Diurnal Courses of Stomatal Resistance and Transpiration of Wild and Cultivated Mediterranean Perennials at the End of the Summer Dry Season in Portugal
1982; Elsevier BV; Volume: 172; Issue: 2 Linguagem: Inglês
10.1016/s0367-2530(17)31323-3
ISSN1618-0585
AutoresR. Lösch, John Tenhunen, O. L. Lange, J. S. Pereira,
Tópico(s)Plant Physiology and Cultivation Studies
ResumoDaily time courses of leaf diffusion resistance, transpiration rate, for leaf environmental variables (measured with a steady-state porometer) and of xylem water potential (measured with a pressure chamber) were obtained for evergreen sclerophylls and cultivated Mediterranean plants growing at the Quinta São Pedro Research Station in Sobreda, south of Lisbon, Portugal. Leaves of the macchia plants Arbutus unedo, Myrtus communis, and Smilarx aspera as well as leaves of the cultivated tree Oastanea sativa exhibited a strong midday depression of gas exchange. Quercus suber and Quercus coccifera plants reduced their leaf water loss under hot and dry conditions less. Transpirational water loss was high from leaves of Ficus carica, well watered Nerium oleander, and Eriobotrya japonica. The response of plants to environmental conditions during the summer period and after the first fall rains is compared. In the case of Arbutus unedo the measurements continued from the summer dry period on into the winter, with mild and wet weather conditions. Initially the plot of transpiration rate as a function of time for Arbutus unedo was two-peaked due to midday stomatal closure. In the fall, midday closure was less evident and it disappeared entirely in December. The daily course of transpiration rate against time became dome shaped. The ecological importance of the species-specific behavior is discussed and interpreted partly in terms of morphological and anatomical features.
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