水稻光合碳在植物-土壤系统中的分配及其对CO_2升高和施氮的响应

Allocation of rice photosynthates in plant-soil system in response to elevated CO_2 and nitrogen fertilization

采用^(13)C-CO_2进行连续标记,研究水稻分蘖期和孕穗期光合碳在植株-土壤系统中的分配及其对大气CO_2浓度升高(800μL·L^(-1))和施氮(100 mg·kg^(-1))的响应.结果表明:CO_2浓度升高显著提高分蘖期根系生物量和孕穗期地上部生物量,并使生物量根冠比在分蘖期增加,而在孕穗期减小.CO_2浓度升高条件下,施氮使水稻地上部分生物量增加,却显著降低了孕穗期水稻根系生物量.CO_2浓度升高使光合^(13)C在孕穗期向土壤的输入显著增加,然而施肥并没有促进由CO_2浓度升高驱动的光合^(13)C在土壤中的积累,而且还降低了土壤中的光合^(13)C的分配比例.综上,CO_2浓度升高显著提高了稻田土壤光合碳输入,促进稻田有机碳周转;施氮促进了水稻地上部的生长,却降低了光合碳向地下的分配比例.

To examine the allocation of rice photosynthates and its response to the elevated CO2(800 μL·L^（-1）） and N fertilization(100 mg·kg^（-1）） at both tillering stage and booting stage in plant-soil system,rice was continually labelled with13CO2. The results showed that the rice root biomass at the tillering stage and the shoot biomass at the booting stage were significantly increased under elevated CO2. Elevated CO2 increased the rice biomass and root-shoot ratio at tillering stage,but reduced it at booting stage. Under elevated CO2,N fertilization promoted shoot biomass during rice growth,but significantly decreased the root biomass at booting stage. Elevated CO2 significantly increased the allocation of assimilated13C to the soil at the booting stage. N fertilization did not promote the elevated CO2-induced stimulation of assimilated13C allocated to the soil,and it even decreased the proportion of assimilated13C in the soil. In summary,elevated CO2 increased the photosynthetic C allocation into soil and promoted the turnover of soil organic carbon in paddy soil.N fertilization enhanced rice shoot biomass but decreased the belowground allocation of photosynthetic C.