Spatial heterogeneity in stomatal features during leaf elongation: an analysis using Rosa hybrida.

Area of Science:

• Plant physiology
• Plant anatomy
• Ecology

Background:

• Within-leaf variation in stomatal traits complicates whole-leaf gas exchange estimations.
• Stomatal conductance (gs) is a key determinant of plant water use and carbon uptake.
• Leaf development involves complex processes of stomatal initiation and growth.

Purpose of the Study:

• To investigate the patterns of stomatal initiation and growth during leaf expansion in Rosa hybrida.
• To quantify within-leaf heterogeneity in stomatal traits and stomatal conductance (gs) at different developmental stages and relative air humidity (RH) conditions.
• To determine the factors contributing to stomatal trait variation within a leaf.

Main Methods:

• Examined stomatal initiation and density across leaf development stages (percentages of full leaflet elongation - FLE).
• Estimated stomatal conductance (gs) in mature leaves under varying relative air humidity (RH).
• Analyzed the contribution of stomatal and epidermal cell differentiation to heterogeneity.

Main Results:

• Over 80% of stomata initiated between 33% and 67% FLE; stomatal growth occurred later.
• Significant within-leaf variation in gs (up to 40%) was observed in mature leaves.
• Elevated RH increased stomatal and pore dimensions but did not affect trait variation, except for pore aperture and gs.

Conclusions:

• Stomatal trait heterogeneity is influenced by leaf developmental stage and environmental conditions.
• Sampling strategies for stomatal traits must account for leaf development and evaporative demand.
• Understanding within-leaf variation is essential for accurate modeling of plant physiological responses.