UVM Theses and Dissertations
Format:
Print
Author:
Cate, Thomas M.
Dept./Program:
Botany and Agricultural Biochemistry
Year:
2004
Degree:
M.S.
Abstract:
Sugar maple (Acer saccharum Marsh.) is an important tree in the northeastern United States and adjacent Canada. Sugar maple is important not only as a component of forest ecosystems, but also as an indirect economic contributor. Each fall, sugar maple's brilliant foliage helps attract millions of tourism dollars to the greater New England area, and each spring maple sugar production contributes to local economies from Quebec to Wisconsin and as far south as West Virginia. Physiological responses of sugar maple seedlings to their environment can offer clues to the function of seedlings in forest regeneration and hardwood forest ecology. This study used a relatively novel instrument, the chlorophyll content meter (CCM), as part of three studies which explored experimental treatments of adult and seedling-sized sugar maple trees.
The first experiment assessed adult sugar maple trees for response to three soil amendment treatments as a method to determine the usefulness of a CCM as a field instrument. The CCM was able to clearly discern between the control and different soil amendment treatments (Bonferroni-compensated ANOVA, P < 0.001). In the second experiment, a CCM was used to non-destructively assess concentrations of chlorophyll in leaves of adult sugar maple trees and to test the relationship of CCM readings to those generated by pigment extraction and absorbance spectrophotometry, using sugar maple leaves displaying a broad range of color. The purpose of this study was to determine the ability of the CCM to detect chlorophyll under a range of naturally occurring concentrations. The CCM was strongly related with spectrophotometric chlorophyll content (N = 64, r² = 0.72), consistent with other studies using CCMs to determine chlorophyll content in other agronomic and tree species.
In the final study, 33 sugar maple seedlings in pots were assigned to one of three nitrogen-supply treatments: no exogenous nitrogen, 25uM N/week and 250uM N/week (nitrogen as ammonium nitrate, NH₄NO₃). These groups were exposed to treatments of continued watering or water restriction resulting in a 2 x 3 (nitrogen and water restriction) factorial design. Seedlings in treatment groups without exogenous N exhibited a reduced PSII photosynthetic efficiency as determined by increases in baseline fluorescence, F₀ (ANOVA, P < 0.002) and marginally affecting the variable fluorescence Fv (ANOVA, P = 0.056), which suggests sufficient traps for quanta, but insufficient resources for electron transport. Despite significant differences between soil water content (Pw) in the water-restricted and unrestricted treatments, no differences were found between any seedling physiological measures, save fine root N% (ANOVA, P = 0.042).
These studies support the hypothesis that chlorophyll content meters are useful tools for in situ estimation of leaf chlorophyll content in adult sugar maple trees as well as also supporting previous research relating CCM readings and spectrophotometrically-determined chlorophyll content in seedling and adult sugar maple leaves. Sugar maple seedlings with reduced nitrogen availability may prefer biosynthesis of chlorophyll at the expense of downstream electron-transport elements.
The first experiment assessed adult sugar maple trees for response to three soil amendment treatments as a method to determine the usefulness of a CCM as a field instrument. The CCM was able to clearly discern between the control and different soil amendment treatments (Bonferroni-compensated ANOVA, P < 0.001). In the second experiment, a CCM was used to non-destructively assess concentrations of chlorophyll in leaves of adult sugar maple trees and to test the relationship of CCM readings to those generated by pigment extraction and absorbance spectrophotometry, using sugar maple leaves displaying a broad range of color. The purpose of this study was to determine the ability of the CCM to detect chlorophyll under a range of naturally occurring concentrations. The CCM was strongly related with spectrophotometric chlorophyll content (N = 64, r² = 0.72), consistent with other studies using CCMs to determine chlorophyll content in other agronomic and tree species.
In the final study, 33 sugar maple seedlings in pots were assigned to one of three nitrogen-supply treatments: no exogenous nitrogen, 25uM N/week and 250uM N/week (nitrogen as ammonium nitrate, NH₄NO₃). These groups were exposed to treatments of continued watering or water restriction resulting in a 2 x 3 (nitrogen and water restriction) factorial design. Seedlings in treatment groups without exogenous N exhibited a reduced PSII photosynthetic efficiency as determined by increases in baseline fluorescence, F₀ (ANOVA, P < 0.002) and marginally affecting the variable fluorescence Fv (ANOVA, P = 0.056), which suggests sufficient traps for quanta, but insufficient resources for electron transport. Despite significant differences between soil water content (Pw) in the water-restricted and unrestricted treatments, no differences were found between any seedling physiological measures, save fine root N% (ANOVA, P = 0.042).
These studies support the hypothesis that chlorophyll content meters are useful tools for in situ estimation of leaf chlorophyll content in adult sugar maple trees as well as also supporting previous research relating CCM readings and spectrophotometrically-determined chlorophyll content in seedling and adult sugar maple leaves. Sugar maple seedlings with reduced nitrogen availability may prefer biosynthesis of chlorophyll at the expense of downstream electron-transport elements.