Inhibition of photosynthesis by high temperature in oak (Quercus pubescens L.) leaves grown under natural conditions closely correlates with a reversible heat‐dependent reduction of the activation state of ribulose‐1,5‐bisphosphate carboxylase/oxygenase

Abstract

Inhibition of the net photosynthetic CO 2 assimilation rate ( P n ) by high temperature was examined in oak ( Quercus pubescens L.) leaves grown under natural conditions. Combined measurements of gas exchange and chlorophyll (Chl) a fluorescence were employed to differentiate between inhibition originating from heat effects on components of the thylakoid membranes and that resulting from effects on photosynthetic carbon metabolism. Regardless of whether temperature was increased rapidly or gradually, P n decreased with increasing leaf temperature and was more than 90% reduced at 45 ∞ ∞ ∞ ∞ C as compared to 25 ∞ ∞ ∞ ∞ C. Inhibition of P n by heat stress did not result from reduced stomatal conductance ( g s ), as heat-induced reduction of g s was accompanied by an increase of the intercellular CO 2 concentration ( C i ). Chl a fluorescence measurements revealed that between 25 and 45 ∞ ∞ ∞ ∞ C heat-dependent alterations of thylakoid-associated processes contributed only marginally, if at all, to the inhibition of P n by heat stress, with photosystem II being remarkably well protected against thermal inactivation. The activation state of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) decreased from about 90% at 25 ∞ ∞ ∞ ∞ C to less than 30% at 45 ∞ ∞ ∞ ∞ C. Heat stress did not affect Rubisco per se , since full activity could be restored by incubation with CO 2 and Mg 2 + . Western-blot analysis of leaf extracts disclosed the presence of two Rubisco activase polypeptides, but heat stress did not alter the profile of the activase bands. Inhibition of P n at high leaf temperature could be markedly reduced by artificially increasing C i . A high C i also stimulated photosynthetic electron transport and resulted in reduced non-photochemical fluorescence quenching. Recovery experiments showed that heat-dependent inhibition of P n was largely, if not fully, reversible. The present results demonstrate that in Q. pubescens leaves the thylakoid membranes in general and photosynthetic electron transport in particular were well protected against heat-induced perturbations and that inhibition of P n by high temperature closely correlated with a reversible heat-dependent reduction of the Rubisco activation state.

Adaptability to elevated temperature and nitrogen addition is greater in a high-elevation population than in a low-elevation population of Hippophae rhamnoides

“…The smaller stomatal size in high-elevation population is effective for the inhibition of water loss (Li et al 2006). Previously, similar results have been obtained showing that there are different adaptive responses to warming among different populations (Quercus pubescens and Pinus cembra) in various environments (Haldimann and Feller 2004;Wieser et al 2010). The observed response differences in growth …”

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

“…In Arbutus unedo, such increases occurred above 47 • C (Schreiber and Berry, 1977). Similarly, F 0 was found to remain stable from 25 up to 45 • C in Q. pubescens, revealing a stability of the thylakoid membrane of PSII reaction centres till rather high temperatures (Haldimann and Feller, 2004). The increase of F 0 at high temperatures may be interpreted as a decrease of K P , rate constant for photochemistry, due to fluidification of thylakoid membranes or to less efficient connections between light harvesting antenna and core reaction centres (Ducruet et al, 2007;Yamane et al, 1997).…”

“…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). Such a decrease in F m is thought to result from of a reversible change of the thermal dissipation rate constant K D due to conformational changes in PSII allowing increased thermal energy dissipation (Yamane et al, 1997).…”

Genetic engineering of glycine betaine biosynthesis to enhance abiotic stress tolerance in plants

“…It has been demonstrated that PSII is highly affected by severe heat stress when temperature is above 45°C (Havaux 1996). Moderately high temperatures that normally inhibit CO 2 fixation have no lethal effects on PSII (Haldimann and Feller 2004). Severe heat stress normally affects several photosynthetic processes, while exposure to moderately high temperature impairs the activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), which appears to be the primary limitation to photosynthetic activity (Haldimann and Feller 2005).…”