problem in environment and society, which poses a threat to human health and life quality. Taking the widely cultivated, history glorious and utility diversified lotus (Nelumbo nucifera) as research object, adopting pot experiment and combining with germination test, this paper studied the effect of Cd and Zn stress on seed germination, physiology and biochemistry of lotus; probed the variation laws of chlorophyll content, plants membrane permeability, soluble protein content in lotus, and seed germination under Cd and Zn stress of different concentration and different treatment time; explained the toxicant mechanisms of heavy metals against plants. It intends to provide the reference for the study on lotus' application and phytoremediation under heavy metals water pollution. Results are as follows:1. Cd and Zn stress affected the seed germination. Low concentration improved the germinability (Cd≤5mg/L,Zn≤100mg/L) and igermination percentage (Cd≤15mg/L, Zn≤20mg/L), while high concentration displayed inhibiting function (Cd≥15mg/L,Zn≥150mg/L;Cd≥30mg/L,Zn≥50mg/L), which indicates that heavy metals could hurt the growth and development of lotus in the beginning period. Cd and Zn stress affected chlorophyll content, and it increased obviously under short time and low concentration stress, decreased under long time and high concentration stress. Chlorophyll is the key material in photosynthesis, the decrease of which could affect the photosynthesis, the synthesis of organic materials and the growth and development of lotus.2. Under Cd and Zn stress, during each period after treatment, the relative electric conductivity was higher than the contrast, and it increased or kept a high level with the increase of treatment concentration; in each treatment, the relative electric conductivity increased with the extension of time. MDA in lotus leaf accumulated massively under heavy metals Cd and Zn stress, and the accumulation amount increased with concentration's increasing and time's extension. Materials in cells exosmosed heavily; electrical conductivity increased; MDA content increased; the membrane structure of cells and main cellular organs was destroyed, and the normal physiology activity of plants was influenced, which indicates that lotus is affected by the two heavy metals in different degrees.3. Lotus presented a certain resistivity to Cd and Zn stress. Under low concentration treatment, the soluble protein content increased as the concentration increased; under high concentration and long time treatment, it declined. Soluble protein could raise the osmotic potential of cell inchusion, form compound with heavy metals, and lower the affection of heavy metals. In antioxidative enzyme system, the activities of SOD, POD and CAT were enhanced with the stress concentration increasing in early and medium-term of the experiment; in late-stage they presented declined trend under high concentration treatment, but still in a high level. The above results show that lotus could react positively to Cd and Zn stress; it has some endurance and adaptability to heavy metals Cd and Zn, and it has good prospects in the beautification and abatement of city heavy metals contaminated waters.