Palisade cell geometry in relation to leaf optical and photosynthetic properties in Viburnum.

The optical properties of lobed palisade mesophyll cells remain poorly understood despite their presence in diverse taxa and the critical role of the palisade layer in leaf-light interactions and carbon assimilation. Using microcomputed tomography, 3D ray tracing simulations, and physiological experiments, we tested the interactions among palisade cell geometry, chloroplast localization, light directional quality, and leaf optical and photosynthetic performance in the model taxon Viburnum. Simulations showed that lobed cells shifted between absorptance- and transmittance-dominated states depending on chloroplast localization, irrespective of light directional quality.

Desiccation of the leaf mesophyll and its implications for CO diffusion and light processing.

Leaves balance CO and radiative absorption while maintaining water transport to maximise photosynthesis. Related species with contrasting leaf anatomy can provide insights into inherent and stress-induced links between structure and function for commonly measured leaf traits for important crops. We used two walnut species with contrasting mesophyll anatomy to evaluate these integrated exchange processes under non-stressed and drought conditions using a combination of light microscopy, X-ray microCT, gas exchange, hydraulic conductance, and chlorophyll distribution profiles through leaves.

Structural organization of the spongy mesophyll.

Many plant leaves have two layers of photosynthetic tissue: the palisade and spongy mesophyll. Whereas palisade mesophyll consists of tightly packed columnar cells, the structure of spongy mesophyll is not well characterized and often treated as a random assemblage of irregularly shaped cells. Using micro-computed tomography imaging, topological analysis, and a comparative physiological framework, we examined the structure of the spongy mesophyll in 40 species from 30 genera with laminar leaves and reticulate venation.

The Spatial Distribution of Chlorophyll in Leaves.

Measuring and modeling the spatial distribution of chlorophyll within the leaf is critical for understanding the relationship between leaf structure and carbon assimilation, for defining the relative investments in leaf tissues from the perspective of leaf economics theory, and for the emerging application of in silico carbon assimilation models. Yet, spatially resolved leaf chlorophyll distribution data are limited. Here, we used epi-illumination fluorescence microscopy to estimate relative chlorophyll concentration as a function of mesophyll depth for 57 plant taxa.