Abstract
During fall leaf senescence in deciduous species, photosynthesis nears completion due to chlorophyll breakdown and re-assimilation. However, several other processes such as leaf nutrient uptake, re-translocation, and storage, or tissue dehydration to avoid frost damage, may be important and dependent upon stomatal opening. We report here on measured changes in photosynthesis (A), leaf conductance to water vapor (g), and WUE (estimated by A/g) in three deciduous tree species (Acer saccharum, Cornus florida, and Ginkgo biloba) during the weeks of leaf senescence preceding abscission. Substantial decreases in A of 60 up to 80% were not matched quantitatively by similar declines in g (40 to 70%), resulting in corresponding decreases in WUE (estimated by A/g) from near 50% to over 300% among the three species. This shift to a lower WUE may reflect adaptive value in maintaining a higher g relative to A during the fall leaf senescence period.
Highlights
Hypotheses about the adaptive advantages of leaf color change during fall senescence have been proposed,[1] yet no study to our knowledge has focused on the A, g, and WUE relationship during this period that may last for weeks
The purpose of our study was to document changes in A, g, Ci, and WUE during fall leaf senescence in three deciduous tree species and, especially, the possibility that stomatal closure lagged behind declines in net photosynthesis
2013 Licensee PAGEPress srl, Italy International Journal of Plant Biology 2013; 4:e7 doi:10.4081/pb.2013.e7
Summary
Hypotheses about the adaptive advantages of leaf color change during fall senescence have been proposed,[1] yet no study to our knowledge has focused on the A, g, and WUE relationship during this period that may last for weeks. The purpose of our study was to document changes in A, g, Ci, and WUE during fall leaf senescence in three deciduous tree species and, especially, the possibility that stomatal closure lagged behind declines in net photosynthesis. Speculation about the adaptive significance of these changes is presented
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