Extreme growth phenotypes of trees are caused by differences in energy metabolism

Abstract

Rapid and slow growth phenotypes of same-age-trees can result from differences in genetic growth potential due to differences in the metabolic properties of the phenotypes or by differences in the match between their metabolic characteristics and environmental factors. In this study, paired rapid and slow growing trees from two species were examined to define physiological properties that determine the growth rate differences. Because plant structural biomass production depends on energy production via aerobic respiratory metabolism, respiration rate and energy use efficiencies of the rapid and slow growing trees were compared. Growth rates were calculated for each tree from the measurements of metabolic heat rates and CO 2 production rates of meristems as functions of temperature. The rates of metabolic heat and CO 2 production by respiration were higher, the energy use efficiency was higher, and the rate of storing chemical energy in structural biomass (calculated growth rate) was higher in the large trees than in the small trees, showing that the respiratory metabolic properties define growth rate differences. Ratios of calculated growth rates of large and small trees varied with temperature. Therefore, classification of trees into rapid growth or slow growth phenotypes is dependent upon growth temperature and the match between metabolic characteristics and environment. These findings suggest that respiratory parameters may be used in identifying trees most suitable for rapid growth in a given environment.