Zhang Dalong, Du Qingjie, Sun Po, Lou Jie, Li Xiaotian, Li Qingming, Wei Min
College of Horticultural Science and Engineering, Shandong Agricultural University, Tai'an, China.
State Key Laboratory of Crop Biology, Tai'an, China.
Front Plant Sci. 2021 Nov 10;12:745110. doi: 10.3389/fpls.2021.745110. eCollection 2021.
The atmospheric vapour pressure deficit (VPD) has been demonstrated to be a significant environmental factor inducing plant water stress and affecting plant photosynthetic productivity. Despite this, the rate-limiting step for photosynthesis under varying VPD is still unclear. In the present study, tomato plants were cultivated under two contrasting VPD levels: high VPD (3-5 kPa) and low VPD (0.5-1.5 kPa). The effect of long-term acclimation on the short-term rapid VPD response was examined across VPD ranging from 0.5 to 4.5 kPa. Quantitative photosynthetic limitation analysis across the VPD range was performed by combining gas exchange and chlorophyll fluorescence. The potential role of abscisic acid (ABA) in mediating photosynthetic carbon dioxide (CO) uptake across a series of VPD was evaluated by physiological and transcriptomic analyses. The rate-limiting step for photosynthetic CO utilisation varied with VPD elevation in tomato plants. Under low VPD conditions, stomatal and mesophyll conductance was sufficiently high for CO transport. With VPD elevation, plant water stress was gradually pronounced and triggered rapid ABA biosynthesis. The contribution of stomatal and mesophyll limitation to photosynthesis gradually increased with an increase in the VPD. Consequently, the low CO availability inside chloroplasts substantially constrained photosynthesis under high VPD conditions. The foliar ABA content was negatively correlated with stomatal and mesophyll conductance for CO diffusion. Transcriptomic and physiological analyses revealed that ABA was potentially involved in mediating water transport and photosynthetic CO uptake in response to VPD variation. The present study provided new insights into the underlying mechanism of photosynthetic depression under high VPD stress.
大气蒸汽压亏缺（VPD）已被证明是诱导植物水分胁迫并影响植物光合生产力的一个重要环境因素。尽管如此，不同VPD条件下光合作用的限速步骤仍不清楚。在本研究中，番茄植株在两种对比鲜明的VPD水平下栽培：高VPD（3 - 5千帕）和低VPD（0.5 - 1.5千帕）。研究了长期驯化对0.5至4.5千帕VPD范围内短期快速VPD响应的影响。通过结合气体交换和叶绿素荧光对整个VPD范围进行了光合限制定量分析。通过生理和转录组分析评估了脱落酸（ABA）在介导一系列VPD条件下光合二氧化碳（CO₂）吸收中的潜在作用。番茄植株光合CO₂利用的限速步骤随VPD升高而变化。在低VPD条件下，气孔和叶肉导度足够高，有利于CO₂传输。随着VPD升高，植物水分胁迫逐渐加剧，并触发了快速的ABA生物合成。气孔和叶肉限制对光合作用的贡献随着VPD的增加而逐渐增加。因此，在高VPD条件下，叶绿体内部低CO₂可用性极大地限制了光合作用。叶片ABA含量与CO₂扩散的气孔和叶肉导度呈负相关。转录组和生理分析表明，ABA可能参与介导水分运输和光合CO₂吸收以响应VPD变化。本研究为高VPD胁迫下光合抑制的潜在机制提供了新的见解。
