Page 444 - Biosystems Engineering

Exogenous Bior egulators–Fruit Composition & Storability 421

Retardants (paclobutrazol and daminozide) that have been tested
influenced differently the auxin transportation to tips of shoots. In
this test, daminozide evoked larger changes in the amount of calcium
than paclobutrazol. Some authors report increased Ca uptake by fruit
after applying auxins. 1,47 Also, our results confirmed that auxin can
increase Ca uptake by fruit and leaves treated with retardant in
shoots. However, the amount of Ca in fruit did not change. However,
when retardant was applied to shoots and fruit, auxin acted in a
reverse way (i.e., it slightly decreased calcium uptake by fruits and
leaves). It seems that applying a retardant to shoots only did not
change the auxin’s influence on calcium uptake by leaves; it weak-
ened the transport to the leaves. When a retardant was also applied to
fruit, its influence on calcium uptake caused by auxin was greater
and concerned the leaves, too.
Retardants did not affect unanimously potassium content in ana-
lyzed plant organs. However, paclobutrazol acted more efficiently
than daminozide, although auxin has a distinct influence on potas-
sium uptake, particularly by fruits and seeds. Control fruit not treated
with auxin accumulated the highest amount of potassium. Auxin did
not affect potassium uptake unanimously. It was probably due to the
effectiveness of the retardant. However, in many cases, retardant and
auxin caused an increased K content in seeds.
A joint treatment with retardant and auxin had no great effect on
magnesium content in fruit. A slight increase of Mg in seeds and a
decline of Mg in leaves were observed.
Storage ability assessed on relationship between potassium and
calcium (also potassium plus magnesium and calcium) worsened
after treatment with auxin (Table 15.1). Apples treated with retardant
and not treated reacted similarly to auxin application. In conclusion,
in case of apples with seeds producing endogenous auxins, exoge-
nous auxin depreciates storage ability. It might be caused by too high
an auxin level in fruit. Auxins at high concentrations can be toxic,
limiting the development of fruit and diminishing their size. It was
proven in the presented work. According to Marcelle et al. auxin
47
stimulates Ca transport to fruit but only at low, limited levels. Exog-
enous auxin can intensify calcium transport to partenocarpic fruit, 1
thus these apples store better. According to our results, auxin affected
storage ability similar to giberellin A .
3
Retardants increased the storage ability of apples. A similar effect
was produced in conditions of extreme growth inhibition through
shoot tipping. In fruits with seeds that produce endogenous auxin,
their supply of Ca depends mainly on the sucking power of the
shoots. Retardants diminish the level of auxin-like substances in
shoots and weakens their competition with fruits. As a result, shoots
facilitate a flow of a greater volume of mineral nutrients. Investiga-
tions on the uptake and distribution of calcium using a Ca isotope
confirm this. 7