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      Hormonal changes induced by partial rootzone drying of irrigated grapevine

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      Journal of Experimental Botany
      Oxford University Press (OUP)

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          Abstract

          Partial rootzone drying (PRD) is a new irrigation technique which improves the water use efficiency (by up to 50%) of wine grape production without significant crop reduction. The technique was developed on the basis of knowledge of the mechanisms controlling transpiration and requires that approximately half of the root system is always maintained in a dry or drying state while the remainder of the root system is irrigated. The wetted and dried sides of the root system are alternated on a 10-14 d cycle. Abscisic acid (ABA) concentration in the drying roots increases 10-fold, but ABA concentration in leaves of grapevines under PRD only increased by 60% compared with a fully irrigated control. Stomatal conductance of vines under PRD irrigation was significantly reduced when compared with vines receiving water to the entire root system. Grapevines from which water was withheld from the entire root system, on the other hand, show a similar reduction in stomatal conductance, but leaf ABA increased 5-fold compared with the fully irrigated control. PRD results in increased xylem sap ABA concentration and increased xylem sap pH, both of which are likely to result in a reduction in stomatal conductance. In addition, there was a reduction in zeatin and zeatin-riboside concentrations in roots, shoot tips and buds of 60, 50 and 70%, respectively, and this may contribute to the reduction in shoot growth and intensified apical dominance of vines under PRD irrigation. There is a nocturnal net flux of water from wetter roots to the roots in dry soil and this may assist in the distribution of chemical signals necessary to sustain the PRD effect. It was concluded that a major effect of PRD is the production of chemical signals in drying roots that are transported to the leaves where they bring about a reduction in stomatal conductance.

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          Most cited references28

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          Hydraulic lift and water use by plants: implications for water balance, performance and plant-plant interactions

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            The redistribution of soil water by tree root systems

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              Hydraulic lift: water efflux from upper roots improves effectiveness of water uptake by deep roots

              Deuterated water absorbed by deep roots of Artemisia tridentata appeared in the stem water of neighboring Agropyron desertorum tussocks. This supports the hypothesis that water absorbed by deep roots in moist soil moves through the roots, is released in the upper soil profile at night, and is stored there until it is resorbed by roots the following day. This phenomenon is termed hydraulic lift. The potential for parasitism of the water stored in the upper soil layers by neighboring plant roots is also shown. The effectiveness of water absorption by deep roots was substantially improved with hydraulic lift as indicated by reductions of 25 to 50% in transpiration on days following experimental circumvention of hydraulic lift. This phenomenon has important implications for plant water relations, mineral nutrient uptake, competitive interactions among neighboring plants and aridland hydrology.
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                Author and article information

                Journal
                Journal of Experimental Botany
                Oxford University Press (OUP)
                1460-2431
                0022-0957
                September 2000
                September 01 2000
                September 2000
                September 2000
                September 01 2000
                September 2000
                : 51
                : 350
                : 1627-1634
                Article
                10.1093/jexbot/51.350.1627
                11006312
                4ee5f8ce-a815-4e91-9b97-ade5b9d6289d
                © 2000
                History

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