percent pollen viability in T
richosanthes dioica, T.
anguina
and
T. cucumerina.
A good percentage of pollen
viability was also noted in
Luffa
spp. (Singh 1957),
Cucumis sativus
(Choudhury & Pathak 1961).
Momordica charantia
(Deshpande
et al
. 1979) and
Lagenaria siceraria
(Singh & Singh 1970).
Nepi and
pacini (1993) observed that in
Cucurbita pepo
the pollen
viability of pollen grains, however, decreases rapidly
and it reached to about 1% in 24 hours.
In Cucurbita
pepo
(Nepi & Pacini 1993) pollen grains lose their
viability very rapidly when dehydration takes place. A
water loss of about 20% causes irreversible damage to
the pollen grains in
Cucurbita pepo
(Kerhoas
et al
.
1986, Nepi & Pacini 1993). The germ pores play a
very significant role in retaining pollen viability. In
T.
dioica
pollen grains have three germ pores. Stanley &
Linskens (1974) correlated decrease in viability with
the stage of development of the male gametophyte and
found binucleate pollen to survive long time than
trinucleate. Pacini
et al.
(1997) found pollen viability
to be decreased with time. Polyploid pollen grains of
Cucumis melo
showed a lower germination percentage
in vitro
and a slower germination rate than haploid
pollen (Susin & Alvarez 1997).