Changes in photon flux can induce stomatal patchiness

 

 

by Eckstein J., Beyschlag W., Mott K. A., Ryel R. J. (1996)

Wolfram Beyschlag, Lehrstuhl für experimentelle Ökologie und Ökosystembiologie, Universitätsstraße 25, D-33615 Bielefeld, Germany.

in Plant, Cell & Environment 19(9): 1066-1074 – DOI: 10.1111/j.1365-3040.1996.tb00213.x

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3040.1996.tb00213.x/full

ABSTRACT

Images of chlorophyll fluorescence were used to detect the occurrence of stomatal patchiness in leaves from eight species under variable photon flux conditions. Pronounced stomatal patchiness was induced within 5–10 min after PFD was changed from intermediate (∼450 μmol quanta m⁻² s⁻¹) to low (∼150 μmol quanta m⁻² s⁻¹) levels. This effect was completely reversible by returning PFD to intermediate levels. The pattern of heterogeneous fluorescence for each leaf was usually similar during repeated applications of medium and low PFD. In three species, stomatal patchiness could only be induced in slightly water-stressed plants. Leaves of more severely water-stressed Xanthium strumarium plants in low air humidity exhibited oscillations in fluorescence that corresponded with oscillatory changes in leaf diffusion conductance for water vapour. Stomatal patchiness was also induced by illuminating dark-adapted leaves with low PFD (below 200–300 μmol quanta m⁻² s⁻¹). Infiltration of leaves with distilled water showed that heterogeneous chlorophyll fluorescence was caused by changes in stomatal apertures.

Stomatal patchiness

 

Towards a Causal Analysis of Stomatal Patchiness. The Role of Stomatal Size Variability and Hydrological Heterogeneity

by Beyschlag W.,

Eckstein J. (2001)

in Acta Oecologica, Vol. 22, No. 3, 2001, pp. 161-173. –

http://dx.doi.org/10.1016/S1146-609X(01)01110-9

Abstract

The induction of the well known and widespread phenomenon ‘stomatal patchiness’ has been attributed to a variety of potential causes: from low PPFD levels, all kinds of stress conditions to CO₂-changes and even fungal infections.

A mechanism which explains the occurrence of reproducible patterns of static (i.e. stable) stomatal patchiness at low PPFD levels is proposed. Further, experimental evidence is presented for the hypothesis that dynamic (i.e. not stable) stomatal patchiness is a consequence of heterogeneous water status in different parts of the leaf and can be induced by all ambient factors which cause such heterogeneities.

Stomatal patchiness in leaves

Photo credit: Google

Xanthium strumarium

Changes in photon flux can induce stomatal patchiness

by Eckstein J., Beyschlag W., Mott K. A., Ryel R. J. (1996)

in Plant, Cell and Environment19,1066–1074. 

CrossRef, Abstract, PDF(9071K), References,

Abstract

Images of chlorophyll fluorescence were used to detect the occurrence of stomatal patchiness in leaves from eight species under variable photon flux conditions.

Pronounced stomatal patchiness was induced within 5–10 min after PFD was changed from intermediate (∼450 μmol quanta m⁻² s⁻¹) to low (∼150 μmol quanta m⁻² s⁻¹) levels. This effect was completely reversible by returning PFD to intermediate levels.

The pattern of heterogeneous fluorescence for each leaf was usually similar during repeated applications of medium and low PFD. In three species, stomatal patchiness could only be induced in slightly water-stressed plants.

Leaves of more severely water-stressed Xanthium strumarium plants in low air humidity exhibited oscillations in fluorescence that corresponded with oscillatory changes in leaf diffusion conductance for water vapour.

Stomatal patchiness was also induced by illuminating dark-adapted leaves with low PFD (below 200–300 μmol quanta m⁻² s⁻¹).

Infiltration of leaves with distilled water showed that heterogeneous chlorophyll fluorescence was caused by changes in stomatal apertures.

Abstract: Wiley

Read the full article: Wiley

Stomatal turgor mechanism

Photo credit: JXB

Fig. 5.

Images of stoma 1 from the experiment shown in Fig. 4 during a peak of the oscillation (a) and in the closed state 6 min later (b). The time of observation is also marked by arrows in Fig. 4. The arrow in (a) points to the slightly open pore.

Stomatal oscillations at small apertures: indications for a fundamental insufficiency of stomatal feedback‐control inherent in the stomatal turgor mechanism

by Kaiser H., Kappen L. (2001)

in J. Exp. Bot. (2001) 52 (359):1303-1313. – doi:10.1093/jexbot/52.359.1303. 

Abstract

Continuous measurements of stomatal aperture simultaneously with gas exchange during periods of stomatal oscillations are reported for the first time. Measurements were performed in the field on attached leaves of undisturbed Sambucus nigra L. plants which were subjected to step‐wise increases of PPFD. Oscillations only occurred when stomatal apertures were small under high water vapour mole fraction difference between leaf and atmosphere (Δ_W). They consisted of periodically repeated opening movements transiently leading to very small apertures. Measurements of the area of the stomatal complex in parallel to the determination of aperture were used to record volume changes of guard cells even if stomata were closed. Stomatal opening upon a light stimulus required an antecedent guard cell swelling before a slit occurred. After opening of the slit the guard cells again began to shrink which, with some delay, led to complete closure. Opening and closing were rhythmically repeated. The time‐lag until initial opening was different for each individual stoma. This led to counteracting movements of closely adjacent stomata. The tendency to oscillate at small apertures is interpreted as being a failure of smoothly damped feedback regulation at the point of stomatal opening: Volume changes are ineffective for transpiration if stomata are still closed; however, at the point of initial opening transpiration rate rises steeply. This discontinuity together with the rather long time constants inherent in the stomatal turgor mechanism makes oscillatory overshooting responses likely if at high Δ_W the ‘nominal value’ of gas exchange demands a small aperture.

Read the full article: JXB