Page 437 - Biosystems Engineering

414 Cha pte r F i f tee n

fruits are due to BRs controlling auxin levels and their transports in
plants. 2,4,43
This work aimed to trace the uptake of mineral nutrients in apple
trees in the condition of shoot growth weakened by retardants. It was
assumed that retardant uptake by shoots would decline, too. Thus,
shoot competition for these elements would be lessened, favoring
fruits. There were also trials to attract nutrient accumulation in fruits
through the application of synthetic auxin. To weaken shoot growth,
two retardants (daminozide and paclobutrazol) were used. Both have
different modes of action. These retardants influence auxin metabo-
lism in the tips of shoots. To assess direct and indirect action of a
retardant in accumulating mineral nutrients in fruits, daminozide
was applied to whole plants or only to the shoots. 11
The research was done in three experiments, each one in a differ-
ent year, on 17- to 20-year-old “Double Red McIntosh” apple trees
grafted onto Antonovka seedlings. To weaken shoot growth, two
retardants—daminozide (Alar, Uniroyal Chemical Co., Middlebury,
Connecticut) and paclobutrazol (Cultar, AkzoNobel, Slough, UK)—
were used. Both preparations were applied 3 weeks after blooming at
0.2 percent concentration in the form of one spray. Daminozide was
given to shoots only in other trees. To protect the fruit, the trees were
covered with aluminium bags that were removed after the prepara-
tion had dried. Chemically pure IAA (Koch-Light, UK) was used as
the auxin. The auxin was given to fruit about 2 weeks after bloom,
3 days after spraying with retardants (first term) or 2 weeks later, that
is, about 4 weeks after bloom (second term). This compound was
given 3 times in three consecutive days: first and second as submer-
sion of fruit in a solution containing 50 mg/L with addition of Tween
20 at 0.1 percent concentration and the third one as an injection of 0.1
percent IAA solution containing 50 mg/L of active ingredient with-
out a wetting agent.
Untreated trees and trees treated with retardant or auxin only
served as controls. Also, trees with 1-year shoots, together with unde-
veloped leaves, tipped off at the time the retardant was applied to
restrain their growth were taken as controls. Another group of control
trees with 1-year shoots were sprayed at the same time with a solution
of gibberellins (Gibrescol, Polfa, Kutno, Poland) containing 500 mg/L
of active ingredient with glycerol as a wetting agent, amounting 5 mL/L
to achieve maximum stimulation of shoot growth. For each treat-
ment, five frame branches were chosen, one per tree (replicate) on
parts of the tree situated in the same cardinal point. Control branches
and branches treated solely with retardants as well as with auxin (one
branch per treatment) have been on the same trees. Just after bloom,
fruitlets were thinned with 1 per spur left.
Analytical material consisted of apples collected at harvest. Fruits
from one branch (about 50 apples) served as the control. Chemical
analysis was made separately on the apples’ flesh and seeds. Because