Livro das Actas - advid

The variation of stem diameter is sensitive to the addition of soil water (Lubczynski,
2009) and the berry development (de Scheppera et al., 2010). The irrigated vine had a
net gain in diameter while the diameter of the rain fed shrank and the daily shrinkage of
the diameter overcame its daily recovery about 15 days earlier for the rain fed plant relatively
to the irrigated one and this results concur with previous works that draw a relationship
between growth and available water (Ortuno et al., 2010; Sofoa et al., 2012).
The stem diameter of both plants was negatively affected when the berries started growing.
The evolution of the berries size and weight followed closely the results obtained by
other authors (Acevedo-Opazo et al., 2010; Sofoa et al., 2012). The berries grew from
fruit setting to maturation in both equatorial diameter and weight except the ones from
rain fed plants that shriveled in the later stages (fig.3). The incremental growth of the
berries decreased till the onset of veraison and gathered pace afterwards till maturation
(fig.4). The equatorial diameter and the weight of the berries for the rain fed vines
reached, respectively, 12.697 mm and 1.650 g, while for the irrigated plants were, respectively,
19.862 mm and 3.281 g.
The growing berries competed for the water (Intrigliolo and Castel, 2007), but the rate
reduction was smaller for the irrigated plant. Once the irrigation was suspended (12 August),
the variation rate of the stem diameter in irrigated plants showed an almost immediate
change (14 August).
The sap flow daily variations showed the regular pattern already observed in other research
works with a decreasing flow during the night and increasing during the day in
response to higher evaporative demand from the atmosphere. The mean flow is 2,0 and
2,5 L dm-2 h-1 , respectively, for rain fed and irrigated grapevines. The sap flow values
were very similar on both vines before the irrigation period, they became divergent during
irrigation, to converge again when irrigations was suspended. The rain fed vine
started increasing the flow rate at lower level than the other vine in early June and once
the irrigation started the irrigated plant kept an higher rate at all times till irrigation was
suspended when the rates on both vines converged (fig. 5).
The sap flow rate depends on water availability (Cifre et al., 2005) but also on the atmospheric
conditions (Pataki and Oren, 2003) and on the plant control such as stomatal
409
Livro Actas