Page 463 - Biosystems Engineering

Exogenous Bior egulators–Fruit Composition & Storability 435

The influence of urea on the mineral content of the Lobo cultivar
was different than in Gala. In Lobo, the ratio of K and Mg to Ca con-
tent was reduced, which may indicate the improvement of their stor-
age ability. Treating with urea, especially at 2 percent at the beginning
of petal fall, caused an increase in Ca content but also the augmenta-
tion of Mg and P levels jointly with the reduction of K levels. Surpris-
ingly, urea treatment had no influence on the nitrogen content in the
fruit. Urea also had no influence on the firmness and soluble solids of
fruit sap, both at harvest and during storage. Fruit rotting was lower,
as in case of hand thinning. In this experiment, Lobo apples, as well
those treated with urea and hand thinned or unthinned, showed no
symptoms of physiological disorders.
Urea in low concentrations (0.45 to 1.5 percent) applied as an
adjuvant to improve the action of NAA (which was used also in low
concentrations) caused an increase in apple firmness at harvest and
during storage and also increased the sugar level (as compared with
apples treated with NAA alone).
Thinning with NAA alone caused a rise in K and P levels (and
insignificantly of Mg level) in comparison with apples from unthinned
trees, similar to Lobo and Gala cultivars. Apples treated with NAA
alone showed the lowest firmness at harvest and during stored.
NAA-treated apples also showed a high tendency for rotting during
storage. These apples, however, were not prone to bitter pit.
Spraying Lobo trees with CPPU, regardless of its concentration
and date of treatment, had no distinct effect on fruit size or crop load.
Nevertheless, CPPU caused a significant increase in Ca content and
often in K, Mg, and P contents and the reduction of the ratio of K and
Mg to Ca. In spite of this, bitter pit appeared in these apples, espe-
cially in those that were sprayed with CPPU 2 weeks after bloom.
Bitter pit was not observed on the apples from nonthinned trees.
In the case of the Lobo cultivar, no single CPPU treatment visibly
influenced the content of firmness soluble solids. Some treatments
with CPPU limited rotting during storage.
Hand thinning of fruitlets on Lobo trees, in spite of the late date
of administering this treatment, caused an augmentation of Ca con-
tent with no effect on K and Mg levels, and sometimes even lowering
the level of these elements. These apples showed no bitter pit symp-
toms in storage and rotted less than apples from unthinned trees.
The results of four other experiments (3 to 6) indicated that hand
thinning performed after the end of the June drop usually caused a
marked increase in apple size and sometimes diminished rotting and
shriveling of fruits during storage (e.g., Gala cultivar) (Table 15.4).
However, hand thinning promoted the tendency for bitter pit
(e.g., in Gala). Hand thinning sometimes resulted in firmer fruits in
apples from 11-year-old Lobo trees at harvest and during storage.
Hand thinning influenced soluble solids by increasing it in Gala
apples at harvest and in “Gloster” apples at harvest and subsequent