Intracanopy adjustment of leaf-level thermal tolerance is associated with microclimatic variation across the canopy of a desert tree (Acacia papyrocarpa)

Abstract

Why this research is novel and significant: We provide novel, mechanistic insight into how localised variation in microclimate drives intracanopy variation in thermal tolerance, providing a new consideration for whole plant function and optimisation. AUTHOR CONTRIBUTIONS: AL and EMC generated hypotheses and designed the thermal tolerance work; EMC collected and analysed the data; CAK provided advice and contributed fundamental intellectual input; EMC led the writing, with AL revising the final text.

Plant heat stress: Concepts directing future research

“…Different facilities, including leaf chambers (Schrader, Wise, Wacholtz, Ort, & Sharkey, 2004), plant chambers and glasshouses (Dusenge, Madhavji, & Way, 2020; Jagadish et al, 2010), field‐based tents (Bergkamp, Impa, Asebedo, Fritz, & Jagadish, 2018), radiant heaters (Ruiz‐Vera et al, 2013; Ruiz‐Vera, Siebers, Drag, Ort, & Bernacchi, 2015) and naturally hot summer months (Sathishraj et al, 2016) are used to quantify genetic diversity in heat tolerance and understand physiological and molecular responses to heat stress. Although these approaches provide critical opportunities to advance heat stress research, they each address limited aspects of the heat stress response in plants (Aronson & McNulty, 2009) by altering the immediate micro‐climate surrounding crops (Julia & Dingkuhn, 2013), leaves at different positions within tree canopies (Curtis, Knight, & Leigh, 2019) and even tissues within a single rice panicle (Fu et al, 2016)or at different developmental stages (Shi, Ishimaru, Gannaban, Oane, & Jagadish, 2015; Shi, Lawas, Raju, & Jagadish, 2015). Aligning measured plant responses to changes in the micro‐climate and the temperature experienced by plants will provide more reliable insights into how heat stress affects plants and helps us develop strategies that can encompass heat tolerance and recovery.…”

“…Although these approaches provide critical opportunities to advance heat stress research, they each address limited aspects of the heat stress response in plants (Aronson & McNulty, 2009) by altering the immediate micro-climate surrounding crops (Julia & Dingkuhn, 2013), leaves at different positions within tree canopies (Curtis, Knight, & Leigh, 2019) and even tissues within a single rice panicle (Fu et al, 2016) or at different developmental stages (Shi, Ishimaru, Gannaban, Oane, & Jagadish, 2015;Shi, Lawas, Raju, & Jagadish, 2015). Aligning measured plant responses to changes in the micro-climate and the temperature experienced by plants will provide more reliable insights into how heat stress affects plants and helps us develop strategies that can encompass heat tolerance and recovery.…”

Leaf heat tolerance of 147 tropical forest species varies with elevation and leaf functional traits, but not with phylogeny

“…Variation in heat tolerance among co‐occurring species may represent functional or ecological differences in micro‐climate adaptation among species. For example, Sapper (1935) already showed that sun species have higher heat tolerance than shade species, and even within species, heat tolerance tends to be moderately higher in sun‐exposed leaves than in shade leaves (Curtis, Knight, & Leigh, 2019; Slot, Krause, Krause, Hernández, & Winter, 2019). Within site variation may also reflect different evolutionary histories of plants.…”

Photosynthetic heat tolerances and extreme leaf temperatures

“…A recent common garden experiment used cooling and warming treatments to show that plant communities from warmer climates generally exhibit higher mean heat tolerances than communities from colder climates, but that climate did not explain variation in heat tolerances among individual species (Zhu et al., 2018). In a separate study, the variation in the heat tolerances of 42 species grown in a botanical garden were attributed to physiological adaptions to microhabitat, and not climate (Curtis, Knight, & Leigh, 2019). Similarly, Knight and Ackerly (2002) speculated that differences between heat tolerances of congeneric species measured in situ, and those measured in a common environment were attributable to changes in leaf temperature.…”