Simulations and observations of patchy stomatal behavior in leaves of Quercus crispula, a cool-temperate deciduous broad-leaved tree species.
We investigated the occurrence of patchy stomatal behavior in leaves of saplings and a forest canopy tree of Quercus crispula Blume. Through a combination of leaf gas-exchange measurements and numerical simulation, we detected patterns of stomatal closure (either uniform or patchy bimodal) coupled with depression of net assimilation rate (A). There was a clear inhibition of A associated with stomatal closure in leaves of Q. crispula during the day, but the magnitude of inhibition varied among days and growing conditions. Comparisons of observed and simulated A values for both saplings and the canopy tree identified patterns of stomatal behavior that shifted flexibly between uniform and patchy frequency distributions depending on environmental conditions. Bimodal stomatal closure explained severe depression of A in saplings under conditions of relatively high leaf temperature and vapor pressure deficit. Model simulations of A depression through bimodal stomatal closure were corroborated by direct observations of stomatal aperture distribution using Suzuki's Micro-Printing method; these demonstrated that there was a real bimodal frequency distribution of stomatal apertures. Although there was a heterogeneous distribution of stomatal apertures both within and among patches, induction of heterogeneity in intercellular CO₂ concentration among patches, and hence severe depression of A, resulted only from bimodal stomatal closure among patches (rather than within patches).
KYOUSEI Science Center for Life and Nature, Nara Women's University, Kita-uoya Higashimachi, Nara 630-8506, Japan. mkamakura@cc.nara-wu.ac.jp
Mai
M
Kamakura
Yoshiko
Y
Kosugi
Kanako
K
Muramatsu
Hiroyuki
H
Muraoka
D002245:Carbon Dioxide / Q000378:metabolism*; D002940:Circadian Rhythm; D055907:Climatic Processes; D003080:Cold Temperature; D004781:Environmental Exposure; D007564:Japan; D008962:Models, Theoretical; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism*; D054046:Plant Stomata / Q000378:metabolism*; D018526:Plant Transpiration; D029963:Quercus / Q000378:metabolism*; D055548:Vapor Pressure
D002245:Carbon Dioxide