Leaf mass area predicts palisade structural properties linked to mesophyll conductance in balsam poplar (Populus balsamifera L.).

Milla-Moreno, E.A., Guy, R.D., McKown, A.D., and Soolanayakanahally, R.Y. (2016). "Leaf mass area predicts palisade structural properties linked to mesophyll conductance in balsam poplar (Populus balsamifera L.).", Botany. doi : 10.1139/cjb-2015-0219  Access to full text

Abstract

Modifications to leaf structural components that drive variation in leaf mass per area (LMA) may substantially impact leaf physiology by changing how easily CO<sub>2</sub> diffuses through intercellular air space to carboxylation sites in mesophyll tissues. Mesophyll conductance (<i>g</i><sub>m</sub>) is inversely proportional to the total pathway length for CO<sub>2</sub>, including the structural resistances encountered. In balsam poplar (<i>Populus balsamifera</i>), <i>g</i><sub>m</sub> increases with latitude, paralleled by an increase in LMA. We investigated a <i>P. balsamifera</i> family (K4×C) with high variation in LMA for different characteristics (tissues, nitrogen content, ultrastructural attributes). We interpreted trait variability using a developmental scale quantified by the Leaf Plastochron Index (LPI). Developmental age significantly affected LMA, but those effects were lost at LPI≥6. We outlined contributions of anatomical components to LMA and found palisade mesophyll properties were the primary drivers of variation in LMA within mature leaves (LPI≥6). Using anatomical data, we derived components corresponding to structural resistances for <i>g</i><sub>m</sub>. Perimeters of palisade cells and surface area of palisade exposed to intercellular air space, which may strongly influence CO<sub>2</sub> diffusion, were correlated to LMA. Variation in LMA is positively related to differences in structural features expected to increase the conductance to CO<sub>2</sub> diffusion within palisade mesophyll.

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