ABA xylem concentrations determine maximum daily leaf conductance of field-grown Vitis vinifera L. plants |
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Authors: | M J CORREIA J S PEREIRA M M CHAVES M L RODRIGUES C A PACHECO |
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Institution: | Universidade do Algarve, Campus de Gambelas, 8000 Faro, Portugal;Institute Superior de Agronomia, Tapada da Ajuda, 1399 Lisboa codex, Portugal |
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Abstract: | Differences in maximum leaf conductance in grapevine plants growing in soils with contrasting water availabilities during mid-summer in Portugal could be accounted for by differences in the concentration of ABA in xylem sap. This conclusion is reinforced by the observation that the relationship between leaf conductance and endogenous ABA concentration can be mimicked by the application of exogenous ABA to leaves detached from irrigated plants. During the day, leaf conductance decreased after a morning peak, even when the leaves remained in a constant environment at a moderate temperature and leaf-to-air vapour pressure difference. This decline in leaf conductance was not a consequence of an increase in the xylem ABA concentration or the rate of delivery of this compound by the transpiratory stream. The afternoon depression in leaf conductance was associated with an apparent limitation in stomatal opening potential, which persisted even when detached leaves were fed with water and rehydrated. The reason for this inhibition has still to be identified. |
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Keywords: | Vitis vinifera L soil water status stomatal conductance xylem ABA |
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