Journal Article

Patchy stomatal behavior during midday depression of leaf CO<sub>2</sub> exchange in tropical trees

Mai Kamakura, Yoshiko Kosugi, Satoru Takanashi, Kazuho Matsumoto, Motonori Okumura and Elizabeth Philip

Edited by Guillermo Goldstein

in Tree Physiology

Volume 31, issue 2, pages 160-168
Published in print February 2011 | ISSN: 0829-318X
Published online March 2011 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/tpq102
Patchy stomatal behavior during midday depression of leaf CO2 exchange in tropical trees

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We investigated effects of heterogeneous stomatal behavior on diurnal patterns of leaf gas exchange in 10 tree species. Observations were made in middle and upper canopy layers of potted tropical rainforest trees in a nursery at the Forest Research Institute Malaysia. Measurements were taken from 29 January to 3 February 2010. We measured in situ diurnal changes in net photosynthetic rate and stomatal conductance in three leaves of each species under natural light. In both top-canopy and sub-canopy species, midday depression of net assimilation rate occurred in late morning. Numerical analysis showed that patchy bimodal stomatal behavior occurred only during midday depression, suggesting that the distribution pattern of stomatal apertures (either uniform or non-uniform stomatal behavior) varies flexibly within single days. Direct observation of stomatal aperture using Suzuki's Universal Micro-Printing (SUMP) method demonstrated midday patchy stomatal closure that fits a bimodal pattern in Shorea leprosula Miq., Shorea macrantha Brandis. and Dipterocarpus tempehes V.Sl. Inhibition of net assimilation rate and stomatal conductance appears to be a response to changes in vapor pressure deficit (VPD). Variable stomatal closure with increasing VPD is a mechanism used by a range of species to prevent excess water loss from leaves through evapotranspiration (viz., inhibition of midday leaf gas exchange). Bimodal stomatal closure may occur among adjacent stomata within a single patch, rather than among patches on a single leaf. Our results suggest the occurrence of patches at several scales within single leaves. Further analysis should consider variable spatial scales in heterogeneous stomatal behavior between and within patches and within single leaves.

Keywords: heterobaric leaf; net assimilation rate; stomatal aperture distribution; stomatal conductance; vapor pressure deficit

Journal Article.  4136 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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