Comparison On The Yeild And Cadmium Accumulative Of Different Rice Varieties Under Cadmium Stress

With the economic take-off, the environment we live by has been seriously damaged. Human beings immoderately pour huge amount of secondary pollutants into surroundings in the pursuit of development. This has worsened the global environment day by day. Cadmium pollution as one of typical environmental pollutions covering widely areas with difficulties to be treated has been concerned by people. Since cadmium ion migrates and gathers easily with the environment, it harms rice seriously not only influencing the growth of rice but also harmful after absorbed and accumulated in human body.The research makes experiments on semilate rice and late rice through the method of potting so as to study and discuss production of different rice varieties and cadmium accumulative difference in each part under cadmium stress environment. The result shows:1、Under different treatments, cadmium contents in different varieties of rice show:root> stem> leaf> chaff> coarse rice, and cadmium contents in each part of the plant under cadmium stress have significantly increased. Under cadmium stress, cadmium content in each part of rice has close relationship with the gene type and subspecies. Cadmium contents in each part of semilate rice present roughly:general japonica rice> general nonglutinous rice> hybrid rice. Late rice is greatly influenced by rice variety differences. Cadmium content in japonica rice coarse rice is obviously lower than nonglutinous rice. It can be seen that semilate rice is suitable for planting with nonglutinous rice variety, and late rice is more sutable for planting with japonica rice variety. Regarding all experimental subjects, Yongyou 1540 semilate rice has the best anti-cadmium property, Wuyun jing 27 the weaker H you 515 late rice has the best anti-cadmium property, and Yongyou 1540 the weaker.2、In different growth period, cadmium content in the stem of hybrid rice shows a trend of declining first and increasing later and the content increases the most obviously in the milk-ripe stage. Cadmium content in the leaf is greatly influenced by variety difference in the whole growth period but the differential influence of genotype and subspecies is not obvious. Cadmium content in the grain of rice increases from the full heading stage gradually with the passing of growth period, and reaches the highest in the stage of yellow ripeness. Wuyun jing 27, the semilate rice increases most obviously influenced by cadmium stress. Yongyou 1540, the late rice, cadmium content in its grain increases the most obviously.3、Cadmium cumulative distribution in rice has notable differences with the influence from genotype. Under cadmium stress, cadmium cumulant in different part of different rice varieties has significantly increased. Seeing from the cadmium cumulant proportion in different part in different stages, differences in varieties have close connection with cadmium cumulative distribution in rice. In tillering stage, except cadmium cumulant in the leaf of two varieties Huanghua zhan and Yongyou 5550 has increased in proportion, other experimental subjects have reduced. Cadmium cumulative distribution in each part in full heading stage and pustulation period is greatly influenced by variety difference. But there is no predictable rule can be seen regarding the difference between genotype and subspecies. Cadmium ion migration and accumulative ability in the grain of semilate rice and late rice in stage of yellow ripeness is larger than hybrid rice. This shows that hybrid rice has good anti-cadmium property than conventional rice. It specifically reflects as that, the transforming ability of cadmium ion from the stem to grain of conventional rice is stronger than hybrid rice making the cadmium cumulant in the grain of rice increase sharply. On the other hand, the ability to prevent cadmium ion transporting upward in hybrid rice is stronger than conventional rice.4、Cadmium stress influences the chlorophyll and photosynthesis of rice reflecting as reducing the chlorophyll contents, net photo synthetic rate and intercellular CO₂ concentration, reducing the stomatal conductance of the leaf and increasing the leaf transpiration rate. Cadmium stress has reduced the chlorophyll relative content in all experimental rice to different degrees. Yongyou 538 is the rice variety influenced litter by cadmium stress in normal case, H you 518 for late rice. The net photosynthetic rate, stomatal conductance and transpiration rate are influenced greatly by rice varieties. There are differences on genotype and subspecies from the influence of cadmium stress on the leaf intercellular CO₂ concentration. The semilate rice reflects as conventional rice> hybrid rice but late rice as nonglutinous rice>japonica rice. Under normal handling, all physical signs in Yongyou 538 of semilate rice influenced by cadmium stress have increased. But Zhongzao 39 of the late rice has the most obvisous increase in all physical sings.5-. Under the influence of cadmium stress, TKW, ripening rate, plant height and ear length of rice reduce but not obviously. Except that the ripening amount of Yongyou 538 in semilate rice has increased 39% comparing with the normal group, other varieties of rice have reduced in different degrees. Except that the production output of Yongyou 538 in semilate rice has increased 34%, other varieties of rice have reduced. Zhongzao 39 of late rice has the minimum output reduction range. All varieties of semilate rice are influenced by genotype. Conventional rice has a larger output reduction than hybrid rice. But all varieties of late rice are influenced by subspecies. all varieties of japonica rice have a larger output descend range than nonglutinous rice.