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Stomatal conductance in relation to xylem sap abscisic acid concentrations in two tropical trees, Acacia confusa and Litsea glutinosa

Liang, J., Zhang, J., Wong, M.H.
Plant, cell and environment 1996 v.19 no.1 pp. 93-100
Acacia confusa, leaf conductance, stomatal conductance, abscisic acid, sap, xylem, soil water content, water stress, soil compaction
Two tropical trees, Acacia confusa and Litsea glutinosa, were grown under controlled conditions with their roots subjected to soil drying and soil compaction treatments. In both species, a decline in stomatal conductance resulting from soil drying took place much earlier than the decline of leaf water potential. Soil compaction treatment also resulted in a substantial decrease in stomatal conductance but had little effect on leaf water potential. A rapid and substantial increase in xylem abscisic acid (ABA) concentration ([ABA]), rather than bulk leaf ABA, was closely related to soil drying and soil compaction. A significant relationship between stomatal conductance (gs) and xylem [ABA] was observed in both species. Artificially feeding ABA solutions to excised leaves of both species showed that the relationship between gs and [ABA] was very similar to that obtained from the whole plant, i.e. the relationship between gs and xylem [ABA]. These results suggest that xylem ABA may act as a stress signal in the control of stomatal conductance.