Unsaturation in the air spaces of leaves and its implications
Cernusak, Lucas A., Chin Wong, Susan, Stuart-Williams, Hilary, Marquez, Diego A., Pontarin, Nicole, and Farquhar, Graham D. (2024) Unsaturation in the air spaces of leaves and its implications. Plant, Cell & Environment. (In Press)
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Abstract
Modern plant physiological theory stipulates that the resistance to water movement from plants to the atmosphere is overwhelmingly dominated by stomata. This conception necessitates a corollary assumption—that the air spaces in leaves must be nearly saturated with water vapour; that is, with a relative humidity that does not decline materially below unity. As this idea became progressively engrained in scientific discourse and textbooks over the last century, observations inconsistent with this corollary assumption were occasionally reported. Yet, evidence of unsaturation gained little traction, with acceptance of the prevailing framework motivated by three considerations: (1) leaf water potentials measured by either thermocouple psychrometry or the Scholander pressure chamber are largely consistent with the framework; (2) being able to assume near saturation of intercellular air spaces was transformational to leaf gas exchange analysis; and (3) there has been no obvious mechanism to explain a variable, liquid-phase resistance in the leaf mesophyll. Here, we review the evidence that refutes the assumption of universal, near saturation of air spaces in leaves. Refining the prevailing paradigm with respect to this assumption provides opportunities for identifying and developing mechanisms for increased plant productivity in the face of increasing evaporative demand imposed by global climate change.
| Item ID: | 83469 |
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| Item Type: | Article (Research - C1) |
| ISSN: | 1365-3040 |
| Keywords: | humidity, intercellular air space, leaf mesophyll, photosynthesis, stomatal conductance, transpiration, water potential |
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| Copyright Information: | This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2024 The Author(s). Plant, Cell & Environment published by John Wiley & Sons Ltd. |
| Date Deposited: | 26 Aug 2024 23:26 |
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