College of Science and Engineering, James Cook University, Cairns, Queensland 4879, Australia
Ecosystem Fluxes and Stable Isotope Research Group, Paul Scherrer Institute, 5232 Villigen, Switzerland.
Plant Physiol. 2019 Dec;181(4):1573-1586. doi: 10.1104/pp.19.00436. Epub 2019 Sep 27.
Stomata control the gas exchange of terrestrial plant leaves, and are therefore essential to plant growth and survival. We investigated gas exchange responses to vapor pressure deficit (VPD) in two gray poplar () lines: wild type and abscisic acid-insensitive () with functionally impaired stomata. Transpiration rate in increased linearly with VPD, up to about 2 kPa. Above this, sharply declining transpiration was followed by leaf death. In contrast, wild type showed a steady or slightly declining transpiration rate up to VPD of nearly 7 kPa, and fully recovered photosynthetic function afterward. There were marked differences in discrimination against CO (ΔC) and COO (ΔO) between and wild-type plants. The ΔC indicated that intercellular CO concentrations decreased with VPD in wild-type plants, but not in plants. The ΔO reflected progressive stomatal closure in wild type in response to increasing VPD; however, in , stomata remained open and oxygen atoms of CO continued to exchange with O enriched leaf water. Coupled measurements of ΔO and gas exchange were used to estimate intercellular vapor pressure, In wild-type leaves, there was no evidence of unsaturation of , even at VPD above 6 kPa. In leaves, approached 0.6 times saturation vapor pressure before the precipitous decline in transpiration rate. For wild type, a sensitive stomatal response to increasing VPD was pivotal in preventing unsaturation of In , after taking unsaturation into account, stomatal conductance increased with increasing VPD, consistent with a disabled active response of guard cell osmotic pressure.
气孔控制着陆生植物叶片的气体交换，因此对植物的生长和生存至关重要。我们研究了两种灰杨（）品系（野生型和脱落酸不敏感型）在蒸汽压亏缺（VPD）下的气体交换响应：气孔功能受损。增加，蒸腾速率呈线性增加，直到约 2 kPa。在此之上，蒸腾速率急剧下降，随后叶片死亡。相比之下，野生型表现出稳定或略有下降的蒸腾速率，直至 VPD 接近 7 kPa，之后光合作用功能完全恢复。与野生型植物相比，和野生型植物之间的 CO （ΔC）和 COO （ΔO）的歧视有明显差异。ΔC 表明，在野生型植物中，细胞间 CO 浓度随 VPD 降低，但在植物中没有。ΔO 反映了随着 VPD 的增加，野生型植物中气孔逐渐关闭；然而，在中，气孔仍然开放，CO 的氧原子继续与富含 O 的叶片水进行交换。用 ΔO 和气体交换的耦合测量来估计细胞间蒸汽压，在野生型叶片中，即使 VPD 高于 6 kPa，也没有证据表明不饱和。在叶片中，接近 0.6 倍饱和蒸气压，然后蒸腾速率急剧下降。对于野生型，对增加 VPD 的敏感气孔反应对于防止不饱和至关重要。在中，考虑到不饱和后，气孔导度随 VPD 的增加而增加，这与保卫细胞渗透压力的主动响应失活一致。
