Into the Spongy-Verse: Structural Differences between Leaf and Flower Mesophyll.

Area of Science:

• Plant anatomy
• Plant physiology
• Comparative biology

Background:

• Mesophyll tissue is crucial for carbon fixation in leaves.
• Mesophyll tissue is also found in floral perianths, offering a model to study structure-metabolism links.
• Differences in tissue structure may relate to metabolic variations between organs.

Purpose of the Study:

• To compare the mesophyll tissue structure of leaves and flower perianths across six species.
• To investigate the relationship between mesophyll cell shape, porosity, and intercellular airspace conductance.
• To understand how structural differences in mesophyll tissue relate to organ function and biomass investment.

Main Methods:

• High-resolution X-ray computed microtomography (microCT) imaging was used to analyze mesophyll tissue structure.
• Quantitative comparisons of stomatal density, vein density, and mesophyll porosity were performed.
• Intercellular airspace conductance was modeled based on tissue structural parameters.

Main Results:

• Flowers exhibited significantly lower stomatal and vein densities compared to leaves.
• Mesophyll porosity was significantly higher in flowers than in leaves.
• Higher mesophyll porosity in flowers correlated with more aspherical mesophyll cells.
• Despite structural differences, modeled intercellular airspace conductance did not significantly differ between leaf and flower mesophyll.

Conclusions:

• Leaf and flower mesophyll tissues display distinct structural characteristics, including cell shape and porosity.
• These structural variations may contribute to flowers being more biomass-efficient per unit surface area.
• The findings highlight significant internal tissue differences beyond stomatal and vein densities between reproductive and vegetative organs.