用^(13)C标记法研究光合碳在枫香和山乌桕幼苗体内的留存及分配动态

Retention and distribution dynamics of photosynthetic carbon in Liquidambar formosana and Sapium discolar seedlings by ^(13)C labeling

光合碳在植物体内的留存和分配规律对评估植物的固碳能力具有重要意义.以亚热带落叶树种枫香(Liquidambar formosana)和山乌桕(Sapium discolar)幼苗为研究对象,运用^(13)C脉冲标记法室内培养植株,自标记完成跟踪至叶片凋落和重新展叶,测定不同时段各器官δ^(13)C值、分配比例和^(13)C固定量.结果显示,标记3 d后,枫香和山乌桕^(13)C的固定量分别为14.42 mg/株和20.36 mg/株,各器官分配比例为叶片>枝条>粗根>细根.标记30 d后,枫香和山乌桕固定的^(13)C留存比例分别为79.34%和91.25%.标记108 d后(落叶期),枫香和山乌桕固定的^(13)C留存比例分别为65.40%和37.96%,^(13)C分配比例均转变为粗根>枝条>细根.标记180 d后(展新叶期),枫香和山乌桕固定的^(13)C留存比例分别为61.90%和14.06%.两个树种的^(13)C均表现为从根系向新叶转移,转移比例分别为7.34%和13.91%.上述结果表明:枫香光合固碳能力低于山乌桕,但暗呼吸速率也低于山乌桕,光合碳在体内的留存量则高于山乌桕;两种落叶植物在生长阶段固定的光合碳首先富集在叶片,之后的分配调整在不同物种间存在差异;落叶期光合碳由叶片向根系中转移,展叶期则重新由根系向新叶中转移.上述研究结果对落叶植物碳汇能力的研究具有参考意义.

The retention and distribution of photosynthetic carbon in plants is of great significance to evaluate the carbon sequestration capacity of plants.In this study,the subtropical deciduous tree species Liquidambar formosana(LF)and Sapium discolor(SD)seedlings were used as research objects,and the plants were cultivated indoors using the^(13)C pulse labeling method.From the completion of labeling to leaf falling and re-spreading,theδ^(13)C value,distribution ratio,and fixed amount of^(13)C in each organ at different time periods were measured.The results showed that after labeling for 3 days,the amount of^(13)C fixation was 14.42 mg/plant and 20.36 mg/plant in LF and SD,respectively.The distribution ratio of each organ was in the order of leaves>branches>coarse roots>fine roots.After labeling for 30 days,the fixed^(13)C retention ratios of LF and SD were 79.34%and 91.25%,respectively.After labeling for 108 days(deciduous stage),the fixed^(13)C retention ratios of LF and SD were 65.40%and 37.96%,respectively.The order of distribution ratios of^(13)C in each organ of the two tree species was coarse roots>branches>fine roots.After labeling for 180 days(new leaf stage),the fixed^(13)C retention ratios of LF and SD were 61.90%and 14.06%,respectively.The^(13)C of the two tree species showed transfer from the roots to new leaves.The transfer ratios were 7.34%and 13.91%,respectively.These results indicate that the photosynthetic carbon fixation capacity of LF was lower than that of SD,and the dark respiration rate was also lower than that of SD.Therefore,the retention of photosynthetic carbon in the body of LF was higher than that of SD.The photosynthetic carbon fixed during the growth stage of deciduous plants is first enriched in the leaves.Subsequent allocation adjustments varied across species.During the deciduous stage,photosynthetic carbon is transferred from the leaves to the roots.During the leaf-expanding stage,it is transferred from the roots to new leaves.This study is significant for the study of the carbon sink capacity of deciduous plants.