Dynamics of stomatal patches for a single surface of Xanthium strumarium L. leaves observed with fluorescence and thermal images

Abstract

Fluorescence and thermal imaging were used to examine the dynamics of stomatal patches for a single surface of Xanthium strumarium L. leaves following a decrease in ambient humidity. Patches were not observed in all experiments, and in many experiments the patches were shortlived. In some experiments, however, patches persisted for many hours and showed complex temporal and spatial patterns. Rapidly sampled fluorescence images showed that the measurable variations of these patches were sufficiently slow to be captured by fluorescence images taken at 3-min intervals using a saturating flash of light. Stomatal patchiness with saturating flashes of light was not demonstrably different from that without saturating flashes of light, suggesting that the regular flashes of light did not directly cause the phenomenon. Comparison of simultaneous fluorescence and thermal images showed that the fluorescence patterns were largely the result of stomatal conductance patterns, and both thermal and fluorescence images showed patches of stomatal conductance that propagated coherently across the leaf surface. These nondispersing patches often crossed a given region of the leaf repeatedly at regular intervals, resulting in oscillations in stomatal conductance for that region. The existence of these coherently propagating structures has implications for the mechanisms that cause patchy stomatal behaviour as well as for the physiological ramifications of this phenomenon.

Evidence for Involvement of Photosynthetic Processes in the Stomatal Response to CO2

“…Gas-exchange data were recorded every 10 s, and fluorescence and thermal images were captured every 3 min. The details of the methods for fluorescence and thermal images have been described previously (West et al, 2005).…”

“…Gasexchange measurements were made using a standard, single-pass gas-exchange system that has also been described previously (West et al, 2005). For all experiments, leaf temperature was maintained at 25°C 6 0.2°C by changing air temperature, and the water vapor mole fraction gradient between the leaf and air was maintained at 15 mmol mol 21 by changing the mole fraction of water in the chamber air.…”

“…Cocklebur (Xanthium strumarium) plants were grown in a controlledenvironment greenhouse as described previously (West et al, 2005). Gasexchange measurements were made using a standard, single-pass gas-exchange system that has also been described previously (West et al, 2005).…”

Imaging of Chlorophyll a Fluorescence: A Tool to Study Abiotic Stress in Plants

“…This technique has been widely applied in the past during induction of photosynthesis (Bro et al, 1996;Oxborough & Baker, 1997), with changes in carbohydrate translocation (Meng et al, 2001), in response to drought (Meyer & Genty, 1999;West et al, 2005), chilling (Hogewoning & Harbinson, 2007), ozone pollution (Guidi et al, 2007;Guidi & Degl'Innocenti, 2008;Leipner et al, 2001), wounding (Quilliam et al, 2006), high light (Zuluaga et al, 2008) and infection with fungi (Guidi et al, 2007;Meyer et al, 2001;Scharte et al, 2005;Scholes & Rolfe, 1996;Schwarbrick et al, 2006) or virus (Perez-Bueno et al, 2006). With Chl fluorescence imaging is possible to detect an analysis of stress-induced changes in fluorescence emission at very early stage of stress.…”

Localization of Mechanisms Involved in Hydropassive and Hydroactive Stomatal Responses of Sambucus nigra to Dry Air

“…The phenomenon of stomatal patchiness also helps to pin down the spatial scale of transpiration-sensing mechanisms because it relies on locally coordinated actions of stomata. Thermal imaging and imaging of chlorophyll fluorescence, which is taken as a measure of CO 2 supply to the leaf and corresponds to stomatal opening, suggests that stomata inside an areole may behave similarly (West et al, 2005). This could point to a distributed sensing mechanism, which coordinates neighboring stomata.…”