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Xylem sap abscisic acid concentration and stomatal conductance of mycorrhizal Vigna unguiculata in drying soil

Published online by Cambridge University Press:  01 April 1997

ROBERT C. EBEL ,
XIANGRONG DUAN ,
DAVID W. STILL  and
ROBERT M. AUGÉ
ROBERT C. EBEL
Affiliation:
Department of Horticulture, 101 Funchess Hall, Auburn University, Auburn, AL 36849, USA
XIANGRONG DUAN
Affiliation:
Department of Plant and Soil Science, P.O. Box 1071, Knoxville, TN 37901-1071, USA
DAVID W. STILL
Affiliation:
Yuma Valley Agricultural Center, The University of Arizona, 5425 W. 8th Street, Yuma, AZ, 85364, USA
ROBERT M. AUGÉ
Affiliation:
Department of Ornamental Horticulture and Landscape Design, P.O. Box 1071, University of Tennessee, Knoxville, TN 37901-1071, USA
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Abstract

This study was conducted to determine whether xylem abscisic acid (ABA) concentration is altered by mycorrhizal symbiosis of cowpea plants grown in drying soil, and to determine whether stomatal sensitivity to xylem ABA is altered by the symbiosis. We allowed the entire root zone to dry and found that at high soil water contents (θ), mycorrhizal plants had higher stomatal conductance (gs) and lower xylem [ABA] than did non-mycorrhizal plants, but the difference disappeared at low θ, probably because of stomatal closure. The altered gs and xylem [ABA] were apparently not related to plant water status since shoot water potential, xylem sap osmotic potential and shoot water content were similar for mycorrhizal and non-mycorrhizal plants across the range of soil moisture. These differences were also not related to P nutrition or plant size. The relationship of gs to xylem [ABA] was not affected by the symbiosis, indicating that either stomatal sensitivity to xylem ABA was not affected by other xylem constituents, or that more than one xylem constituent was altered by the symbiosis but was offsetting in its effect on gs. We conclude that the symbiosis altered gs non-hydraulically, and that the factor might be xylem ABA.

Keywords

Abscisic acidstomatal conductancecowpearoot signalsdrought
Type
Research Article
Information
The New Phytologist , Volume 135 , Issue 4 , April 1997 , pp. 755 - 761
Copyright
© Trustees of the New Phytologist 1997

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