An international research team led by plant biologist Dirk Becker of
Julius-Maximilians-Universität Würzburg (JMU) in Bavaria, Germany, reports
on their novel findings that the plant hormone jasmonic acid is involved in
the quick closure of stomata.

Jasmonic acid is responsible for the aromatic odor of the plant Jasminum
grandiflorum used in cosmetics and perfume industries. When wounded, plants
produce jasmonic acid as a defense signal, as a phytohormone to mount their
defense responses, including the formation of toxic substances. They even
employ volatile derivatives of jasmonic acid to warn their neighbors to
fight the rising threat in time.

Stomata are adjustable pores formed by two guard cells in the epidermis of
plant leaves. They control the uptake of carbon dioxide and the plants'
water balance. The phytohormone abscisic acid (ABA) represents a key signal
for stomatal closure. Plants produce ABA during drought stress to save
water.



In their experiments on guard cell volume control by biotic stress, the team
noticed that mechanical wounding of leaves of the model plant Arabidopsis
thaliana quickly triggers stomatal closure, too. They also noticed that this
effect was not restricted to the wounded leaf, but also occurred in
neighboring leaves. Professor Becker explains that this observation was not
reported before and suggests that the jasmonate signaling pathway might have
been turned-on in the guard cells.



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