Agroecology 2 min

Stomata and starch: the dark side of plant water loss

PRESS RELEASE - Leaves lose water through tiny pores called stomata. In most plants, stomata open during the day and close at night. A new study conducted by L’Institut Agro and INRAE, published in The Plant Cell, shows that stomata reopen during the night depending on the level of starch stored in the leaves the previous day. This discovery offers new prospects for selecting more water-efficient plants.

Published on 07 June 2023

illustration Stomata and starch: the dark side of plant water loss
© Gilles Pantin

Leaves have tiny pores called stomata, which are surrounded by a pair of guard cells. In the vast majority of plants, stomata open during the day, facilitating the capture of atmospheric CO2 —indispensable for photosynthesis — but leaving the door open for water vapour to escape through transpiration. At night, stomata close, enabling the plant to save water when photosynthesis is no longer empowered with sunlight. However, depending on the species, or even the variety, residual nighttime transpiration may result in inefficient water loss.

More than a century ago, observations under the microscope revealed that stomata progressively reopen throughout the night (see references). This reopening of stomata depends on the circadian clock — the plant’s internal timer that is entrained by the day/night cycles. In addition, starch in the leaves acts as a transitory metabolic clock: starch is synthesised during the day through photosynthesis, and used at night to generate sugars, making it the main source of energy at night. Could starch metabolism play a role in the nighttime reopening of stomata?

To answer this question, the authors used the model plant Arabidopsis thaliana to study the dynamics of water loss. They worked with Phenopsis high-throughput phenotyping platform, and developed a new series of computational tools, called PhenoLeaks, to analyse the dynamics of plant transpiration By screening a series of plants whose starch metabolism was differentially affected, the team discovered that severe mutations in starch metabolism prevented stomata from reopening at night and, unexpectedly, altered the rhythm of stomatal movements throughout the day. This means that the plant uses starch not only as a source of energy but also as a means of adjusting its circadian clock.

The authors also discovered that stomata did not react to the starch available in their own guard cells, but rather to the starch in the leaf as a whole. In other words, the bulk starch content keeps stomata on time, most likely through the sugars generated in the internal tissues of the leaves, which travel to the guard cells to "set the local time". A great way for the plant to keep all its


Westgeest A.J., Dauzat M., Simonneau T., Pantin F. (2023). Leaf starch metabolism sets the phase of stomatal rhythm. The Plant Cell, koad158,

Loftfield JVG (1921) The behavior of stomata. Carnegie Institution of Washington, Publication No. 314. Washington, USA

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Scientific contact

Florent Pantin Lecturer at L’ Institut Agro on secondment at INRAEUMR LEPSE and UMR IRHS



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