Leaf water content and palisade cell size.
The palisade cell sizes in leaves of Eucalyptus pauciflora were estimated in paradermal sections of cryo-fixed leaves imaged in the cryo-scanning electron microscope, as a quantity called the cell area fraction (CAF). Cell sizes were measured in detached leaves as a function of leaf water content, in intact leaves in the field during a day"s transpiration as a function of balance pressure of adjacent leaves, and on leaf disks equilibrated with air of relative humidities from 100 to 58%. Values of CAF ranged from 0.82 at saturation to approx. 0.3 in leaves dried to a relative water content (RWC) of 0.5, and in the field to approx. 0.58 at 15 bar (1.5 MPa) balance pressure. At a CAF of 0.58, the moisture content of the cell walls is in equilibrium with air at 90% relative humidity, which is the estimated relative humidity in the intercellular spaces. It is shown that at this moisture content, the cell walls could be exerting a pressure of approx. 50 bar on the cell contents.
Ecosystem Dynamics Group, Research School of Biological Sciences, Australian National University, Canberra, ACT 0200, Australia. martin.canny@anu.edu.au
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D048429:Cell Size; D002734:Chlorophyll / Q000378:metabolism; D020285:Cryoelectron Microscopy; D004579:Electron Transport / Q000502:physiology; D005052:Eucalyptus / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D006813:Humidity; D018515:Plant Leaves / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D014867:Water / Q000378:metabolism*
D014867:Water; D002734:Chlorophyll