Photosynthetic Temperature Acclimation in Eucalyptus Species From Diverse Habitats, and a Comparison With Nerium oleander

Abstract

The response of net photosynthesis per unit leaf area to growth and measurement temperature was measured for Eucalyptus species from diverse natural habitats in Australia and the results compared to Nerium oleander, a species known to exhibit a large degree of temperature acclimation. Eucalyptus species did not show the same degree of temperature acclimation observed for N. oleander in this and previous studies. Photosynthetic acclimation to temperature varied with species of Eucalyptus, apparently in relation to their subgeneric groupings. The estimated parameter, the preferred temperature for photosynthesis, correlated broadly with temperature conditions in the natural habitat.

Estimates of two biochemical parameters, Rubisco (estimated from the initial slope of the A/p_I curve) and RuP₂ regeneration capacity (calculated from the A/p_I curve at high CO₂) were found to parallel changes in assimilation rate. High temperature acclimation in the Eucalyptus species differed from that of N. oleander. Low temperature grown species, except E. miniata, had a higher temperature threshold for reversible inactivation of Rubisco. In E. miniata, Rubisco, but not regeneration capacity, was sensitive to high temperatures in low temperature grown plants. High growth temperatures appeared to affect the thermolability of the photosynthetic components of the two E. pauciflora provenances. Low temperature acclimation was similar for N. oleander and most of the Eucalyptus species and was accompanied by an increase in both biochemical parameters. Regeneration capacity was sensitive to low temperatures in high temperature grown E. miniata.