Agriculture Reference
In-Depth Information
dif erent sizes and shapes of fruit, with plantains being usually very large
compared to the dessert-type bananas or others. The same is true for external
and pulp colour, which normally vary from cream to slight orange.
Growth and development
Pollen sterility is due to triploidy, while female sterility is due to at least
three complementary dominant genes and modifi er genes. These sterility
genes are found in wild populations and have been selected for fruit edibility.
Parthenocarpy is separate from sterility. For the fi rst fortnight after anthesis
the ovules increase in size (50% over initial), and later they shrivel and ovary
growth slows. Parthenocarpic bananas that have seeds ('Pisang Awak' ABB)
show a stimulation of fruit growth, due to the presence of developing seeds.
Pollination can stimulate fruit growth, even without seed development (Israeli
and Lahav, 1986).
There are periclinal and anticlinal divisions from 6 weeks before
infl orescence emergence (anthesis) to 4 weeks after emergence. This division
is followed by cell expansion for 4-12 weeks after emergence. Skin mass
increases rapidly in the fi rst 40 days after fl owering, with the fruit pulp not
beginning to develop until day 40 (Fig. 8.4). Starch accumulation parallels
fi nger length and diameter increases (Lodh
et al.
,
1971). The fruit matures
in the tropics 85-110 days after infl orescence emergence. Fruit development
may take up to 210 days in the cooler subtropics or under overcast conditions
(Table 8.2). Harvest maturity is a commercial stage (three-quarters round),
with the fruit still having some angularity and being only 75% of its potential
maximum size. Export bananas are harvested in the tropics at 14-15 weeks
after fl ower emergence, while plantains are harvested after 11-12 weeks. Fruit
allowed to fully develop to a round shape may show skin splitting. Depending
upon the persistence and viability of the remaining leaves, fully developed fruit
may also show sunburn.
Since fruit number and size decrease from the proximal to the distal
(bottom) hands, fruit thinning is sometimes practised. In most cultivated types,
the bunches bend because of the fruit bunch weight. As the infl orescence
emerges from the pseudostem, it bends towards the sun. Fruits on the inner
whorl of a hand can be 15% smaller than those on the outer whorl. Normally
the last or last two hands that have smaller hands are eliminated if higher fruit
calipers (diameters) are desired. The male infl orescence can be removed soon
after full development of the bunch without damaging the female hands; this
removal reduces the weight and can, in some instances, slightly increase the
caliper of the remaining fruit.
In plantains, there are normally fewer fl owers per bunch, although some
of the new tetraploids have a very heavy load of fruit. Some plantain types do
not have the male part of the infl orescence or it is rudimentary.
