When it is too hot for photosynthesis: heat‐induced instability of photosynthesis in relation to respiratory burst, cell permeability changes and H₂O₂ formation

Abstract

Photosynthesis rate (An) becomes unstable above a threshold temperature, and the recovery upon return to low temperature varies because of reasons not fully understood. We investigated responses of An, dark respiration and chlorophyll fluorescence to supraoptimal temperatures of varying duration and kinetics in Phaseolus vulgaris asking whether the instability of photosynthesis under severe heat stress is associated with cellular damage. Cellular damage was assessed by Evans blue penetration (enhanced membrane permeability) and by H2O2 generation [3,3Ј-diaminobenzidine 4HCl (DAB)-staining]. Critical temperature for dark fluorescence (F0) rise (TF) was at 46-48°C, and a burst of respiration was observed near TF. However, An was strongly inhibited already before TF was reached. Membrane permeability increased with temperature according to a switch-type response, with enhanced permeability observed above 48°C. Experiments with varying heat pulse lengths and intensities underscored the threshold-type loss of photosynthetic function, and indicated that the degree of photosynthetic deterioration and cellular damage depended on accumulated heat-dose. Beyond the 'point of no return', propagation of cellular damage and reduction of photosynthesis continued upon transfer to lower temperatures and photosynthetic recovery was slow or absent. We conclude that instability of photosynthesis under severe heat stress is associated with timedependent propagation of cellular lesions.

Transcriptomic resilience to global warming in the seagrassZostera marina, a marine foundation species

“…This finding is in line with studies suggesting that the expression of HSPs and molecular chaperones is correlated with thermotolerance and thermal adaptation (41)(42)(43)48). Most previous studies, however, came from terrestrial organisms, and the duration of the experiment and the period of gene induction were, on average, 10-fold shorter (35,(49)(50)(51)(52)(53). Gene-expression studies in aquatic plants that experience more gradual temperature changes remain largely unexplored (but see refs.…”

Temperature responses of the Rubisco maximum carboxylase activity across domains of life: phylogenetic signals, trade-offs, and importance for carbon gain

“…Given that Rubisco is the most abundant protein in leaves, thermal damage of Rubisco would obviously constitute a very high cost for the plant. Severe damage of leaf photosynthetic machinery typically occurs at relatively high temperatures, above 46-50°C (Seemann et al 1984;Bilger et al 1987;Hüve et al 2011;Sun et al 2013). Such a high temperature threshold could not be achievable without maintenance of the integrity of enzymatic machinery.…”

Temperature Response of Isoprene Emission in Vivo Reflects a Combined Effect of Substrate Limitations and Isoprene Synthase Activity: A Kinetic Analysis

“…Such a temperature response is difficult to explain thermodynamically, except when the biological machinery of the process is being destroyed by the high temperature. This evidently happens at temperatures above 45°C to 50°C, where the response becomes irreversible (Hü ve et al, 2010). However, there is a range of temperatures between 40°C and 45°C for isoprene emission and between 30°C and 45°C for photosynthetic CO 2 uptake, where the inhibition of the process is rapidly reversible when the leaves are returned to lower temperature (Fig.…”