Within-crown Variation in the Development of Photosynthetic Capacity Is Proportional to Growth Temperature in Temperate Deciduous Trees

Abstract

<jats:p>This study set out to test the hypothesis that the development in the capacity for the maximal rate of ribulose-1,5-bisphosphate carboxylase/oxygenase (VC<jats:sub>max</jats:sub>) and the maximum regeneration rate of ribulose-1,5-bisphosphate (J<jats:sub>max</jats:sub>) per unit mass is proportional to the growth temperature under which the leaf develops and to investigate whether the capacity for photosynthetic acclimation to temperature varies genetically within a species by testing genotypes that originated from diverse thermal environments. <jats:italic>Acer rubrum</jats:italic> L. (red maple) genotypes were subjected to short-term and long-term temperature alteration to investigate the photosynthetic response. We minimized the variation of within-crown light gradients by growing trees in open grown field conditions and controlled temperature on a crown section basis. Thus, we singled out the temperature acclimation affects on the photosynthetic temperature optimum. In response to temperature acclimation, the genotype from the northern United States downregulated both VC<jats:sub>max</jats:sub> and J<jats:sub>max</jats:sub> and had a 5 and 3 °C lower temperature optimum than the genotype native to the southern United States. The activation energy increased and was higher for J<jats:sub>max</jats:sub> than for VC<jats:sub>max</jats:sub> in both genotypes. With respect to respiration, both genotypes downregulated about 0.5 μmol·m<jats:sup>-2</jats:sup>·s<jats:sup>-1</jats:sup>. Although respiration was lower, the increased energy of activation in response to growth temperature resulted in a decrease in maximum net photosynthetic rate (A<jats:sub>max</jats:sub>) under saturating light and CO<jats:sub>2</jats:sub>. The results illustrate that the photosynthetic capacity adjusted in response to growth temperature but the temperature optimum was different among genotypes.</jats:p>