Starch dynamics and preferential pathways of starch degradation in mesophyll cells (left) and guard cells (right). Essential enzymes in each cell type are highlighted. Maltose and glucose (Glc) produced from starch breakdown in the chloroplast are exported to the cytosol via the maltose (MEX1) and Glc (GlcT) transporters, respectively (yellow cylinders, left). Question marks refer to enzymes and transporters whose involvement in the guard cell starch degradation pathway has not been experimentally verified.
Transitory starch metabolism in guard cells: unique features for a unique function.
by Santelia D., Lunn J. E. (2017)
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in Plant Physiol 174(2): 539–549 – DOI: https://doi.org/10.1104/pp.17.00211 –
http://www.plantphysiol.org/content/174/2/539
Abstract
This update focuses on the starch that accumulates in the guard cells that control stomatal pore size and thus the exchange of water vapor, CO2, and O2 between the leaf and the atmosphere.
Transitory starch in these cells plays a key role in determining the velocity of stomatal opening in the light.
This significantly differs from the transitory starch in the mesophyll leaves, which acts primarily as a carbohydrate reserve to sustain plant metabolism during the night.
We discuss how the unique function of transitory starch in guard cells is reflected in the timing of its deposition and mobilization, along with differences from mesophyll cells in the pathways and regulation of starch metabolism.
PLANT STOMATA ENCYCLOPEDIA 