What information is conveyed by an ABA signal from maize roots in drying field soil?

What information is conveyed by an ABA signal from maize roots in drying field soil? ABSTRACT During two seasons, ABA concentrations were monitored in roots, leaves and xylem sap of field‐grown maize. The water status of soil and plant was also measured. Plants were grown on plots with compacted or non‐compacted soil, which were irrigated or remained unwatered. ABA concentration in the xylem sap before dawn and in the roots increases 25‐fold and five‐fold, respectively, as the soil dried, with a close correlation with the soil water status, but with no clear effect of the soil structure. In contrast to the results of several laboratory experiments, no appreciable increase in xylem (ABA) and reduction in stomatal conductance were observed with dehydration of the part of the root system located in soil upper layers. These responses only occurred when the water reserve of the whole soil profile was close to depletion and the transpiration declined. Xylem (ABA) measured during the day was appreciably higher in the compacted treatment than in non‐compacted treatment, unlike that measured before dawn. Since a mechanical message is unlikely to undergo such day‐night alterations, we suggest that this was due to a faster decrease in root water potential and water flux in the compacted treatment, linked to the root spatial arrangement. These results raise the possibility that ABA concentration in the xylem sap could be controlled by two coexisting mechanisms: (1) the rate of ABA synthesis in the roots linked to the soil or root water status, as shown in laboratory experiments; (2) the dilution of ABA in the water flow from roots, which could be an overriding mechanism in field conditions. This second mechanism would allow the plant to sense the water flux through the root system. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Cell & Environment Wiley

What information is conveyed by an ABA signal from maize roots in drying field soil?

Plant Cell & Environment, Volume 15 (2) – Feb 1, 1992

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Publisher
Wiley
Copyright
Copyright © 1992 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0140-7791
eISSN
1365-3040
D.O.I.
10.1111/j.1365-3040.1992.tb01472.x
Publisher site
See Article on Publisher Site

Abstract

ABSTRACT During two seasons, ABA concentrations were monitored in roots, leaves and xylem sap of field‐grown maize. The water status of soil and plant was also measured. Plants were grown on plots with compacted or non‐compacted soil, which were irrigated or remained unwatered. ABA concentration in the xylem sap before dawn and in the roots increases 25‐fold and five‐fold, respectively, as the soil dried, with a close correlation with the soil water status, but with no clear effect of the soil structure. In contrast to the results of several laboratory experiments, no appreciable increase in xylem (ABA) and reduction in stomatal conductance were observed with dehydration of the part of the root system located in soil upper layers. These responses only occurred when the water reserve of the whole soil profile was close to depletion and the transpiration declined. Xylem (ABA) measured during the day was appreciably higher in the compacted treatment than in non‐compacted treatment, unlike that measured before dawn. Since a mechanical message is unlikely to undergo such day‐night alterations, we suggest that this was due to a faster decrease in root water potential and water flux in the compacted treatment, linked to the root spatial arrangement. These results raise the possibility that ABA concentration in the xylem sap could be controlled by two coexisting mechanisms: (1) the rate of ABA synthesis in the roots linked to the soil or root water status, as shown in laboratory experiments; (2) the dilution of ABA in the water flow from roots, which could be an overriding mechanism in field conditions. This second mechanism would allow the plant to sense the water flux through the root system.

Journal

Plant Cell & EnvironmentWiley

Published: Feb 1, 1992

References

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