| The main variety of ncz-Shennong 9816 in Liaoning Province was chosen and pot cultivation experiment was carried out to study the effect of biochar on rice growth, cadmium chemical forms and contents in different organs under the stress of cadmium. Four cadmium concentration processes of 0,1.2 and 4mg-kg-1marked as CdO, Cd1, Cd2 and Cd4 were set in this text.And three biochar treatments of 0.4 and 40t-hm-2 were set,which the biochar content of each basin applied 0,21,210 gram marked as C0, C21 and C210.The total of 12 experimental groups were set up in this test. The results showed that:1. The effect on rice agronomic characteristics indexes:Under the same condition of biochar added, there was a slight promotion to the rice tiller number, the rice root indexes, and the rice underground dry weight in the low concentration of Cd1, and each index reached maximum. With the increased of concentration of cadmium, each index decreased. The indexes reached the minimum value under the treatment of high concentration Cd4. And the effect of cadmium on rice plant height, rice aboveground dry weight was not significant. In the same cadmium concentration circumstances, with biochar added, the rice root indexes (filling stage and dough stage) and biomass indexes (filling stage and dough stage) were presented the trend of C21> CO> C210, the rice root indexes (tillering stage) were presented the trend of C210> C21> CO.The other indexes such as rice plant height, rice tiller number and biomass indexes (tillering stage) had no obvious change with biochar added.In the treatment of low concentration of Cdl. moderate concentration of Cd2 and high concentration of Cd4, with the increased of biochar added. C21 and C210 compared with C0. the growth of effect of the other agronomic characteristics indexes showed that C21 was better than C210, while the rice root indexes (tillering stage) showed the converse trend. During the whole growth period, the growth effects of agronomic characteristics indexes were various with the different cadmium concentrations.2. The effect on rice photosynthetic and physiological indexes:Under the same condition of biochar added, there was a slight promotion to the rice photosynthetic and physiological indexes such as the rice leaf area, the rice chlorophyll content (a、 b、 (a+b)) and photosynthetic indexes, and each index reached maximum.With the increased of concentration of cadmium, each index decreased. The indexes reached the minimum value under the treatment of high concentration Cd4. In the same cadmium concentration circumstances, with biochar added, the rice photosynthetic and physiological indexes were presented the trend of C21> CO> C210. In the whole growth period of rice, the net photosynthetic rate (A). stomatal conductance (Gs) and transpiration rate (E) were presented a trend of reduing the rise, by contrast, the intercellular CO2 concentration (Ci) showed first decrease after increasing. So the net photosynthetic rate, stomatal conductance and transpiration rate had a positive correlation, while had a negative correlation relateted to the intercellular CO2 concentration. At the same time, high concentration of cadmium inhibited the net photosynthetic rate and transpiration rate, both fell, the intercellular CO2 concentration increased, so it was the dispute stomatal limitation factors leaded to the net photosynthetic rate decline.Under different levels of cadmium concentration, with the increased of biochar added, C2I and C210 compared with CO, all the photosynthetic and physiological indexes showed the trend that C21 was better than C210. During the whole growth period, all indexes were various with the different cadmium concentration.3. The effect on yield indexes:Under the same condition of biochar added, there was a slight promotion to the rice yield indexes such as panicle per pot, the rice grains per panicle, the rice seed setting rate, the rice 1000-grain weight and the rice yield per pot, each index reached maximum.With the increased of concentration of cadmium, each index decreased. The indexes reached the minimum value under the treatment of high concentration Cd4. In the same cadmium concentration circumstances, with biochar added, yield indexes were presented the trend of C21> CO> C210. except the rice grains per panicle in Cd4 treatment showed the trend of C21> C210> CO.In the treatment of low, moderate and high concentrations of cadmium, with the increased of biochar added, C21 and C210 compared with CO, the growth of effect of yield indexes showed the trend that C21 was better than C210. Under the concentration of Cd2 treatment, the level of C21 was better to panicle per pot, the rice seed setting rate and the rice yield per pot than other concentrations of C. Under the concentration of Cd4 treatment, compared with other concentrations, the level of C210 was better to the rice grains per panicle and the rice 1000-grain weight.4. The effect on cadmium chemical forms in different organs:Under the same condition of biochar added, with the increased of cadmium concentration, the six different cadmium chemical forms in rice were increased and presented the trend of Cd4> Cd2> Cd1> CdO. In the same cadmium concentration circumstances, with biochar added, ethanol extract (F1), deionized water extract (F2), sodium chloride extraction states (F3), acetic acid extraction (F4), hydrochloric acid extraction states (F5) were declined, and C210 obtained the minimum value, but residue state (F6) was increased. Above all, the effect of biochar was C210> C21> CO.Under different cadmium concentration, the decline of C210 was greater than C21 on the content of F1-F5. and overall, the drop effect in high concentration of Cd4 treatment was most obvious. The C210 growth effect of concentration of F6 was better than C21. and the same in the Cd4 treatment reached the maximum growth.The proportion of different chemical forms in rice different organs was different. The proportion of F3 in various organs was superior in concentration, especially in panicle. The F4 in root accounted for a large proportion. The proportion of other chemical forms fluctuated according to different growth periods and different organs. 5. The effect on cadmium concentrations in different organs:Under the same condition of biochar added, with the increased of cadmium concentration, the cadmium concentrations in different organs were increased and presented the trend of Cd4> Cd2> Cd1> CdO. different organs were showed the trend of root>stem>leaf> rice hull>polished rice. In the same cadmium concentration circumstances, with biochar added, the cadmium concentrations in different organs were declined and showed the trend of C210< C21< C0. |
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