Agriculture Reference
In-Depth Information
12
I
II
III
IV
Huai Zhi
9
6
H-1224
3
0
0 0 0 0
Days after full bloom
40
50
60
70
Fig. 9.6.
Litchi fruit abscission rate, taken as a mean over 2 years, occurs in at least
four stages (I-IV). Normal-seeded 'Huai zhi' (+) harvested 75-80 days after full
bloom and aborted-seeded 'H-1224' (ยท) harvested at 70-75 days after full bloom
(after Yuan and Huang, 1988).
2,4,5-TP (trichlorophenoxypropionic acid), prevented fruit drop to a higher
degree and resulted in more than 75% of the litchi fruit having small seeds.
However, if the infl orescence is fi rst treated with 2,4,5-TP and then sprayed
with a combination of 2,4,5-TP and gibberellic acid, fruits are 50-100%
larger than those treated only once, and 90-100% of the fruits are seedless.
The development of forced fl ower initiation in longan by the use of
potassium chlorate (Fig. 9.7) has extended the production area and also
assured more regular yielding (Yen
et al.
, 2001). However, signifi cant
variations in fl owering application methods have been reported. The variation
is due to variety, developmental status of plants at forcing, soil conditions
and climate (Yen
et al.
, 2005). Potassium chlorate is applied as a soil drench
(200-1000g per tree), either as the salt or in solution is more ef ective than
as a leaf spray (1-2%), injection (1-5%) or trunk girdling (300-600 g).
Treatment with chlorate leads to fl ower induction and the appearance of
fl ower buds in about 40 days, though it can induce leaf chlorosis and drop.
Common bleach decomposes, especially at high temperatures to chlorate and
a level of ~4 g/l has been detected (Matsumoto
et al.
, 2007). Trees treated with
7.6 l of household bleach (~30 g chlorate) were induced to fl ower (Fig. 9.7),
and bleach was more ef ective than 250 g of chlorate. The greater ef ectiveness
of bleach suggests potentially rapid decomposition in the soil to chlorate. The
ef ectiveness of bleach supports an earlier observation that water released
from soybean shoot factories induced longan to fl ower. Bleach is used to
sterilize the seeds before germination and to wash down the equipment.
The rapid induction of fl owers by chlorate means that a longan grower
can take orders for fruit to be delivered 6 months later under good conditions.
