Analysis of plant photosynthesis and post-photosynthetic fractionation can improve our understanding of plant physiology and water management. By measuring δ13C in the atmosphere, and δ13C of soluble compounds in leaves and branch phloem of Platycladus orientalis, we examined discrimination pattern, including atmosphere-leaf discrimination during photosynthesis (ΔCa-leaf) and leaf-twig discrimination during post-photosynthesis (ΔCleaf-phlo), in response to changes of soil water content (SWC) and atmospheric CO2 concentration (Ca). The results showed that ΔCa-leaf reached a maximum of 13.06‰ at 95%-100% field water-holding capacity (FC) and Ca 400 μmol·mol-1, and a minimum of 8.63‰ at 35%-45% FC and Ca 800 μmol·mol-1. Both stomatal conductance and mesophyll cell conductance showed a significant linear positive correlation with ΔCa-leaf, with a correlation coefficient of 0.43 and 0.44, respectively. ΔCleaf-phlo was not affected by SWC and Ca. Our results provide mechanism of carbon isotopes fractionation and a theoretical basis for plant survival strategies in response to future climate change.
对植物光合和后光合分馏进行分析,有助于提升对植物生理和水分管理等的认识。本研究通过测定大气、侧柏叶片和枝条韧皮部可溶性化合物的δ13C,探讨了光合作用时大气和叶片间碳同位素的分馏(ΔCa-leaf)和光合作用后叶片到枝条间的碳同位素分馏(ΔCleaf-phlo)对土壤含水量(SWC)和大气CO2浓度(Ca)的响应。结果表明: ΔCa-leaf在SWC为田间持水量(FC)的95%～100%(95%～100%FC)且Ca为400 μmol·mol-1时达到最大值(13.06‰),在SWC为35%～45%FC且Ca为800 μmol·mol-1时达到最小值(8.63‰);气孔导度和叶肉细胞导度均与ΔCa-leaf呈显著线性正相关,相关系数分别为0.43和0.44;而ΔCleaf-phlo并未受到SWC和Ca的显著影响。本研究不仅可以提高对碳同位素的分馏机制的认识,而且可以为植物对未来气候变化的生存适应性提供理论依据。.
Keywords: soil water content|CO 2 concentration|carbon isotope|photosynthetic fractionation|post-photosynthetic fractionation.