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Advisor(s)
Abstract(s)
The objective of this study was to evaluate the effect of
deficit irrigation on intrinsic water use efficiency (A/gs)
and carbon isotope composition (δ 13C) of two grapevine
cultivars (Moscatel and Castelão), growing in
a commercial vineyard in SW Portugal. The study
was done in two consecutive years (2001 and 2002).
The treatments were full irrigation (FI), corresponding
to 100% of crop evapotranspiration (ETc), rain-fed (no
irrigation, NI), and two types of deficit irrigation (50%
ETc): (i) by supplying the water either to one side of the
root system or to the other, which is partial rootzone
drying (PRD), or (ii) dividing the same amount of water
by the two sides of the root system, the normal deficit
irrigation (DI). The water supplied to the PRD treatment
alternated sides approximately every 15 d. The values
of predawn leaf water potential (ψpd) and the cumulative
integral of ψpd (Sψ) during the season were lower
in 2001 than in the 2002 growing season. Whereas
differences in Wpd and SW between PRD and DI were
not significantly different in 2001, in 2002 (a dryer year)
both cultivars showed lower values of SW in the PRD
treatment as compared with the DI treatment. This
suggests that partial rootzone drying may have a positive
effect on water use under dryer conditions, either
as a result of better stomatal control and/or reduced
vigour. The effects of the water treatments on δ13C
were more pronounced in whole grape berries and
pulp than in leaves. The δ13C of pulp showed the best
correlation with intrinsic water use efficiency (A/gs) as
well as with Sψ. In spite of the better water status
observed in PRD compared with DI in the two cultivars
in 2002, no statistical differences between the two
treatments were observed in A/gs and δ13C. On the
other hand, they showed a higher δ13C compared with
FI. In conclusion, it is apparent that the response to
deficit irrigation varies with the environmental conditions
of the particular year, the driest conditions
exacerbating the differences among treatments. The
highest values of d13C found in the pulp of NI vines in
Castela˜o compared with Moscatel suggest different
sensitivities to water deficits in the two cultivars, as
was empirically observed.
Description
Keywords
Carbon isotope composition Deficit irrigation Grapevines Partial rootzone drying Water use efficiency
Citation
Journal of Experimental Botany, 56 (418), 2163-2172