Patchy stomatal behavior during midday depression of leaf CO2 exchange in tropical trees

Abstract

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.

Non-convergent transpiration and stomatal conductance response of a dominant desert species in central Asia to climate drivers at leaf, branch and whole plant scales

“…This showed that there were other factors affecting the heterogeneity of leaf behaviors within canopy besides climate drivers. The patchy stomatal behavior has been found among adjacent leaves and even in the same leaf Terashima, 1992;Mott and Buckley, 2000;Kamakura et al, 2011 , which is consistent with the different water use and stomatal pattern between leaf-and branch-scale found in this study. Many hypothesis including circadian rhythms Doughty et al 2006 , chemical signal Garcıá-Mata andLamattina, 2001 and hydraulic interactions Mott and Buckley, 2000 have been proposed but the underlying mechanism is still unclear.…”

Simulations and observations of patchy stomatal behavior in leaves of Quercus crispula, a cool-temperate deciduous broad-leaved tree species

“…Direct observation of stomatal aperture distributions using Suzuki's Universal Micro-Printing (SUMP) method showed a real patchy bimodal distribution of stomatal apertures during midday depression in leaves of mid-and upper-layers in tropical tree vegetation. Furthermore, there was a heterogeneous distribution of stomatal apertures among adjacent stomata rather than among compartments delimited by bundle sheath extensions (Kamakura et al 2011). By numerical analysis, we also found that patchy bimodal stomatal behavior occurs only during midday depression, suggesting that stomatal aperture distribution varies flexibly within single days.…”

“…Changes in pattern of stomatal behavior by day and growing condition Patchy stomatal closure occurs with midday depression of A in tree species with heterobaric leaves (Beyschlag and Pfanz 1990;Beyschlag et al 1992;Takanashi et al 2006;Kamakura et al 2011). We showed a clear inhibition of A coupled with stomatal closures in leaves of both saplings and a canopy tree of Q. crispula during the daytime hours on clear days (1 and 24 June in the nursery, and 2 August at the TKY site), but the magnitude of inhibition varied by day and growing conditions (Figs.…”

“…To determine real stomatal behavior distributions, we calculated the frequency distribution of stomatal apertures for single leaves from saplings and the canopy tree using the SUMP method (Kamakura et al 2011). Immediately following leaf gas exchange measurements, we made impressions of the surface of one of the three experimental leaves by fastening thin celluloid plate (2 cm in diameter, SUMP Laboratory, Tokyo, Japan) dissolved in amyl acetate to the abaxial leaf surface (the site at which gas exchange rate was measured).…”

“…Because uniform stomatal behavior is assumed in leaf gasexchange calculations based on the Farquhar-von Caemmerer-Berry model (von Caemmerer and Farquhar 1981;Warren et al 2003), the effect of patchy stomatal closure on depression of A may well have been underestimated. Although, the importance of patchy stomatal closure effects on leaf gas-exchange rates is recognized, only a few studies have evaluated the pattern of stomatal behavior (uniform or patchy bimodal) associated with A depression in tree leaves under natural conditions (Takanashi et al 2006;Kosugi et al 2009;Kamakura et al 2011).…”