No evidence of homeostatic regulation of leaf temperature in Eucalyptus parramattensis trees: integration of CO 2 flux and oxygen isotope methodologies
Thermoregulation of leaf temperature (T ) may foster metabolic homeostasis in plants, but the degree to which T is moderated, and under what environmental contexts, is a topic of debate. Isotopic studies inferred the temperature of photosynthetic carbon assimilation to be a constant value of c. 20°C...
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Veröffentlicht in: | The New phytologist 2020-12, Vol.228 (5), p.1511-1523 |
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Sprache: | eng |
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Zusammenfassung: | Thermoregulation of leaf temperature (T
) may foster metabolic homeostasis in plants, but the degree to which T
is moderated, and under what environmental contexts, is a topic of debate. Isotopic studies inferred the temperature of photosynthetic carbon assimilation to be a constant value of c. 20°C; by contrast, leaf biophysical theory suggests a strong dependence of T
on environmental drivers. Can this apparent disparity be reconciled? We continuously measured T
and whole-crown net CO
uptake for Eucalyptus parramattensis trees growing in field conditions in whole-tree chambers under ambient and +3°C warming conditions, and calculated assimilation-weighted leaf temperature (T
) across 265 d, varying in air temperature (T
) from -1 to 45°C. We compared these data to T
derived from wood cellulose δ
O. T
exhibited substantial variation driven by T
, light intensity, and vapor pressure deficit, and T
was strongly linearly correlated with T
with a slope of c. 1.0. T
values calculated from cellulose δ
O vs crown fluxes were remarkably consistent; both varied seasonally and in response to the warming treatment, tracking variation in T
. The leaves studied here were nearly poikilothermic, with no evidence of thermoregulation of T
towards a homeostatic value. Importantly, this work supports the use of cellulose δ
O to infer T
, but does not support the concept of strong homeothermic regulation of T
. |
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ISSN: | 0028-646X 1469-8137 |
DOI: | 10.1111/nph.16733 |