Stomatal control and leaf thermal and hydraulic capacitances under rapid environmental fluctuations.

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 adjus...

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Autores principales:	Stanislaus J Schymanski, Dani Or, Maciej Zwieniecki
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2013
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/905d660ce93e4d9299a9f3f85b5e569f
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spelling	oai:doaj.org-article:905d660ce93e4d9299a9f3f85b5e569f2021-11-18T08:00:09ZStomatal control and leaf thermal and hydraulic capacitances under rapid environmental fluctuations.1932-620310.1371/journal.pone.0054231https://doaj.org/article/905d660ce93e4d9299a9f3f85b5e569f2013-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/23359800/?tool=EBIhttps://doaj.org/toc/1932-6203Leaves 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).Stanislaus J SchymanskiDani OrMaciej ZwienieckiPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 8, Iss 1, p e54231 (2013)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Stanislaus J Schymanski Dani Or Maciej Zwieniecki Stomatal control and leaf thermal and hydraulic capacitances under rapid environmental fluctuations.
description	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).
format	article
author	Stanislaus J Schymanski Dani Or Maciej Zwieniecki
author_facet	Stanislaus J Schymanski Dani Or Maciej Zwieniecki
author_sort	Stanislaus J Schymanski
title	Stomatal control and leaf thermal and hydraulic capacitances under rapid environmental fluctuations.
title_short	Stomatal control and leaf thermal and hydraulic capacitances under rapid environmental fluctuations.
title_full	Stomatal control and leaf thermal and hydraulic capacitances under rapid environmental fluctuations.
title_fullStr	Stomatal control and leaf thermal and hydraulic capacitances under rapid environmental fluctuations.
title_full_unstemmed	Stomatal control and leaf thermal and hydraulic capacitances under rapid environmental fluctuations.
title_sort	stomatal control and leaf thermal and hydraulic capacitances under rapid environmental fluctuations.
publisher	Public Library of Science (PLoS)
publishDate	2013
url	https://doaj.org/article/905d660ce93e4d9299a9f3f85b5e569f
work_keys_str_mv	AT stanislausjschymanski stomatalcontrolandleafthermalandhydrauliccapacitancesunderrapidenvironmentalfluctuations AT danior stomatalcontrolandleafthermalandhydrauliccapacitancesunderrapidenvironmentalfluctuations AT maciejzwieniecki stomatalcontrolandleafthermalandhydrauliccapacitancesunderrapidenvironmentalfluctuations
_version_	1718422681799360512

Stomatal control and leaf thermal and hydraulic capacitances under rapid environmental fluctuations.

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