CO_(2)浓度和土壤含水量对植物个体尺度短期水分利用效率的影响

Effects of CO_(2) concentration and soil water content on short-term water-use efficiency at whole-plant level

分析植物个体短期水分利用效率(WUE_(p))对CO_(2)浓度(C_(a))和土壤含水量(SWC)的响应,可提高对气候变化下个体生存策略的认识。本研究以侧柏幼树为对象,在模拟气候箱中进行培养试验,设400(C_(400))、600(C_(600))和800μmol·mol^(-1)CO_(2)(C_(800))浓度处理和35%~45%田间持水量(FC)、50%~60%FC、60%~70%FC、70%~80%FC、95%~100%FC土壤含水量处理,共15个处理。WUE_(p)对C_(a)和SWC的响应用包裹式茎流计、称重法结合静态同化箱测定。结果表明:个体日间(0.12~1.87 mol·h^(-1))和夜间蒸腾速率(0.01~0.16 mol·h^(-1))均在C_(400)×70%~80%FC时达到最大值,个体日间净光合速率(2.12~22.10 mmol·h^(-1))在C_(800)×70%~80%FC时达到最大值,而个体夜间呼吸速率(0.84~4.41 mmol·h^(-1))随SWC的增加而增加,随C_(a)的增加而减小,在C_(400)×95%~100%FC时达到最大值。WUE_(p)(5.37~24.35 mmol·mol^(-1))在C_(800)×50%~60%FC时达到最大值,表明高C_(a)和干旱条件下,植物个体可通过生理可塑性调整,利用较少的水分固定更多的碳;此外,当个体间形态特征差异较小时,叶片瞬时水分利用效率可以较好地指示WUEP的变化。

Uncovering the variations of short-term water-use efficiency(WUE_(p)) at whole-plant level in response to CO_(2) concentration(C_(a)) and soil water content(SWC) can improve the understanding of plant survival strategies under climate change. In this study, Platycladus orientalis saplings were cultured in simulated climate chambers.There were totally 15 treatments, including C_(a) of 400(C_(400)), 600(C_(600)) and 800(C_(800)) μmol·mol^(-1) and SWC of 35%-45% field water holding capacity(FC), 50%-60%FC, 60%-70%FC, 70%-80%FC and 95%-100%FC. The WUE_(p) was measured by mini-lysimeters, weighting method, and static assimilation chamber. The results showed that both daytime(0.12-1.87 mol·h^(-1)) and nighttime transpiration rates(0.01-0.16 mol·h^(-1)) at whole-plant level reached the maximum at C_(400)×70%-80%FC, while the whole-plant daytime net photosynthetic rate(2.12-22.10 mmol·h^(-1)) reached the maximum at C_(800)×70%-80%FC. In contrast, nighttime respiration rate(0.84-4.41 mmol·h^(-1)) increased with increasing SWC, but decreased with increasing of C_(a), reaching the maximum at C_(400)×95%-100%FC. For WUE_(p)(5.37-24.35 mmol·mol^(-1)), it reached the maximum at C_(800)×50%-60%FC, indicating that plants could use less water and fixed more carbon by adjusting adaptation strategies under high C_(a) and drought conditions. In addition, leaf instantaneous water-use efficiency was a good predictor of WUEP when the canopy structure was similar.