SELECTION FOR BIOMASS PRODUCTION BASED ON RESPIRATION PARAMETERS IN EUCALYPTS - ACCLIMATION OF GROWTH AND RESPIRATION TO CHANGING GROWTH TEMPERATURE

This paper examines the relation between respiratory physiology and gr owth rate and the effects of environment on this relation for the purp ose of developing means for accelerating and improving selection of tr ees for biomass production. The relations among biomass production, re spiratory metabolism, and growth temperature in controlled environment s were determined for three Eucalyptus genotypes (clones). Eucalyptus camaldulensis 4016, E. camaldulensis C11, and Eucalyptus gundal (Eucal yptus gunnii x Eucalyptus dalrympleana hybrid) GD1 were selected for t his study because of known qualitative differences in their field grow th responses to temperature. These clones were grown in controlled env ironments at three temperatures. Measurements were made of growth rate , metabolic heat rate, and dark CO2 production rate for plants grown a t each of the three temperatures. This allowed determination of respir ation rates of plants originally adapted for growth in different clima tes, but acclimated during growth at three different controlled temper atures, and also determination of respiration changes resulting from s hort-term changes in temperature. Growth rates of the three clones dif fered in their patterns of response to changes in growth temperature. For example, C11 grew most rapidly at the highest temperature, while G D1 was slowest at high temperature. Metabolic rates and the temperatur e dependence of metabolic rates of the clones differed and the pattern of differences changed when plants became acclimated to growth at dif ferent temperatures. Changes in metabolic properties of the three clon es with growth and measurement temperatures are consistent with the gr owth rate changes. In general, increased growth rate was accompanied b y increased respiration rate measured either as heat rate or as rate o f CO2 production. Growth rates were inversely related to two measures of metabolic energy use efficiency. Growth rates decreased as values o f heat loss per gram dry weight produced and values of heat loss per m ole of CO2 produced increased. Recognition of these relations between growth rate and respiration parameters at different temperatures in co ntrolled environement may allow prediction of relative growth rate per formance of Eucalyptus clones over a range of growth climates.