Do thick leaves avoid thermal damage in critically low wind speeds?

Leigh, Andrea; Sevanto, Sanna; Ball, Marilyn C.; Close, John; Ellsworth, David S.; Knight, Charles; Nicotra, Adrienne B.; Vogel, Steven

doi:10.1111/j.1469-8137.2012.04058.x

Cited by 144 publications

(120 citation statements)

References 63 publications

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“…Despite the large within-site variation in LMA found at all points along the aridity gradient, there is a significant tendency for LMA to increase with aridity, perhaps because of the resistance to dehydration conferred by stiffer leaves (Niinemets, 2001;Wright and Westoby, 2002;Harrison et al, 2010) and/or the need for leaves to avoid overheating under transient conditions of high radiation load and low transpiration rates combined with low wind speed (Leigh et al, 2012). This increase in LMA is inevitably accompanied by an increasing structural N component.…”

Section: Leaf N and Environmentmentioning

confidence: 90%

Leaf nitrogen from first principles: field evidence for adaptive variation with climate

et al. 2017

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Abstract. Nitrogen content per unit leaf area (N area ) is a key variable in plant functional ecology and biogeochemistry. N area comprises a structural component, which scales with leaf mass per area (LMA), and a metabolic component, which scales with Rubisco capacity. The co-ordination hypothesis, as implemented in LPJ and related global vegetation models, predicts that Rubisco capacity should be directly proportional to irradiance but should decrease with increases in c i : c a and temperature because the amount of Rubisco required to achieve a given assimilation rate declines with increases in both. We tested these predictions using LMA, leaf δ 13 C, and leaf N measurements on complete species assemblages sampled at sites on a north-south transect from tropical to temperate Australia. Partial effects of mean canopy irradiance, mean annual temperature, and c i : c a (from δ 13 C) on N area were all significant and their directions and magnitudes were in line with predictions. Over 80 % of the variance in community-mean (ln) N area was accounted for by these predictors plus LMA. Moreover, N area could be decomposed into two components, one proportional to LMA (slightly steeper in N-fixers), and the other to Rubisco capacity as predicted by the co-ordination hypothesis. Trait gradient analysis revealed c i : c a to be perfectly plastic, while species turnover contributed about half the variation in LMA and N area .Interest has surged in methods to predict continuous leaftrait variation from environmental factors, in order to improve ecosystem models. Coupled carbon-nitrogen models require a method to predict N area that is more realistic than the widespread assumptions that N area is proportional to photosynthetic capacity, and/or that N area (and photosynthetic capacity) are determined by N supply from the soil. Our results indicate that N area has a useful degree of predictability, from a combination of LMA and c i : c a -themselves in part environmentally determined -with Rubisco activity, as predicted from local growing conditions. This finding is consistent with a "plant-centred" approach to modelling, emphasizing the adaptive regulation of traits. Models that account for biodiversity will also need to partition community-level trait variation into components due to phenotypic plasticity Published by Copernicus Publications on behalf of the European Geosciences Union. and/or genotypic differentiation within species vs. progressive species replacement, along environmental gradients. Our analysis suggests that variation in N area is about evenly split between these two modes.

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Section: Leaf N and Environmentmentioning

confidence: 90%

Leaf nitrogen from first principles: field evidence for adaptive variation with climate

et al. 2017

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“…Desert plants are usually fully exposed to sunlight and rely on cooling by mainly radiative and sensible heat flux. In a recent study, Leigh et al [34] investigated the protective role of leaf heat capacity against thermal damage in four desert plant species during short periods with low wind speeds. They simulated leaf temperatures for 0.2 mm thick leaves in comparison to realistic leaves of 0.4–0.6 mm thickness and found that with thinner leaves, two out of the four species could become heat damaged.…”

Section: Discussionmentioning

confidence: 99%

Stomatal Control and Leaf Thermal and Hydraulic Capacitances under Rapid Environmental Fluctuations

2013

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Leaves within a canopy may experience rapid and extreme fluctuations in ambient conditions. A shaded leaf, for example, may become exposed to an order of magnitude increase in solar radiation within a few seconds, due to sunflecks or canopy motions. Considering typical time scales for stomatal adjustments, (2 to 60 minutes), the gap between these two time scales raised the question whether leaves rely on their hydraulic and thermal capacitances for passive protection from hydraulic failure or over-heating until stomata have adjusted. We employed a physically based model to systematically study effects of short-term fluctuations in irradiance on leaf temperatures and transpiration rates. Considering typical amplitudes and time scales of such fluctuations, the importance of leaf heat and water capacities for avoiding damaging leaf temperatures and hydraulic failure were investigated. The results suggest that common leaf heat capacities are not sufficient to protect a non-transpiring leaf from over-heating during sunflecks of several minutes duration whereas transpirative cooling provides effective protection. A comparison of the simulated time scales for heat damage in the absence of evaporative cooling with observed stomatal response times suggested that stomata must be already open before arrival of a sunfleck to avoid over-heating to critical leaf temperatures. This is consistent with measured stomatal conductances in shaded leaves and has implications for water use efficiency of deep canopy leaves and vulnerability to heat damage during drought. Our results also suggest that typical leaf water contents could sustain several minutes of evaporative cooling during a sunfleck without increasing the xylem water supply and thus risking embolism. We thus submit that shaded leaves rely on hydraulic capacitance and evaporative cooling to avoid over-heating and hydraulic failure during exposure to typical sunflecks, whereas thermal capacitance provides limited protection for very short sunflecks (tens of seconds).

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“…New Phytologist Leigh et al, 2012). In particular, larger leaf size in warm-climate genotypes may be an adaptation that optimizes iWUE (Parkhurst & Loucks, 1972).…”

Section: Researchmentioning

confidence: 99%

Genotypic variation in traits linked to climate and aboveground productivity in a widespread C₄ grass: evidence for a functional trait syndrome

et al. 2013

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SummaryExamining intraspecific variation in growth and function in relation to climate may provide insight into physiological evolution and adaptation, and is important for predicting species responses to climate change.Under common garden conditions, we grew nine genotypes of the C 4 species Panicum virgatum originating from different temperature and precipitation environments. We hypothesized that genotype productivity, morphology and physiological traits would be correlated with climate of origin, and a suite of adaptive traits would show high broad-sense heritability (H 2 ). Genotype productivity and flowering time increased and decreased, respectively, with home-climate temperature, and home-climate temperature was correlated with genotypic differences in a syndrome of morphological and physiological traits. Genotype leaf and tiller size, leaf lamina thickness, leaf mass per area (LMA) and C : N ratios increased with homeclimate temperature, whereas leaf nitrogen per unit mass (N m ) and chlorophyll (Chl) decreased with home-climate temperature. Trait variation was largely explained by genotypic differences (H 2 = 0.33-0.85). Our results provide new insight into the role of climate in driving functional trait coordination, local adaptation and genetic divergence within species. These results emphasize the importance of considering intraspecific variation in future climate change scenarios.

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Do thick leaves avoid thermal damage in critically low wind speeds?

Cited by 144 publications

References 63 publications

Leaf nitrogen from first principles: field evidence for adaptive variation with climate

Leaf nitrogen from first principles: field evidence for adaptive variation with climate

Stomatal Control and Leaf Thermal and Hydraulic Capacitances under Rapid Environmental Fluctuations

Genotypic variation in traits linked to climate and aboveground productivity in a widespread C₄ grass: evidence for a functional trait syndrome

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Do thick leaves avoid thermal damage in critically low wind speeds?

Cited by 144 publications

References 63 publications

Leaf nitrogen from first principles: field evidence for adaptive variation with climate

Leaf nitrogen from first principles: field evidence for adaptive variation with climate

Stomatal Control and Leaf Thermal and Hydraulic Capacitances under Rapid Environmental Fluctuations

Genotypic variation in traits linked to climate and aboveground productivity in a widespread C4 grass: evidence for a functional trait syndrome

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Genotypic variation in traits linked to climate and aboveground productivity in a widespread C₄ grass: evidence for a functional trait syndrome