Ontogenetic Patterns of CO2 Exchange of Quercus rubra L. Leaves During Three Flushes of Shoot Growth I. Median Flush Leaves
Abstract:Oak (Quercus) seedlings exhibit a pattern of shoot growth known to place demands on carbohydrate and nutrient reserves. This study was designed to determine ontogenetic patterns in CO2 exchange properties of red oak leaves, and to determine if individual leaf CO2 exchange rates (CER) increase in response to the assimilate demand placed on a seedling during flushing. Northern red oak (Q. rubra L.) seedlings were grown in environments favorable for multiple flushes of shoot growth. Measurements of CER on single, attached, median leaves from each flush were made over a range of photosynthetic photon flux densities on plants at nine stages of seedling development through three flushes of growth. Carbon dioxide exchange rate of red oak leaves increased during leaf development up to and beyond full leaf expansion before decreasing --an unusual pattern of photosynthesis during leaf ontogeny. Furthermore, first- and second-flush leaf CER initially decreased and then increased in conjunction with the third flush of shoot growth. These patterns indicate that red oak leaves have a capacity for CER adjustment in response to increased sink demand. For. Sci. 34(1):55-68.
Document Type: Journal Article
Affiliations: Assistant Professor, Department of Forest Resources, College of Forestry, University of Minnesota, St. Paul MN 55108 (presently Assistant Professor, Auburn University, Auburn, AL 36849)
Publication date: March 1, 1988
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