Agriculture Reference
In-Depth Information
fruit with small, shrivelled seeds. The Hawaiian cultivar 'Grof ' has perhaps
the smallest-sized fruit (approximately 12.5 g), but produces small, shrivelled
seeds, 'chicken tongue', in about 95% of the fruit, greatly increasing the
edible portion to 50-70%. In cultivars with shrivelled seeds, little embryo
development occurs, and the seed growth that does occur stops 30-40 days
from anthesis.
Usually only one of the two locules in the litchi and longan ovary develops
to form a normal fruit. The other aborts and remains at the base of the normal
fruit. Occasionally, both carpels develop equally to form two normal fruit.
The aril tissue in litchi and longan develops from just above the degenerating
obturator and is formed by an outgrowth of the funiculus (Huang
et al.
, 1983).
Aril growth parallels embryo development, though embryo development is not
required for litchi aril growth. If embryo development is arrested during the
liquid endosperm stage and when little embryo growth has occurred, the fi nal
fruit is fi lled with aril and a small aborted seed, called 'chicken tongue' (Huang
and Qiu, 1987). When no endosperm development takes place, no embryo or
aril development occurs and you get a 'hollow' fruit. Both of these conditions
relate to fertilization disorders. Aril development is not uniform and thus
overlaps at the chalazal end of the seed. The aril is therefore free from the seed
in both litchi and longan.
Longan fruit are brownish, globose to ovoid, 1.5-2.0 cm in diameter; the
skin is thin without protuberances and dull green when developing; the aril
is white, translucent and sweet, with an aromatic spiciness. The fruits show
a single sigmoid growth curve, with the major portion of seed development
occurring between 50 and 70 days from anthesis, reaching maturity in 100
days. During early development the seed is the major sink in longan fruit, and
aril growth occurs only after the seed has attained full size and maximum
weight, about 50 days after anthesis (Fig. 9.8b). Growth of aril accounts for
most of the increase of fruit weight during late development and reaches
60-70% of the fruit fresh weight. Growth periods were signifi cantly dif erent
among longan varieties (from 140 to 200 days) and are not correlated to fi nal
fruit size.
Sugar accumulation in the longan aril begins after the main period of
seed development, 70-100 days post-anthesis (Ke, 1990). The fruits can
reach 25% total soluble solids and are ready for harvest when the total soluble
solids reach at least 17-20% and suitable fruit size (above 8-10 g). Sugar
accumulation in the aril begins after the main period of seed development,
70-100 days post-anthesis. The fruits show a dramatic increase in total sugars,
from about 3 to 16-20% during the rapid growth period. The phenomenon is
called 'desweeting' in China and Taiwan. The rate of desweeting varies with
cultivar. Fruits of slow-desweeting types can be retained on the tree longer,
and are better for adjustment of harvest time. The soluble solids of the cultivar
'October' in Taiwan can be maintained above 20% for 50 days.
