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Stomatal closure in response to xanthoxin and abscisic acid
K Raschke1, R D Firn, M Pierce
1MSU/ERDA Plant Research Laboratory, 48824, East Lansing, Michigan, USA.
Planta
|January 18, 2014
Summary
Xanthoxin (XAN) closes stomata in several plant species when supplied via the transpiration stream, similar to abscisic acid (ABA). However, XAN is less effective on isolated epidermal strips, suggesting conversion to ABA within the plant.
Area of Science:
- Plant Physiology
- Plant Hormones
- Stomatal Biology
Background:
- Stomatal regulation is crucial for plant survival, controlling gas exchange and water loss.
- Abscisic acid (ABA) is a key hormone involved in stomatal closure.
- Xanthoxin (XAN) is a structurally related compound to ABA, and its role in stomatal function requires further investigation.
Purpose of the Study:
- To investigate the effect of xanthoxin (XAN) on stomatal closure in various plant species.
- To compare the activity of XAN with abscisic acid (ABA) in regulating stomatal responses.
- To explore the potential conversion of XAN to ABA within plant tissues.
Main Methods:
- Detached leaves from six plant species (Commelina communis, Hordeum vulgare, Zea mays, Vicia faba, Phaseolus vulgaris, Xanthium strumarium) were used.
- Xanthoxin (XAN) and abscisic acid (ABA) were applied to the transpiration stream and to isolated epidermal strips.
- Stomatal closure was measured in response to treatments.
- The effect of CO2 on stomatal sensitivity to XAN and ABA was assessed.
Main Results:
- Xanthoxin (XAN) induced stomatal closure in detached leaves of all tested species when supplied via the transpiration stream.
- XAN exhibited approximately half the activity of ABA at equivalent concentrations.
- XAN, similar to ABA, increased stomatal sensitivity to CO2 in Xanthium strumarium.
- XAN failed to close stomata in isolated epidermal strips of Commelina communis and Vicia faba, unlike ABA.
Conclusions:
- Xanthoxin (XAN) functions as a stomatal closure agent in intact leaves, with activity comparable to ABA.
- The ineffectiveness of XAN on isolated epidermal strips suggests a metabolic conversion to ABA during transport from the xylem to the epidermis.
- XAN plays a role in ABA-mediated stomatal regulation, potentially acting as a precursor or prohormone.
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