Deficit irrigation in grapevine improves water use efficiency by asafwewe


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									Deficit irrigation in grapevine improves water-use efficiency while controlling vigour and
production quality

Chaves M.M.1,2 (, Souza C.R.2,4, Santos T.P.1,2, Rodrigues M.L.1, Lopes C.M.1,
Maroco J.P.2,3, Pereira J.S.1
    Instituto Superior de Agronomia, Tapada da Ajuda, 1349-017 Lisboa, Portugal
    Laboratório de Ecofisiologia Molecular, Instituto de Tecnologia Química e Biológica, Avenida da
    República, Apartado 127, 2780-901 Oeiras, Portugal
    Instituto Superior de Psicologia Aplicada. Rua Jardim do Tabaco, 34. 1149-047 Lisboa, Portugal
     Laboratório de Sementes e Fisiologia Vegetal. EMBRAPA SEMI-ÁRIDO

Drought is one of the most important factors limiting crop yield and quality, worldwide, especially in regions
with climate of the Mediterranean–type. In these regions, viticulturists rely on irrigation water during
drought periods. However, there is considerable controversy concerning the positive and negative effects of
grapevine irrigation regarding growth as well as must and wine quality. On the other hand, with enhanced
pressure on water resources, the increasing demand for vineyard irrigation will only be met if there is an
improvement in the efficiency of water use. This goal can be obtained by several ways, deficit drip-irrigation
practices being the most widely used to save water and simultaneously improve wine quality. We studied
different irrigation regimes in two grapevine varieties (Moscatel and Castelão), during three years. The
treatments were full irrigation or minimum water deficit (FI, 100% of the Etc), deficit irrigated (DI, 50% of
the Etc, half of water supplied to each side of the row), partial root drying (PRD, 50% of ETc periodically
supplied in alternation, to only one side of the root system whereas the other one wa s allowed to dry) and
rainfed, non-irrigated grapevines (NI). The results showed that deficit irrigation treatments (50% Etc)
promoted an increase in water use efficiency (WUE) as compared to full irrigation, either in the short-term,
as expressed by the A/gs ratio or in the long-term shown by the increase in 13C in the plant tissues, especially
the berries. For most of the season, deficit irrigation treatments (PRD and DI) had no negative impact on CO 2
assimilation, despite less water application than in full-irrigation, although they generally showed a larger
relative stomatal limitation (RSL). This is in accordance with the observed higher WUE. Our results also
showed a stability of the photosynthetic machinery in grapevines under low-to-moderate water availabilities,
as demonstrated by the maintenance of the activity of three Calvin Cycle enzymes and of the V cmax values.
However, a decline in Jmax was observed in NI vines, that can be a result either of a decrease in ATP
production or, alternatively of decreased mesophyll conductance to CO2 diffusion. A restriction of growth
was observed in PRD as compared to DI, suggesting that in PRD a chemical regulation on growth was
superimposed on hydraulic signalling, since it showed higher water potential although both received the
same amount of water. Berry temperature of the NI and PRD treatments was always higher than in the denser
canopies (FI and DI) and this was associated with a higher concentration of anthocyanins and total phenols.
No significant differences were observed in yield between the three irrigation treatments even though FI
received twice as much water as PRD or DI. It was also apparent that the response to deficit irrigation varied
with the grapevine variety and with the environmental conditions of the particular year, differences between
treatments being more marked under drier conditions. Differences among varieties may be related to
differences in sensitivity of stomata, shoot growth and/or the interaction between rootstock and cultivar to
soil water availability.

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