Agriculture Reference
In-Depth Information
80
60
40
100 leaves per panicle
50 leaves per panicle
2 leaves per panicle
20
0
0
10
20 30
Days from full bloom
40
50
60
70
Fig. 9.4.
Effect of leaf number on the litchi panicle branch to number of fruit set per
panicle for cultivar 'H-1224' (after Yuan and Huang, 1988).
developed two-carpel pistil and a two-lobed stigma (Fig. 9.3). The fi ve to
eight stamens do not dehisce normally and have little viable pollen. Type III
fl owers function as a male, though they are morphologically a hermaphrodite
with a rudimentary pistil lacking style and stigma. The six to eight stamens
produce numerous viable pollen grains. Approximately two-thirds of the
fl owers on a panicle are composed of Type III and only about 20% of the
fl owers are potentially fruit-producing (Type II). Observations indicate that
the ratio of functional females (Type II) to functionally staminate fl owers
(Types I and III) varies with cultivar (Table 9.2), with 10-30% being female
(Limangkura, 1966). Similar sex types occur in longan (Lian and Chen,
1965), of small, greenish-yellow to brownish, self-incompatible fl owers
having fi ve sepals and fi ve petals (Fig. 9.5). Insects are the major pollinators
(Alexander
et al.
, 1982).
Litchi fl oral anthesis occurs in cycles of sex types (Mustard, 1954), with a
period of about 10 days during which only functional male fl owers are open.
This is followed by a transitional period of 2-3 days when both staminate
and female (Type II) fl owers open, then 2 days of only female fl owers. This is
followed by 2-3 days of transitional types, and fi nally male fl owers for a period
of 7-10 days. The number of days to complete each of the cycles appears
to dif er somewhat among infl orescences and between cultivars and with
environmental conditions. Infl orescences produced around the same time
generally produce the same sex types. It has been observed that the initial
fl owers are all functionally male in one season, and in the following season
initial fl owers at one site may be all functionally female and at another site
all functionally male. Thus, the infl orescence may begin fl oral anthesis at any
sexual phase of the cycle, going through the above sequence. The expression
