水稻光合碳在植物-土壤系统中的分配及其对CO2升高和施氮的响应

采用¹³C-CO₂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CO₂浓度升高(800 μL·L^-1)和施氮(100 mg·kg^-1)的响应.结果表明: CO₂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.CO₂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.CO₂浓度升高使光合¹³C在孕穗期向土壤的输入显著增加,然而施肥并没有促进由CO₂浓度升高驱动的光合¹³C在土壤中的积累,而且还降低了土壤中的光合¹³C的分配比例.综上,CO₂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.

Allocation of rice photosynthates in plant-soil system in response to elevated CO2 and nitrogen fertilization.

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 with ¹³CO₂. 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 assimilated ¹³C to the soil at the booting stage. N fertilization did not promote the elevated CO₂-induced stimulation of assimilated ¹³C allocated to the soil, and it even decreased the proportion of assimilated ¹³C 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.