Selection for biomass production based on respiration parameters in eucalypts: acclimation of growth and respiration to changing growth temperature

Abstract

This paper examines the relation between respiratory physiology and growth rate and the effects of environment on this relation for the purpose of developing means for accelerating and improving selection of trees for biomass production. The relations among biomass production, respiratory metabolism, and growth temperature in controlled environments were determined for three Eucalyptus genotypes (clones). Eucalyptuscamaldulensis 4016, E. camaldulensis C11, and Eucalyptusgundal (Eucalyptusgunnii × Eucalyptusdalrympleana hybrid) GD1 were selected for this study because of known qualitative differences in their field growth responses to temperature. These clones were grown in controlled environments at three temperatures. Measurements were made of growth rate, metabolic heat rate, and dark CO2 production rate for plants grown at each of the three temperatures. This allowed determination of respiration rates of plants originally adapted for growth in different climates, but acclimated during growth at three different controlled temperatures, and also determination of respiration changes resulting from short-term changes in temperature. Growth rates of the three clones differed in their patterns of response to changes in growth temperature. For example, C11 grew most rapidly at the highest temperature, while GD1 was slowest at high temperature. Metabolic rates and the temperature dependence of metabolic rates of the clones differed and the pattern of differences changed when plants became acclimated to growth at different temperatures. Changes in metabolic properties of the three clones with growth and measurement temperatures are consistent with the growth rate changes. In general, increased growth rate was accompanied by increased respiration rate measured either as heat rate or as rate of CO2 production. Growth rates were inversely related to two measures of metabolic energy use efficiency. Growth rates decreased as values of heat loss per gram dry weight produced and values of heat loss per mole of CO2 produced increased. Recognition of these relations between growth rate and respiration parameters at different temperatures in controlled environement may allow prediction of relative growth rate performance of Eucalyptus clones over a range of growth climates.