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Pressure infiltration of water into a leaf via the stomatal pores can be used to quickly determine whether all stomata are open, or as recently described for several mesophytic and xerophytic species, whether there is a non-homogeneous distribution of stomatal opening (stomatal patchiness) on the leaf surface. Information about this phenomenon is important(More)
A multispecies canopy photosynthesis simulation model was used to examine the importance of canopy structure in influencing light interception and carbon gain in mixed and pure stands of wheat (Triticum aestivum L.) and wild oat (Avena fatua L.), a common weedy competitor of wheat. In the mixtures, the fraction of the simulated canopy photosynthesis(More)
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(More)
Strong evidence for the occurrence of pronounced stomatal patchiness in needles of Picea abies (L.) Karst. and Abies alba Mill. was found using various indirect methods. Anatomical investigations revealed a septate leaf anatomy for both species, a phenomenon expected if a patchy distribution of stomatal aperture is present. Calculation of some(More)
Arbuscular mycorrhizal fungi (AMF) may serve as an effective substitute for root surface. As mycorrhizal benefits are related to nutrient availability, the trade-off between carbon investments into AMF versus roots may drive competitive interactions. We studied competitive interactions between mycorrhizal and non-mycorrhizal individuals of Hieracium(More)
The carbon-dioxide response of photosynthesis of leaves of Quercus suber, a sclerophyllous species of the European Mediterranean region, was studied as a function of time of day at the end of the summer dry season in the natural habitat. To examine the response experimentally, a “standard” time course for temperature and humidity, which resembled natural(More)
At midday during hot and dry summer days under natural conditions, stomata of Mediterranean sclerophyllous shrubs usually close and leaf gas exchange rates are depressed. In addition to an influence related to plant water status the extent of this depression as well as the degree of recovery in the afternoon depends on degree of atmospheric stress:(More)
Gas exchange characteristics in leaves of the sclerophyll shrub Quercus coccifera were studied in the natural habitat in Portugal during spring and during the summer dry period. Compared to other sclerophyll species growing at the same site, photosynthesis in leaves of Quercus coccifera was less affected by water stress. Moderate water stress after six(More)
Photosynthetic performance of several needle age classes of Norway spruce trees [Picea abies (L.) Karst.] in highly SO2-polluted and heavily damaged forest sites was measured at two different locations in the Ore Mountains (Erzgebirge, Krusne Hory) during early summer. The carboxylation efficiency showed a dramatic drop from current-year's needles to(More)
The hypothesis that the frequently observed shedding of older needle age classes in stands of Norway spruce suffering from atmospheric pollutants has minimal effect on photosynthetic primary production was assessed. Using structural parameters of young Norway spruce [Picea abies (L.) Karst.] trees, an existing 3-dimensional canopy photosynthesis model was(More)