土壤水分胁迫和大气CO2浓度对光合分馏及后光合分馏的影响

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(ΔC_a-leaf)和光合作用后叶片到枝条间的碳同位素分馏(ΔC_leaf-phlo)对土壤含水量(SWC)和大气CO₂浓度(C_a)的响应。结果表明: ΔC_a-leaf在SWC为田间持水量(FC)的95%～100%(95%～100%FC)且C_a为400 μmol·mol^-1时达到最大值(13.06‰),在SWC为35%～45%FC且C_a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ΔC_a-leaf呈显著线性正相关,相关系数分别为0.43和0.44;而ΔC_leaf-phlo并未受到SWC和C_a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。

Effects of soil water stress and atmospheric CO2 concentration on photosynthetic and post-photosynthetic fractionation

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 (ΔC_a-leaf) and leaf-twig discrimination during post-photosynthesis (ΔC_leaf-phlo), in response to changes of soil water content (SWC) and atmospheric CO₂ concentration (C_a). The results showed that ΔC_a-leaf reached a maximum of 13.06‰ at 95%-100% field water-holding capacity (FC) and C_a 400 μmol·mol^-1, and a minimum of 8.63‰ at 35%-45% FC and C_a 800 μmol·mol^-1. Both stomatal conductance and mesophyll cell conductance showed a significant linear positive correlation with ΔC_a-leaf, with a correlation coefficient of 0.43 and 0.44, respectively. ΔC_leaf-phlo was not affected by SWC and C_a. Our results provide mechanism of carbon isotopes fractionation and a theoretical basis for plant survival strategies in response to future climate change.