Page 436 - Biosystems Engineering

Exogenous Bior egulators–Fruit Composition & Storability 413

changing their size. It is probably for this reason that in the experiments
by Ben, Jonagold apples treated with BA 3 weeks after flowering
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9
were affected by flesh browning. Also, in experiments by Basak, BA
that was applied after flowering to thin fruitlets sometimes reduced
the keeping quality of apples.
The results of using BRs depend on many environmental and
agrotechnical factors, and often also on the concentration, time, and
method of application, as well as tree age, species, and even cultivar.
For that reason, the literature often contains contradictory informa-
tion on the effects of the same BRs on the mineral composition of
fruits.
To synthesize all this information is extremely difficult because,
in many experiments, the mineral composition of fruits was regarded
as an additional observation. Moreover, most of the studies concerned
the effect of BRs on the mineral composition of leaves. Many experi-
ments concerning the effect of BRs on the uptake of mineral nutrients
were carried out on young, not-yet-fruiting plants, or their parts,
growing under controlled conditions. The results of such experiments
do not fully reflect the mineral nutritional status of plants already
bearing fruit and growing in the field.
Taking into consideration the present state of knowledge, it can
be stated that BRs can improve the mineral composition and storabil-
ity of fruits, but it is difficult to predict the results that using these
substances can produce because they depend on both environmental
conditions and tree physiology. Thus, it does not seem likely that BRs
can be used for controlling Ca nutrition of fruits.

15.2 Fruit Quality
Quality of fruit such as an apple is closely related with the apple’s
mineral composition; among them calcium has a special meaning. Ca
content and its relationship with other elements decide about apple
resistance to physiological disorders in storage. 17,70 The uptake of
mineral nutrients, calcium in particular, was the subject of many
investigations. The process is complicated and dependent on the
physiological state of trees. BRs and other preparations influence
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uptake and distribution of minerals, among them calcium. 7,11,26,47,72
Apple trees take the highest amount of Ca in spring at the time of
intensive shoot growth. In condition of weak shoot growth, the fruit
59
supply with calcium improves, but at strong shoot growth it wors-
ens. There is much evidence that retardants that are natural growth
70
inhibitors favor the accumulation of Ca in fruit. 21,51,59
Calcium moves to fruits and shoots mainly acropetally; however
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transport is related to the basipetal movement of auxins. Auxins
are mainly delivered by seeds, young leaves, and other intensively
growing parts of plants. It is presumed that quantitative changes in