Impacts of leaf age and heat stress duration on photosynthetic gas exchange and foliar nonstructural carbohydrates in Coffea arabica

Abstract

Given future climate predictions of increased temperature, and frequency and intensity of heat waves in the tropics, suitable habitat to grow ecologically, economically, and socially valuable Coffea arabica is severely threatened. We investigated how leaf age and heat stress duration impact recovery from heat stress in C. arabica. Treated plants were heated in a growth chamber at 49°C for 45 or 90 min. Physiological recovery was monitored in situ using gas exchange, chlorophyll fluorescence (the ratio of variable to maximum fluorescence, F V/F M), and leaf nonstructural carbohydrate (NSC) on mature and expanding leaves before and 2, 15, 25, and 50 days after treatment. Regardless of leaf age, the 90‐min treatment resulted in greater F V/F M reduction 2 days after treatment and slower recovery than the 45‐min treatment. In both treatments, photosynthesis of expanding leaves recovered more slowly than in mature leaves. Stomatal conductance (g s) decreased in expanding leaves but did not change in mature leaves. These responses led to reduced intrinsic water‐use efficiency with increasing heat stress duration in both age classes. Based on a leaf energy balance model, aftereffects of heat stress would be exacerbated by increases in leaf temperature at low g s under full sunlight where C. arabica is often grown, but also under partial sunlight. Starch and total NSC content of the 45‐min group significantly decreased 2 days after treatment and then accumulated 15 and 25 days after treatment coinciding with recovery of photosynthesis and F V/F M. In contrast, sucrose of the 90‐min group accumulated at day 2 suggesting that phloem transport was inhibited. Both treatment group responses contrasted with control plant total NSC and starch, which declined with time associated with subsequent flower and fruit production. No treated plants produced flowers or fruits, suggesting that short duration heat stress can lead to crop failure.

Elevated temperatures impose transcriptional constraints on coffee genotypes and elicit intraspecific differences in thermoregulation

“…Although coffee 43 presents moderate thermotolerance of photosynthetic-related processes, most 44 genotypes produced abnormal reproductive structures at these elevated temperatures 45 (DaMatta et al, 2019). Accordingly, coffee plants subjected to 45°C for 1-to-1.5 hours 46 showed leaf age-related differences in physiological recovery and did not bear flowers 47 or fruits (Marias et al, 2017a). These results demonstrate that, depending on the tissue 48 and stage of plant development, coffee thermotolerance may be substantial regarding 49 physiological parameters.…”

“…This 23 suggests there is potentially useful intraspecific variability of thermotolerance in some 24 genotypes and investigation into the molecular mechanisms underlying this variability 25 is warranted (DaMatta, 2018). 26 Increasing temperature impacts plant physiology from the cellular to the whole 27 plant level and changes photoassimilate allocation to repair and recovery processes 28 (Bita and Gerats, 2013;Bokszczanin et al, 2013;Marias et al, 2017a). However, the 29 stress severity depends on intensity and duration of exposure beyond the plant species 30 and within genotypes (Teskey et al, 2015).…”

“…To the best of our knowledge, a large-scale analysis of 64 3 the intraspecific transcriptional variation in response to elevated temperature has not 65 been reported in Coffee arabica L. and could reveal thermotolerance molecular 66 pathways and important strategies towards breeding programs. 67 Thermotolerance is acquired via protective cellular machinery gained 68 throughout coffee plant maturation (Marias et al, 2017a;2017b). This suggests that 69 young plants are more sensitive and require long-term exposure to stress to acclimatize 70 making this stage in plant development a useful model to examine the impact of warmer 71 temperatures on gene expression during acclimation.…”

Different ways to die in a changing world: Consequences of climate change for tree species performance and survival through an ecophysiological perspective

“…Plant responses to high temperature, in addition to the damage triggered by this stress, vary widely among species and functional groups (Klockmann, Günter, & Fischer, ; Marias, Meinzer, & Still, ; O'Sullivan et al, ; Slot & Winter, ; Teskey et al, ; Wujeska‐Klause, Bossinger, & Tausz, ). Accordingly, the susceptibility of a plant to extremely high temperatures, a situation commonly observed during heat waves, appears to depend on a series of characteristics and adjustments at morpho‐anatomical (crown architecture, leaf size, and shape), physiological (transpiration rate and maximum stomatal conductance), and molecular (production of heat shock proteins, low‐weight compounds, and activation of the antioxidative defense system) levels (Bita & Gerats, ; Galmés, Kapralov, Copolovici, Hermida‐Carrera, & Niinemets, ; Griffin & Prager, ; Obata et al, ; Scafaro et al, ; Slot & Winter, ; Teskey et al, ; Wujeska‐Klause et al, ; Zhang et al, ).…”

Differential submergence tolerance between juvenile and adult Arabidopsis plants involves the ANAC017 transcription factor

“…Beyond acting as exogenous cues that promote stage-specific morphological alterations and acquisition of reproductive competence, environmental stresses also exert variable effects on plant life depending on the developmental stage at which they are experienced. This can be explained by the intrinsic tolerance of organs produced at different developmental stages, as well as changes in the response elicited by the perception of the stimulus, as observed in the case of drought, heat and cold stress (Lim et al , 2014; Marias et al , 2017; Kanojia & Dijkwel, 2018). Understanding stress tolerance mechanisms is extremely relevant to minimize crop yield reduction by adverse environmental conditions.…”