Page 465 - Biosystems Engineering

Exogenous Bior egulators–Fruit Composition & Storability 437

in K level, and a decrease in storage ability. Higher concentrations
(4 to 6 percent), especially when applied at the end of flowering, did
not change (e.g., Gala) or even improve the storage ability of apples
(e.g., Lobo). Increasing the concentration of urea and delaying the
date of its application resulted in improving the mineral composition
of fruit, higher firmness, and higher sugar content.
Urea, applied just after flowering at a low concentration, as an
adjuvant for low concentrations of NAA, caused an increase in firm-
ness and sometimes increased the sugar content as compared with
apples treated only with NAA.
NAA applied just after flowering mainly limited the occurrence
of bitter pit and shriveling during storage. NAA may, however,
diminish firmness and soluble solids content of the sap and may
accelerate ripening. Martin et al. 50,51 reported that NAA applied just
after flowering diminished the incidence of bitter pit and internal
40
breakdown of apples. However, Link reported that NAA increased
the incidence of bitter pit. It is probable that the storage ability of
apples thinned with NAA depends on the rate of crop load reduction
and on the attained fruit size.
CPPU may augment the mineral content of apples, but this phe-
nomenon depended on its concentration and date of application. In
spite of this, CPPU treatment may intensify the occurrence of bitter
pit and internal breakdown, especially when it was applied relatively
late (2 weeks after flowering). CPPU may also increase the firmness
and sugar content of apples. 9,10
BA used for thinning, about 2 weeks after flowering, influenced
apple quality similar to hand thinning but better than NAA. In spite
of the late date of application, BA caused an increase in sugar content
and sometimes improved apple firmness. Apples treated with BA
32
were firmer and contained more sugars than those treated with
NAA. In some conditions, BA may intensify the occurrence of bitter
8
pit and internal breakdown.

15.5 The Influence of Thinning and Treatment with
Calcium Chloride on the Quality of McIntosh
Apples Treated with SADH
SADH applied during the summer on McIntosh apple trees effec-
tively prevents fruit drop during harvest in Poland. However,
65
this treatment sometimes reduces apple size. That disadvantageous
phenomenon usually occurs if SADH is applied too early in the
season. To improve apple size, thinning is the method most commonly
used by fruit growers. In these experiments, trials were conducted to
investigate the influence of fruit thinning on size and other character-
istics of apples treated with SADH.