Stomatal patchiness in evergreen sclerophylls

Wolfram Beyschlag, Bielefeld University, Germany – (Wuerzburg Univ. (Germany). Lehrstuhl für Botanik 2)

 

Stomatal patchiness in Mediterranean evergreen sclerophylls : Phenomenology and consequences for the interpretation of the midday depression in photosynthesis and transpiration.

by Beyschlag W., Pfanz H., Ryel R. J. (1992)

Julius-von-Sachs Institut für Biowissenschaften, Lehrstuhl Botanik II Universität Würzburg, Mittlerer Dallenbergweg 64, W-8700, Würzburg, Germany.

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in Planta. 1992 Jul;187(4):546-53. doi: 10.1007/BF00199976. – PMID: 24178151 –

https://www.ncbi.nlm.nih.gov/pubmed/24178151

Abstract

Midday depression of net photosynthesis and transpiration in the Mediterranean sclerophylls Arbutus unedo L. and Quercus suber L. occurs with a depression of mesophyll photosynthetic activity as indicated by calculated carboxylation efficiency (CE) and constant diurnal calculated leaf intercellular partial pressure of CO2 (Ci).

This work examines the hypothesis that this midday depression can be explained by the distribution of patches of either wide-open or closed stomata on the leaf surface, independent of a coupling mechanism between stomata and mesophyll that results in a midday depression of photosynthetic activity of the mesophyll.

Pressure infiltration of four liquids differing in their surface tension was used as a method to show the occurrence of stomatal patchiness and to determine the status of stomatal aperture within the patches.

Liquids were selected such that the threshold leaf conductance necessary for infiltration through the stomatal pores covered the expected diurnal range of calculated leaf conductance (g) for these species. Infiltration experiments were carried out with leaves of potted plants under simulated Mediterranean summer conditions in a growth chamber.

For all four liquids, leaves of both species were found to be fully infiltratable in the morning and in the late afternoon while during the periods leading up to and away from midday the leaves showed a pronounced patchy distribution of infiltratable and non-infiltratable areas.

Similar linear relationships between the amount of liquid infiltrated and g (measured by porometry prior to detachment and infiltration) for all liquids clearly revealed the existence of pneumatically isolated patches containing only wide-open or closed stomata.

The good correspondence between the midday depression of CE, calculated under the assumption of no stomatal patchiness, and the diurnal changes in non-infiltratable leaf area strongly indicates that the apparent reduction in mesophyll activity results from assuming no stomatal patchiness.

It is suggested that simultaneous responses of stomata and mesophyll activity reported for other species may also be attributed to the occurrence of stomatal patchiness.

In Quercus coccifera L., where the lack of constant diurnal calculated Ci and major depression of measured CE at noontime indicates different stomatal behavior, non-linear and dissimilar relationships between g and the infiltratable quantities of the four liquids were found. This indicates a wide distribution of stomatal aperture on the leaf surface rather than only wide-open or closed stomata.

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 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 patchiness in sclerophylls

STOMATAL PATCHINESS IN MEDITERRANEAN EVERGREEN SCLEROPHYLLS – PHENOMENOLOGY AND CONSEQUENCES FOR THE INTERPRETATION OF THE MIDDAY DEPRESSION IN PHOTOSYNTHESIS AND TRANSPIRATION

by Beyschlag W., Pfanz H., Ryel R. J. (1992)

in Planta187: 546–553.

Abstract

Midday depression of net photosynthesis and transpiration in the Mediterranean sclerophylls Arbutus unedo L. and Quercus suber L. occurs with a depression of mesophyll photosynthetic activity as indicated by calculated carboxylation efficiency (CE) and constant diurnal calculated leaf intercellular partial pressure of CO2 (C(i)). This work examines the hypothesis that this midday depression can be explained by the distribution of patches of either wide-open or closed stomata on the leaf surface, independent of a coupling mechanism between stomata and mesophyll that results in a midday depression of photosynthetic activity of the mesophyll. Pressure infiltration of four liquids differing in their surface tension was used as a method to show the occurrence of stomatal patchiness and to determine the status of stomatal aperture within the patches. Liquids were selected such that the threshold leaf conductance necessary for infiltration through the stomatal pores covered the expected diurnal range of calculated leaf conductance (g) for these species. Infiltration experiments were carried out with leaves of potted plants under simulated Mediterranean summer conditions in a growth chamber. For all four liquids, leaves of both species were found to be fully infiltratable in the morning and in the late afternoon while during the periods leading up to and away from midday the leaves showed a pronounced patchy distribution of infiltratable and non-infiltratable areas. Similar linear relationships between the amount of liquid infiltrated and g (measured by porometry prior to detachment and infiltration) for all liquids clearly revealed the existence of pneumatically isolated patches containing only wide-open or closed stomata. The good correspondence between the midday depression of CE, calculated under the assumption of no stomatal patchiness, and the diurnal changes in non-infiltratable leaf area strongly indicates that the apparent reduction in mesophyll activity results from assuming no stomatal patchiness. It is suggested that simultaneous responses of stomata and mesophyll activity reported for other species may also be attributed to the occurrence of stomatal patchiness. In Quercus coccifera L., where the lack of constant diurnal calculated C(i) and major depression of measured CE at noontime indicates different stomatal behavior, nonlinear and dissimilar relationships between g and the infiltratable quantities of the four liquids were found. This indicates a wide distribution of stomatal aperture on the leaf surface rather than only wide-open or closed stomata.

See the text: Web of Science