Responses of leaf respiration to heatwaves

Abstract

Mitochondrial respiration (R) is central to plant physiology and responds dynamically to daily short‐term temperature changes. In the longer‐term, changes in energy demand and membrane fluidity can decrease leaf R at a common temperature and increase the temperature at which leaf R peaks (Tmax). However, leaf R functionality is more susceptible to short‐term heatwaves. Catalysis increases with rising leaf temperature, driving faster metabolism and leaf R demand, despite declines in photosynthesis restricting assimilate supply and growth. Proteins denature as temperatures increase further, adding to maintenance costs. Excessive heat also inactivates respiratory enzymes, with a concomitant limitation on the capacity of the R system. These competing push‐and‐pull factors are responsible for the diminishing acceleration in leaf R rate as temperature rises. Under extreme heat, membranes become overly fluid, and enzymes such as the cytochrome c oxidase are impaired. Such changes can lead to over‐reduction of the energy system culminating in reactive oxygen species production. This ultimately leads to the total breakdown of leaf R, setting the limit of leaf survival. Understanding the heat stress responses of leaf R is imperative, given the continued rise in frequency and intensity of heatwaves and the importance of R for plant fitness and survival.

Plant mitochondria – past, present and future

“…With global warming comes an increased frequency of heat waves, periods of one or several unusually hot days. Heat waves do not allow plants to acclimate and they can be very damaging to plant fitness and survival, probably because of increased ROS production (Kristiansen et al, 2009;Scafaro et al, 2021). When a cell culture from the tropical coniferous tree Araucaria angustifolia was grown at 25°C and then treated for 6 h at 37°C or 2 h at 42°C to simulate a heat wave, respiration and viability of the cells was unaffected at 37°C, while respiration as well as baseexcision DNA repair enzymes (see Section 5.3) were severely inhibited after treatment at 42°C and the cells subsequently died (Furlanetto et al, 2019).…”

Enhancing crop diversity for food security in the face of climate uncertainty

“…Moderately elevated temperatures will affect all stages and processes of plant development (Lippmann et al., 2019). The expected adverse effects of high temperature on crop growth include decreased seed development and germination (Suriyasak et al., 2020), increased incidence of plant disease and herbivory (Ristaino et al., 2021), altered rates of respiration (Scafaro et al., 2021), photosynthesis (Moore et al., 2021) and photorespiration (Dusenge et al., 2019), and alterations in flowering time (Cao et al., 2021). Moreover, the effects of increased night‐time temperature are expected to be particularly detrimental for crop yield (Sadok and Jagadish, 2020).…”

Scaling plant responses to high temperature from cell to ecosystem

“…Carbon balance can be viewed as a push‐pull dynamic that is driven by mitochondrial respiration and photosynthetic efficiency. Scafaro et al (2021) synthesize current knowledge on how mitochondrial respiration responds to heat, including changes to respiratory metabolism under moderate heat and the inactivation of respiratory enzymes under excessive temperatures. This push‐pull mechanism is further examined by Coast et al (2021), who evaluated the acclimation of both photosynthesis and respiration to higher growth temperatures in wheat and found temperature‐dependent shifts in source‐sink dynamics.…”