The use of stomatal resistance, photopigments, nitrogen, water potential, and radiation to estimate net photosynthesis in Liriodendron tulipifera L. a physiological index

Author

Curtis John Richardson

Date of Award

12-1972

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Ecology and Evolutionary Biology

Abstract

A physiological index is proposed as an indirect technique of estimating net CO₂ exchange. Multiple linear regression analysis is employed to estimate co-efficients in a linear model relating physiological plant variables, site parameters, and dependent responses for tulip poplar (Liriodendron tulipifera L.) seedlings. Objectives were to (1) ascertain which plant and environmental parameters were the most useful in pre-dicting net photosynthesis under varied conditions, (2) determine the amplitudes of physiological processes (photorespiration, diurnal water flux, seasonal pigment development, stomatal resistance, leaf water potential and net CO₂ exchange) which characterize tulip poplar, and might prove useful in a predictive index, (3) in-vestigate relationships between photopigment ratios and nutrient status, and (4) define empirical relationships between CO₂ uptake and physiological plant parameters and environmental variables. Seasonal ranges of foliar pigments, nutrient con-tent, radiation and precipitation were also measured in the Liriodendron forest to evaluate relationships and techniques that may prove useful in the development of predictive physiological indices for annual forest net photosynthesis. Net photosynthetic rates were predicted from knowl-edge of several plant and environmental parameters: leaf chlorophyll (a+b) content, pigment absorbance ratio 460/663, percent leaf nitrogen, leaf water potential, soil water potential, radiation levels, and stomatal resist-ance. Highest correlation was obtained for sun leaves from a single time period when 99 percent of the variation in net photosynthesis was accounted for by these variables. In all the relationships tested, some indication of plant-water status was necessary to obtain accurate predictions. The removal of leaf and soil water potential reduced the R² to 19 percent. Inclusion of either of these increased the R² to 46 percent. The variation attributable to radiation alone for sun and shade leaves under no water stress (leaf water potential <-20 bars) was 20 percent. By separating sun and shade leaves, radiation accounted for 36 percent of the variation. A single regression was generated which accounted for 61 percent of the variation in net CO₂ exchange when data were utilized from 430 points covering the widest range of fluctuating water levels, shade environments and radiation intensities throughout the growing season. The most important plant and environmental factors for estimating net CO₂ exchange were (l) stomatal resistance, (2) radiation, (3) pigment absorbance ratio, and (4) chlorophyll content. Empirical relations utilizing stomatal resistance, chlorophyll content, absorbance ratio, and radiation were developed which accurately estimate photosynthetic capacity under a variety of conditions.

Recommended Citation

Richardson, Curtis John, "The use of stomatal resistance, photopigments, nitrogen, water potential, and radiation to estimate net photosynthesis in Liriodendron tulipifera L. a physiological index. " PhD diss., University of Tennessee, 1972.
https://trace.tennessee.edu/utk_graddiss/7974