Temperature response of leaf photosynthetic capacity in seedlings from seven temperate tree species

Abstract

Seedlings of seven temperate tree species (Acer pseudoplatanus L., Betula pendula Roth, Fagus sylvatica L., Fraxinus excelsior L., Juglans regia L., Quercus petraea Matt. Liebl. and Quercus robur L.) were grown in a nursery under neutral filters transmitting 45% of incident global irradiance. During the second or third year of growth, leaf photosynthetic capacity (i.e., maximal carboxylation rate, Vcmax, maximal photosynthetic electron transport rate, Jmax, and dark respiration, Rd) was estimated for five leaves from each species at five or six leaf temperatures (10, 18, 25, 32, 36 and 40 degrees C). Values of Vcmax and Jmax were obtained by fitting the equations of the Farquhar model on response curves of net CO2 assimilation (A) to sub-stomatal CO2 mole fraction (ci), at high irradiance. Primary parameters describing the kinetic properties of Rubisco (specificity factor, affinity for CO2 and for O2, and their temperature responses) were taken from published data obtained with spinach and tobacco, and were used for all species. The temperature responses of Vcmax and Jmax, which were fitted to a thermodynamic model, differed. Mean values of Vcmax and Jmax at a reference temperature of 25 degrees C were 77.3 and 139 micromol m(-2) s(-1), respectively. The activation energy was higher for Vcmax than for Jmax (mean values of 73.1 versus 57.9 kJ mol(-1)) resulting in a decrease in Jmax/Vcmax ratio with increasing temperature. The mean optimal temperature was higher for Vcmax than for Jmax (38.9 versus 35.9 degrees C). In addition, differences in these temperature responses were observed among species. Temperature optima ranged between 35.9 and above 45 degrees C for Vcmax and between 31.7 and 43.3 degrees C for Jmax, but because of data scatter and the limited range of temperatures tested (10 to 40 degrees C), there were few statistically significant differences among species. The optimal temperature for Jmax was highest in Q. robur, Q. petraea and J. regia, and lowest in A. pseudoplatanus and F. excelsior. Measurements of chlorophyll a fluorescence revealed that the critical temperature at which basal fluorescence begins to increase was close to 47 degrees C, with no difference among species. These results should improve the parameterization of photosynthesis models, and be of particular interest when adapted to heterogeneous forests comprising mixtures of species with diverse ecological requirements.

Responses of photosynthesis to high temperatures in oak saplings assessed by chlorophyll-a fluorescence: inter-specific diversity and temperature-induced plasticity

“…The thermal treatments therefore mainly induced acclimation (Sharkey, 2005). Nevertheless, a temperature of 35 • C was already at the threshold of damaging levels, as shown by the small decrease of Acer pseudoplatanus, Betula pendula, Fagus sylvatica (Dreyer et al, 2001), in Abies alba (Robakowski et al, 2002) and in Cedrus atlantica and C. libani (Epron, 1997a). These decreases were mainly due to declining levels of maximal fluorescence (F m ) that may reach 65% at 45 • C for Q. pubescens (as compared to a 10% reduction in F 0 ) (Haldimann and Feller, 2004).…”

“…T c can be influenced by a series of environmental parameters like ambient temperature (Dreyer et al, 2001;Havaux, 1993;Robakowski et al, 2002), water availability (Epron, 1997a;Havaux, 1992;Ladjal et al, 2000) and plant growth regulators like ABA (Havaux, 1992;Ivanov et al, 1992). T c varies largely with season, in parallel to ambient temperatures, and increases during summer and decreases during autumn (Froux et al, 2004;Hüve et al, 2006).…”

“…T c is much higher than the optimum temperature for light driven electron flux (T opt ) estimated from the temperature response of J max , the maximal rate of electron flow derived from leaf photosynthesis models. T opt is usually close to 35 • C (Dreyer et al, 2001;Medlyn et al, 2002a). T opt has been shown to acclimate to some extent to long term changes in ambient temperature (Berry and Björkman, 1980;Medlyn et al, 2002b;Yamori et al, 2005).…”

Does ontogeny modulate irradiance-elicited plasticity of leaf traits in saplings of rain-forest tree species? A test with Dicorynia guianensis and Tachigali melinonii (Fabaceae, Caesalpinioideae)

“…To compensate for differences in temperature during measurements, all parameters were scaled to a common reference temperature (T ref ) of 25 • C (298.15 K). Because of the lack of data for tropical tree species, we used the temperature responses computed by Dreyer et al (2001) for seedlings of temperate forest species (Tab. I).…”

Environmental weakening of trophic interactions drives stability in stochastic food webs

“…S2), the shape of the species-environment interaction (here assumed to be Gaussian) could potentially play a more important role (e.g., Laakso et al, 2001). It is realistic to assume that, while not necessarily symmetric, species physiological response to varying temperature is unimodal (Dreyer et al, 2001;Englund et al, 2011;Freitas et al, 2007). However, animals can alter their behaviour (foraging, habitat selection, dormancy, etc.)…”