Stomatal crypts may facilitate diffusion of CO2 to adaxial mesophyll cells in thick sclerophylls |
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Authors: | FOTEINI HASSIOTOU JOHN R EVANS MARTHA LUDWIG & ERIK J VENEKLAAS |
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Institution: | School of Plant Biology, Faculty of Natural and Agricultural Sciences and;School of Biomedical, Biomolecular and Chemical Sciences, Faculty of Life and Physical Sciences, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Australia and;Environmental Biology Group, Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra, ACT 0200, Australia |
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Abstract: | In some plants, stomata are exclusively located in epidermal depressions called crypts. It has been argued that crypts function to reduce transpiration; however, the occurrence of crypts in species from both arid and wet environments suggests that crypts may play another role. The genus Banksia was chosen to examine quantitative relationships between crypt morphology and leaf structural and physiological traits to gain insight into the functional significance of crypts. Crypt resistance to water vapour and CO2 diffusion was calculated by treating crypts as an additional boundary layer partially covering one leaf surface. Gas exchange measurements of polypropylene meshes confirmed the validity of this approach. Stomatal resistance was calculated as leaf resistance minus calculated crypt resistance. Stomata contributed significantly more than crypts to leaf resistance. Crypt depth increased and accounted for an increasing proportion of leaf resistance in species with greater leaf thickness and leaf dry mass per area. All Banksia species examined with leaves thicker than 0.6 mm had their stomata in deep crypts. We propose that crypts function to facilitate CO2 diffusion from the abaxial surface to adaxial palisade cells in thick leaves. This and other possible functions of stomatal crypts, including a role in water use, are discussed. |
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Keywords: | gas exchange leaf anatomy photosynthesis resistance sclerophylly stomatal encryption sunken stomata |
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