Reaction Of Rice Seedling To Cd Stress And The Relation With Cd Accumulation Characteristic In Whole Growth Period Under Cd Stress

Effect of heavy metal Cd on Cd uptake and Cd-resistant indices in rice seedlings grown in hydroponics was studied under the condition of artificial illumination incubator. The biological effects of Cd on rice plants grown in pots during whole growth period were also analyzed. The main results were as follows:1. The growth of rice seedlings was sensitive to Cd stress. The seedling height decreased significantly at a lower Cd concentration, and with the increase in Cd concentration, the stress index increased significantly. Dry matter production of seedlings was also very sensitive to Cd stress. Responses of root growth to the Cd stress showed differences among varieties.2. Cd stress significantly inhibited the synthesis of chlorophyll, especially for the synthesis of chlorophyll a, in rice seedlings. Synthesis of chlorophyll of seedlings was sensitive to Cd concentration, and with the increase in Cd concentration, chlorophyll content reduced significantly. The synthesis of chlorophyll of rice seedlings under Cd stress reacted differently among varieties. Japonica rice varieties were more sensitive and the chlorophyll content declined more under Cd stress. In Cd stress conditions, MDA content of rice seedlings increased, SOD activity increased, and with the Cd concentration increased, they increased more. Activities of CAT and POD were complex.3. Rice growth and development were affected significantly under Cd stress during whole growth period, however, the reactions varied with rice varieties. The effects of Cd stress on SPAD in leaves at heading stage were not significant for most varieties. Plant height was significantly shorter than control, but there were still a few varieties insensitive. Effects of Cd stress to total material production were increased or decreased. Changes in grain yield and dry material production were similar to those trends. Cd stress reduced spike lets per panicle. The effect of Cd on other yield components was complex.4. It showed strong Cd accumulation under lower Cd concentration. With the Cd concentration increased, accumulation increased but accumulation index decreased. Cd concentration in roots was much greater than that in the aerial parts. Cd distribution in different parts of aerial parts was quite different, but the concentration trend was consistent. More Cd accumulated in stem and sheath than in leaves and grains. There was a significant correlation between Cd absorption and accumulation in seedling stage and Cd accumulation during whole growth period, indicating that the characteristics of Cd uptake and accumulation of rice showed obvious manifestation in the seedling period.5. The responses of plant height and chlorophyll content in seedling period to Cd stress and the growth effects to Cd stress in the whole growth period were not obviously contacted .There was no correlation with Cd content of aerial parts in mature period .It showed that seedling plant height stress index under Cd stress could reflect variety characteristics clearly, but it could not represent the Cd stress effects of plant growth in mature period .