Light-flecks cause non-uniform stomatal opening – studies with special emphasis on Fagus sylvatica L. |
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Authors: | M Küppers I Heiland H Schneider P J Neugebauer |
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Institution: | Institut für Botanik, Technische Universit?t Darmstadt Schnittspahnstrasse 10, D-64287 Darmstadt, Germany, DE Fraunhofer-Institut für Angewandte Graphische Datenverarbeitung, Wilhelminenstrasse 7 D-64287 Darmstadt, Germany, DE
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Abstract: | The appearance of stomatal patchiness in response to rapid (seconds) changes in light has been studied in European beech, Fagus sylvatica L., and, by comparison, in a further 17 different woody species from the understorey of a European beech forest, using a
simple water infiltration method. Water infiltrated areoles indicate open stomata. Since infiltration changes optical characteristics
of a leaf section it can be analysed by photography, computer-aided image analysis and by weighing. For F. sylvatica clear differences were found between infiltration of cotyledons (no patchy pattern) and any other leaf type. Despite identical
cultivation, leaves of the same type and age from different individual plants responded differently to application of 30 s
of light after darkness. In contrast, the patchiness patterns were very similar for leaves of the same type originating from
the same plant. Infiltration patterns after a light-fleck, observed on different leaves as a series of momentary clusters,
probably indicate waves of opening stomata moving across the leaf blade. During and after a 30 s light-fleck infiltration
increased and it continued to increase in the dark up to 10 min, indicating increasing stomatal opening over that period.
In general, shade leaves became more infiltrated (by weight) than half-shade or sun leaves, due to larger intercellular air
spaces. All species, without exception, showed patchy infiltration and, thus, non-uniform stomatal opening. Measuring leaf
gas exchange (as ”quasi-steady states” using a fast responding system) during photosynthetic induction resulted in very similar
CO2 responses of net photosynthesis (A/c
i) as in the true steady state, proving that, in shade and half-shade leaves, the presence of stomatal patchiness does not
necessarily affect the calculation of intercellular CO2 concentrations. Causes and consequences of stomatal patchiness are discussed.
Received: 18 November 1998 / Accepted: 1 July 1999 |
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Keywords: | Half-shade leaves Photosynthetic induction Shade leaves Stomatal patchiness Water infiltration method |
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