Thimmappa S. Anekonda

The relation between plant growth and respiration: A thermodynamic model

A thermodynamic model describing the relation between plant growth and respiration rates is derived from mass-and enthalpy-balance equations. The specific growth rate and the substrate carbon conversion efficiency are described as functions of the metabolic heat rate, the rate of CO2 production, the mean oxidation state of the substrate carbon produced by photosynthesis, and enthalpy changes for conversion of photosynthate to biomass and CO2. The relation of this new model to previous models based only on mass-balance equations is explored. Metabolic heat rate is shown to be a useful additional measure of respiration rates in plant tissues because it leads to a more explicit description of energy relations. Preliminary data on three Zea mays (L.) cultivars are reported. The model suggests new rationales for plant selection, breeding and genetic engineering that could lead to development of plants with more desirable growth rates.

Plant calorimetry. Part 2. Modeling the differences between apples and oranges

Abstract In a previous review we discussed calorimetric methods for the study of plant metabolism. Since that review, a number of papers describing calorimetric measurements examining plant growth, stress responses and effects of temperature have appeared. This recent work is reviewed here. In addition to the experimental work, a mechanistic model linking respiration rates to growth has been published. This model is derived from both mass and enthalpy balance equations. It describes specific growth rate and substrate carbon conversion efficiency as functions of the metabolic heat rate, the rate of CO 2 production, the mean oxidation state of the substrate carbon produced by photosynthesis, and enthalpy changes for conversion of photosynthate to biomass and CO 2 . Application of this model to understanding the basis for variation in growth rates among individual genotypes in plants is reviewed. The effects of environment on the plant respiration-growth relation has been an important focus for plant calorimetry studies. Climatic temperature is one of the most important variables determining growth. Extremes of temperature determine limits of growth, and diurnal variation and mean temperature have a major influence on growth rate. Calorimetric measurements of respiratory rates as a function of temperature can be used to relate the temperature influence on respiratory metabolism to the temperature influence on growth rate. These studies have also discovered the existence of an isokinetic point within the range of normal growth temperatures. Studies of temperature dependence are reviewed and the results analyzed in terms of the recently published mechanistic model.

Site-fitness and growth-rate selection of Eucalyptus for biomass production☆

Abstract Calorespirometric investigation of the metabolism and temperature responses of tissues from Eucalyptus trees can be used to identify plants with superior growth characteristics. Measurements of the metabolic heat rate, rate of CO 2 evolution and O 2 uptake over a range of temperatures are analyzed with a mechanistic model of plant growth to allow early selection of superior trees. This analysis provides information about indexes of genetic characteristics to use in breeding programs and guidelines for matching trees to appropriate climatic conditions. These procedures can enhance the rate of production of biomass by shortening the time to harvest and can increase total economic returns.

Influence of age on dark respiration in eucalypts

Abstract Understanding age-related changes in respiratory parameters is required if measurements of juvenile metabolic properties are to be used for predicting long-term growth rates of trees. This study examines the influence of tree age on respiration in 13 Eucalyptus species, in different genotypes of the same species, and in rooted cuttings (ramets) of a single genotype. All of the respiratory parameters measured — metabolic heat rates, CO 2 production rates, and temperature coefficient of heat rate — showed systematic changes with tree age. Substrate carbon conversion efficiency and specific growth rates calculated from the respiratory data generally decreased with tree age.

Effects of climate on growth traits of river red gum are determined by respiration parameters

Temperature is the major uncontrollable climate variable in plantation forestry. Matching plants to climate is essential for optimizing growth. Matching is usually done with field trials because of the lack of a predictive relation between laboratory measurements of physiological responses and climatic factors affecting growth. This paper evaluates the potential of using respiration parameters for selection of appropriate drainage or seed sources within a drainage for superior growth in a particular climate. The growth traits measured are tree height, stem diameter and stem volume. The respiratory parameters measured are respiratory heat rate, rate of CO2 production, and temperature dependence of respiratory heat rate. Five open-pollinated families from each of nine seed sources of river red gum (Eucalyptus camaldulensis Dehnh.) were studied following selection from a larger set of seed sources planted at three plantations in California. The three plantations differ in climate, particularly in extreme temperatures, diurnal temperature variability and total rainfall. Within each plantation, growth and respiration parameters show high genetic variation (overall coefficient of variation (CV) = 14-58%, family CV = 11-33%), with at least one of these traits showing significant (P < 0.10) difference due to drainage, or source within drainage, or families within source. The relationship of growth to respiration for each trait differs, depending on test plantation, origin drainage, source or family, suggesting a unique pattern for each trait. Correlation of drainage level averages between growth and respiration were strongly negative and significant (P = 0.10-0.01). Rankings for drainages between paired plantations were strong and significant (P = 0.10-0.05) only for respiration, but not for growth traits.