Coordinated stomatal, mesophyll, and biochemical functions in photosynthetic responses to heat and dryness

• 成果类型: Article
• 署名作者: Hu, Xingyu; Wong, Suan Chin; Farquhar, Graham D.
• 署名单位: Tsinghua University; Australian National University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2605032123
• 发表日期: 2026-05-12
• 页码: e2605032123
• 关键词: photosynthesis; temperature; leaf-to-air vapor pressure difference; CO2 diffusional limitation; biochemical limitation; chlorophyll fluorescence; temperature response; ELECTRON-TRANSPORT; INTERNAL CONDUCTANCE; rubisco activase; CO2 ASSIMILATION; quantum yield; gas-exchange; C-3 PLANTS; leaves

摘要

The intrinsic link between temperature and leaf-to-air vapor pressure difference (Delta e) complicates isolation of their individual effects on photosynthesis. Consequently, how CO2 diffusion changes under heat and high evaporative demand, particularly through mesophyll conductance (g(m)) responses, remains poorly understood. The conditions under which biochemical colimitation occurs, meaning Rubisco carboxylation and RuBP regeneration capacities match, are also unclear. To advance understanding of plant responses to climate change, we separated temperature and Delta e effects by holding Delta e at 1 and 2 kPa while varying leaf temperature (T-leaf) from 20 to 40 degrees C across five CO2 levels (150 to 800 mu mol mol(-1)) in cotton, sunflower, and dwarf bean. Gas exchange and chlorophyll fluorescence measurements showed that g(m) responses partly counteract increases in stomatal conductance to CO2 (g(sc)) at high temperatures and declines in g(sc) at elevated Delta e. Coordination between g(sc) and g(m) buffers effects of heat and dryness on CO2 diffusion and stabilizes chloroplast-to-ambient CO2 ratio (C-c/C-a) across measured T-leaf and Delta e ranges. C-c/C-a is more conservative with increasing T-leaf at C-a <= 400 mu mol mol(-1) than at elevated C-a. Across tested T-leaf and Delta e conditions, the transition from Rubisco carboxylation to RuBP regeneration limitation remains near C-a of 400 mu mol mol(-1), indicating that biochemical colimitation occurs near current atmospheric CO2 levels. Our findings reveal that plants alleviate diffusional limitations under heat and dryness through coordinated responses of g(sc) and g(m), and maintain biochemical colimitation over broad T-leaf and Delta e conditions to efficiently utilize Rubisco carboxylation and RuBP regeneration capacities at near-atmospheric CO2 levels.