大气CO2浓度升高对红桦幼苗根系的影响

应用封闭式生长室系统,研究了CO2浓度升高对红桦(Betula albosinensis)幼苗的根/冠、粗根和细根的干质量、非结构性碳水化合物类含量、碳含量和碳/氮、氮和磷的含量及氮磷吸收量的影响。结果表明:CO2浓度升高使红桦幼苗粗根和细根的干质量增加,同时根/冠值显著升高,表明CO2浓度升高使红桦幼苗生物量向根系的分配增加;与对照相比,粗根的还原糖、蔗糖和总可溶性糖含量显著增加,而在细根中没有显著变化;粗根、细根的淀粉和总的非结构性碳水化合物含量显著增加;CO2浓度升高下粗根和细根的碳含量有升高的趋势但未达到显著水平,同时氮含量降低,碳/氮值升高;氮的吸收量在粗根和细根中均无显著变化。上述结果表明,CO2浓度升高下红桦幼苗根系氮含量下降是由非结构性碳水化合物(主要是淀粉)含量升高和(或)根系生物量增加产生的稀释效应引起的。

Effects of elevated atmospheric CO2 concentration on Betula albosinensis seedling roots

By using top-enclosed growth chamber, this paper studied the effects of elevated atmospheric CO2 concentration on the root/ shoot (R/S) ratio of Betula albosinensis seedlings, and on the dry mass and non-structural carbohydrate, C and N contents of their coarse and fine roots. The results showed that elevated CO2 increased the R/S ratio and the dry mass of both coarse and fine roots, indicating that the seedlings under elevated CO2 allocated more biomass to their belowground part. Compared with control (CK), elevated CO2 increased the contents of reducing sugar, sucrose, and total soluble sugar in coarse roots significantly, but had less effect on those in fine roots. Elevated CO2 increased the contents of starch and total non-structural carbohydrate (TNC) both in coarse roots and in fine roots. Under elevated CO2, the carbon content in coarse and fine roots had an unsignificant increasing trend, while the nitrogen content decreased significantly, which resulted in an increase of C/N ratio. No significant change was observed in the nitrogen uptake by both coarse and fine roots. The decline of root nitrogen content under elevated CO2 was mainly caused by the dilution effect of increasing root biomass and the increase of non-structural carbohydrate (starch in particular) content in roots.