Assimilate transport in phloem sets conditions for leaf gas exchange

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Carbon uptake and transpiration in plant leaves occurs through stomata that open and close. Stomatal action is usually considered a response to environmental driving factors. Here we show that leaf gas-exchange is more strongly related to whole tree level transport of assimilates than previously thought and that transport of assimilates is a restriction of stomatal opening comparable to hydraulic limitation. Assimilate transport in the phloem requires that osmotic pressure at phloem loading sites in leaves exceeds the drop in hydrostatic pressure that is due to transpiration. Assimilate transport thus competes with transpiration for water. Excess sugar loading, however, may block the assimilate transport because of viscosity build up in phloem sap. Therefore, for given conditions, there is a stomatal opening that maximizes phloem transport if we assume that sugar loading is proportional to photosynthetic rate. Here we show that such opening produces the observed behavior of leaf gas exchange. Our approach connects stomatal regulation directly with sink activity, plant structure and soil water availability as they all influence assimilate transport. It produces similar behavior as the optimal stomatal control approach but does not require determination of marginal cost of water parameter.
Original languageEnglish
JournalPlant, Cell and Environment
Volume36
Issue number3
Pages (from-to)655-669
Number of pages15
ISSN0140-7791
DOIs
Publication statusPublished - 2013
MoE publication typeA1 Journal article-refereed

Fields of Science

  • 1183 Plant biology, microbiology, virology

Cite this

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title = "Assimilate transport in phloem sets conditions for leaf gas exchange",
abstract = "Carbon uptake and transpiration in plant leaves occurs through stomata that open and close. Stomatal action is usually considered a response to environmental driving factors. Here we show that leaf gas-exchange is more strongly related to whole tree level transport of assimilates than previously thought and that transport of assimilates is a restriction of stomatal opening comparable to hydraulic limitation. Assimilate transport in the phloem requires that osmotic pressure at phloem loading sites in leaves exceeds the drop in hydrostatic pressure that is due to transpiration. Assimilate transport thus competes with transpiration for water. Excess sugar loading, however, may block the assimilate transport because of viscosity build up in phloem sap. Therefore, for given conditions, there is a stomatal opening that maximizes phloem transport if we assume that sugar loading is proportional to photosynthetic rate. Here we show that such opening produces the observed behavior of leaf gas exchange. Our approach connects stomatal regulation directly with sink activity, plant structure and soil water availability as they all influence assimilate transport. It produces similar behavior as the optimal stomatal control approach but does not require determination of marginal cost of water parameter.",
keywords = "1183 Plant biology, microbiology, virology, Stomata, photosynthesis, transpiration, optimum, xylem, phloem, long distance transport, viscosity, turgor",
author = "Eero Nikinmaa and Teemu H{\"o}ltt{\"a} and Pertti Hari and Pasi Kolari and Annikki M{\"a}kel{\"a} and Sanna Sevanto and Timo Vesala",
year = "2013",
doi = "10.1111/pce.12004",
language = "English",
volume = "36",
pages = "655--669",
journal = "Plant, Cell and Environment",
issn = "0140-7791",
publisher = "Wiley",
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Assimilate transport in phloem sets conditions for leaf gas exchange. / Nikinmaa, Eero; Hölttä, Teemu; Hari, Pertti; Kolari, Pasi; Mäkelä, Annikki; Sevanto, Sanna; Vesala, Timo.

In: Plant, Cell and Environment, Vol. 36, No. 3, 2013, p. 655-669.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Assimilate transport in phloem sets conditions for leaf gas exchange

AU - Nikinmaa, Eero

AU - Hölttä, Teemu

AU - Hari, Pertti

AU - Kolari, Pasi

AU - Mäkelä, Annikki

AU - Sevanto, Sanna

AU - Vesala, Timo

PY - 2013

Y1 - 2013

N2 - Carbon uptake and transpiration in plant leaves occurs through stomata that open and close. Stomatal action is usually considered a response to environmental driving factors. Here we show that leaf gas-exchange is more strongly related to whole tree level transport of assimilates than previously thought and that transport of assimilates is a restriction of stomatal opening comparable to hydraulic limitation. Assimilate transport in the phloem requires that osmotic pressure at phloem loading sites in leaves exceeds the drop in hydrostatic pressure that is due to transpiration. Assimilate transport thus competes with transpiration for water. Excess sugar loading, however, may block the assimilate transport because of viscosity build up in phloem sap. Therefore, for given conditions, there is a stomatal opening that maximizes phloem transport if we assume that sugar loading is proportional to photosynthetic rate. Here we show that such opening produces the observed behavior of leaf gas exchange. Our approach connects stomatal regulation directly with sink activity, plant structure and soil water availability as they all influence assimilate transport. It produces similar behavior as the optimal stomatal control approach but does not require determination of marginal cost of water parameter.

AB - Carbon uptake and transpiration in plant leaves occurs through stomata that open and close. Stomatal action is usually considered a response to environmental driving factors. Here we show that leaf gas-exchange is more strongly related to whole tree level transport of assimilates than previously thought and that transport of assimilates is a restriction of stomatal opening comparable to hydraulic limitation. Assimilate transport in the phloem requires that osmotic pressure at phloem loading sites in leaves exceeds the drop in hydrostatic pressure that is due to transpiration. Assimilate transport thus competes with transpiration for water. Excess sugar loading, however, may block the assimilate transport because of viscosity build up in phloem sap. Therefore, for given conditions, there is a stomatal opening that maximizes phloem transport if we assume that sugar loading is proportional to photosynthetic rate. Here we show that such opening produces the observed behavior of leaf gas exchange. Our approach connects stomatal regulation directly with sink activity, plant structure and soil water availability as they all influence assimilate transport. It produces similar behavior as the optimal stomatal control approach but does not require determination of marginal cost of water parameter.

KW - 1183 Plant biology, microbiology, virology

KW - Stomata, photosynthesis, transpiration, optimum, xylem, phloem, long distance transport, viscosity, turgor

U2 - 10.1111/pce.12004

DO - 10.1111/pce.12004

M3 - Article

VL - 36

SP - 655

EP - 669

JO - Plant, Cell and Environment

JF - Plant, Cell and Environment

SN - 0140-7791

IS - 3

ER -