Partial rootzone drying (PRD) is an irrigation system that permits better control of vegetative growth without reducing fruit yield. However, little is known about how grapevine reproductive development is regulated when irrigated under PRD. Therefore, the aim of this work was to investigate the relationship between abscisic acid (ABA) and polyamines (PAs) in leaves and berries during ripening, and how hormonal balance is affected under different irrigation regimes. The study was carried out using container-grown Superior Seedless grapevines with a split-root system and grown under controlled conditions in a greenhouse. Three irrigation treatments were imposed: control (well watered), and two forms of deficit irrigation – PRD and sustained deficit irrigation (SDI). PRD plants have higher yield and berry size than SDI vines. At the onset of veraison, PRD berries have higher ABA, free PAs and free to bound PA ratio than other treatments. Although the restriction of vegetative growth in PRD might be partly a response to the volume of water applied and therefore similar to a SDI response, our results suggest that specific hormonal factors may explain the effects on reproductive growth and yield.The study demonstrates that changes induced in berry ABA during PRD conditions could be counterbalanced by changes in PA metabolism so that berry size and yield are maintained. (We recommend that you consult the full text of this article)
