Effects of Defoliation in the Developing Leaf Zone on Young Populus X euramericana Plants. I. Photosynthetic Physiology, Growth, and Dry Weight Partitioning

Authors: Bassman, John H.; Dickmann, Donald I.

Source: Forest Science, Volume 28, Number 3, 1 September 1982 , pp. 599-612(14)

Publisher: Society of American Foresters

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Controlled-environment studies were used to test the effects of a single, partial defoliation on growth, dry weight partitioning, photosynthesis, and leaf conductance of young poplar plants. Rates of photosynthesis and leaf conductance were determined and biomass harvests made 24 hr, 3 weeks, and 5 weeks after defoliation in the developing leaf zone. Photosynthesis was calculated from uptake of a 20 s pulse of 14CO2 administered to a portion of a leaf by a portable gassing device. Leaf conductance was measured with a diffusion porometer. Insignificant differences in height and diameter growth were observed between control and defoliated plants, but the latter displayed reduced root dry weights. Defoliation stimulated a twofold increase in lateral branch development. Individual leaves developing subsequent to defoliation were up to 43 percent larger than complementary leaves on control plants. Leaves on defoliated plants had significantly higher rates of photosynthesis than complementary leaves on control plants. There was a stimulation of photosynthetic rates on mature leaves below the zone of defoliation within 24 hr of treatment. This effect continued up to 5 weeks. New leaves produced subsequent to defoliation were larger and had higher photosynthetic rates than new leaves on control plants. Leaf conductance was higher on defoliated plants and followed a pattern similar to that of photosynthesis. Specific leaf weight increased slightly on leaves below the defoliated zone, but was significantly reduced on leaves produced subsequent to defoliation. Forest Sci. 28:599-612.

Keywords: >CO2 uptake; biomass; hybrid poplar; leaf development; root growth; specific leaf weight

Document Type: Journal Article

Affiliations: Professor, Department of Forestry, Michigan State University, East Lansing, MI 48824

Publication date: September 1, 1982

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  • Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.
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