Study On Cadmium Absorption Time Kinetics And Physiological Response Of Different Rice Varieties

Cadmium pollution incident in rice has become a widespread concern of the state and society,in order to understand soil Cd²⁺adsorption characteristics in the different types of rice,a solution culture experiment was established under four cadmium accumulation rice cultivar with the high Cd accumulation cultivars?HCAs?—Yuzhenxiang?A1?and Tianyouhuazhan?A2?—and the low Cd accumulation cultivars?LCAs?—Xiangwanxian 12?B1?and Jinyou59?B2?to examine the Cd absorption and transfer time kinetic characteristics at stage of seedling and heading,and the Light response of the flag leaf of the rice under the cadmium stress.The main conclusions are as follows:?1?The root and shoot Cd accumulation time kinetic characteristics of the 4 cultivar were all described with Michaelis-Menten equation,?value of their root and shoot all showed like A1 and A2?HCAs?>B1 and B2?LCAs?.The Cd translocation efficiency showed a significant downward trend with prolonging of stress time,and A1 and A2?HCAs?were higher than those of B1 and B2?LCAs?.The correlation analysis showed that there was a significant positive correlation between Cd concentration in shoots and roots and Cd translocation efficiency of root to shoot in different rice varieties.?2?The total amount of Cd accumulation at the heading stage in all organs of rice was consistent with that at seedling stage.The Cd accumulation time kinetic characteristics were all described with Michaelis-Menten equation,?value showed like A1>B1.The correlation analysis showed that there was a significant positive correlation between Cd concentration in shoots and roots and Cd translocation efficiency of root to shoot in different rice varieties.Cadmium content of stem and leaf increased with the increase of root cadmium content,and the growth rate was expressed as the stem>leaf.There was a significant negative correlation between the root activity and root cadmium content under A1 B1,which correlation coefficient was 0.682 and 0.573 respectively.?3?The Cd stress has significant effect on the PS?chlorophyll fluorescence parameters.The PS?photosynthetic activity was inhibited under Cd stress,but being recovered in some extent later.There exist differences for the effect of Cd stress on the PS?chlorophyll fluorescence parameters among different growth period and rice cultivars.More specifically,the rice leaf at stage of seedling and the LCAs are more sensitive to the Cd stress.Under the Cd stress,the excitation energy was mainly dissipated by the photosynthetic activity at the stage of seeding,while by the antenna systems at the stage of heading.