Genotypically Identifying Wheat Mesophyll Conductance Regulation under Progressive Drought Stress

Area of Science:

• Plant Physiology
• Crop Science
• Photosynthesis Research

Background:

• Drought stress significantly impacts plant photosynthesis by constraining CO2 diffusion.
• Leaf mesophyll conductance for CO2 (gm) plays a vital role in photosynthesis and water use efficiency (WUE) under water-limited conditions.
• Understanding genotypic variation in gm responses to drought is crucial for improving crop resilience.

Purpose of the Study:

• To investigate the responses of leaf mesophyll conductance (gm) in four winter wheat genotypes under long-term progressive drought.
• To analyze genotypic variability in stomatal and non-stomatal limitations of net CO2 assimilation rate (AN) during drought.
• To determine the relationship between gm, stomatal conductance (gs), and photosynthetic efficiency under drought stress.

Main Methods:

• Gas-exchange measurements were used to assess AN, gs, and gm in winter wheat leaves.
• Long-term progressive drought was imposed on four different wheat genotypes.
• Variability in genotypic responses to drought was analyzed, considering both stomatal and non-stomatal factors.

Main Results:

• Progressive drought increased leaf diffusion resistance, decreasing AN, gm, and gs.
• Reduced gm led to the inhibition of carboxylation efficiency (Vcmax).
• A strong positive correlation between gm and gs was observed, suggesting co-regulation under drought.
• Non-stomatal limitations became more dominant than stomatal limitations in severely stressed plants.

Conclusions:

• Mesophyll conductance (gm) is a critical parameter influencing photosynthesis and WUE under drought in winter wheat.
• gm is a potential selection mechanism for enhancing diffusional properties and carbon assimilation in C3 plants during drought.
• Targeting gm can lead to improved photosynthetic performance and drought tolerance at the whole-plant level.