¥Agronomia vol. 6 n. 2 July

122 Baldini et al.
Analysis of variance was done on the data, and
when the F test proved significant, Duncan’s
test at P ≤ 0.05 was used to separate the mean
values of the treatments. For the data from the
samples taken during the crop cycle the sources
of variation were water regime and sampling
date in the first year, and water regime, hybrid
and sampling date in the second.
RESULTS AND DISCUSSION
Figure 1 shows achene dry matter accumulation
during maturation. As the statistical analysis
demonstrated that the hybrid effect was not significant,
the values reported are the means of
the two hybrids. It should be pointed out that
at the first sampling (two days after the end of
flowering), the embryo begins to form and
therefore all the values relating to that date refer
principally to the tissues of the seed coat,
which forms and develops independently of fertilisation.
The most significant increase in dry
weight took place between 8 and 14 days after
flowering, while between 20 and 28 days dry
matter accumulation in the achene is more or
less completed. Between treatments, water
stress determined the formation of lighter achenes
at maturity compared to the other treatments,
with a higher growth rate in the earliest
stages (8 days after fertilisation), thus confirming
the findings of Hall et al. (1985). Figure 2
shows a strong increase in oil accumulation in
the achene (the values are the mean of the two
hybrids), between the 8th and 14th days after fertilisation,
in correspondence to the significant
Figure 1. 1998. Time course of dry matter accumulation in
achenes of plants submitted to water table (), ET () and
stress () water regimes. The values reported refer to the
mean of the two cv. The vertical bars represent the standard
error of the mean.
Figure 2. 1998. Time course of oil accumulation in achenes
of plants submitted to water table (), ET () and stress
() water regimes. The values reported refer to the mean
of the two cv. The vertical bars represent the standard error
of the mean.
increase in dry matter in the achene (Figure 1).
Among water regimes, the supply from the water
table determined, at maturity, significantly
higher percentages of oil in the achene than in
the other irrigation regimes. However, all treatments
reached the maximum oil content on the
20 th day after the end of flowering, confirming
what Champolivier and Merrien (1996) found
in a trial conducted in a phytotron at the highest
temperatures (27 °C day and 22 °C night),
which are roughly equivalent to those at the trial
site during post-flowering (Table 1).
Figures 3 and 4 give the accumulation of the
major fatty acids in the oil of the high oleic and
standard hybrids for both years.
In the first year of the trial the saturated fatty
acids content (palmitic and stearic) in the high
oleic hybrid diminished rapidly in the days following
the end of flowering, to then stabilise between
the 17 th and 23 rd day at approx. 2.5 and
4%, respectively (Figure 3). The oleic acid content
at the first sampling (74%) was significantly
lower than that found at full-ripening (85%),
while linoleic acid, on the contrary, had a value
of 10% at the first sampling against 5% at maturity.
Both these fatty acids stabilised between
the 17 th and 23 rd day after the end of flowering
(Figure 3).
In the second year the palmitic acid trend
seemed analogous in the two hybrids, with a
slightly higher final amount in the standard hybrid
(5.5%) than in the high oleic one (3%).
This fatty acid reduced, compared to the initial