| Land is the foundation of people’s livelihood and the basis of human existence.The food,resources and environment problems faced by the world are closely related to the land.China is a large agricultural country with a large population,and the safety of farmland is related to the long-term livelihood of the people.Rice is an important crop in China.Heavy metal contaminated farmland has a negative impact on rice growth.It not only reduces the grain yield,but also absorbs and accumulates heavy metals in the edible part of the crop and enters the human body through the food chain,thus threatening human health.In this paper,hydroponic culture and soil culture were used to study the effects of different agronomic management measures on rice growth and Cd,As,Ni uptake and accumulation under Cd,As,Ni stress.The main results were as follows:（1）Under Cd stress,adding 1 mg·L-1 boric acid,10μmol·L-1 melatonin,0.5mg·L-1 sodium molybdate and 1 mmol·L-1 sodium silicate could promote the germination of rice seeds and the growth and development of rice seedlings under Cd stress.Under the stress of 5μmol·L-1 Cd,the addition of four amendments increased the germination rate of rice seeds by 11.1%,10.0%,11.1%and 10.0%,respectively,and the germination potential was increased 17.8%and 17.8%,respectively,compared with CK treatment.At the same time,the addition of four amendments could reduce the content of Cd in rice.When the concentration of Cd was 1μmol·L-1,the Cd content in rice roots decreased by 32.6%72.5%and the Cd content in rice seedlings decreased 0.4%75.1%.When the concentration of Cd was 5μmol·L-1,the Cd content in rice roots decreased by 4.3%63.1%and the Cd content in rice seedlings decreased 23.1%50.5%.（2）The roots and shoots growth of rice was inhibited under As stress.Adding 10μmol·L-1 melatonin,150μmol·L-1 ferric sulfate,0.5 mg·L-1 sodium molybdate and 1mmol·L-1 sodium silicate,the roots and shoots length and roots and shoots weight of rice were improved.The maximum efficiency of adding four amendments to reduce As content in rice roots was 25.5%,31.7%,28.6%and 75.5%,respectively,and the maximum efficiency of reducing As content in rice shoots was 21.2%,63.8%,26.1%and 78.2%,respectively.With the increase of As concentration,the contents of chlorophyll a,chlorophyll b,total chlorophyll and carotenoid in rice leaves decreased significantly.Under As stress,the addition of melatonin,ferric sulfate and sodium molybdate increased the chlorophyll a content by 4.1%64.3%,the chlorophyll b content increased by 4.6%55.5%,the total chlorophyll content increased by7.3%71.9%,and the carotenoid content increased by 8.7%56.6%.However,sodium silicate decreased chlorophyll a,chlorophyll b and total chlorophyll contents.（3）Under Ni stress,the increase of Ni concentration resulted in a gradual increase of Ni uptake and accumulation in rice.When 10μmol·L-1 melatonin,10 mmol·L-1calcium chloride,0.5 mg·L-1 molybdate and 1 mmol·L-1 sodium silicate were added,the maximum efficiency of reducing Ni content in rice roots was 27.8%,19.5%,13.4%and 35.0%,respectively.The content of photosynthetic pigment in rice leaves decreased gradually.In addition to sodium silicate,the other three kinds of amendments could increase the content of photosynthetic pigment in rice leaves.Ni stress increased the content of MDA and decreased the activity of CAT,POD,SOD enzyme in roots and shoots.The maximum efficiency of adding four amendments to reduce the MDA content was 17.7%,and to increase the activity of CAT,POD,SOD128.2%,67.8%and 120.9%respectively.In pot experiment,the effect of rice uptake and accumulation of heavy metals in soil polluted by Cd,As,Ni was studied by means of water management and adding amendments.Under the condition of no flooding,the content of Cd,Ni is higher and the content of As is lower,but it was opposite under the condition of flooding.The addition of Fe+lime reduced the Cd content in rice shoots and grains by 2.27 mg·kg-1and 0.20 mg·kg-1,and the As content decreased by 5.38 mg·kg-11 and 0.48 mg·kg-1.The Ni content in rice shoots and grains was decreased by 19.7 mg·kg-1 and 1.51mg·kg-1 at most with the addition of Si.The pH of soil can be adjust by water management and adding amendments.The pH of soil under the condition of no flooding is higher than that of flooding condition.The addition of Si and lime could significantly increase the pH of soil.The addition of Si+Mo treatment in Cd,As-contaminated soil had no significant effect on K and Mg contents in rice shoots,but decreased the content of Ca,Mn.Fe+lime treatment had no significant effect on K,Ca,Mg contents in rice shoots,but decreased Mn contents.In the Ni contaminated soil,the addition of Mo and Ca increased the Mn content in rice shoots.The Ca,Mn content was increased by adding Si under flooding treatment. |
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