21
RESEARCH
NOTES
TGC
REPORT
No
.
31,
1981
ANNOUNCEMENT
Zamir,
D
.
and
R
.
A
.
Jones
Estimates
of
The
number
of
pollen
grains
applied
to
the
number
of
pollen
grains
applied
a
stigma
in
a
single
pollination
to
a
stigma
in
a
single
pollination
.
greatly
exceeds
the
number
of
ovules
in
the
flower's
ovary
.
The
number
of
fertilized
ovules
can
be
estimated
by
counting
the
seed
produced
per
fruit
.
However,
estimates
of
the
number
of
pollen
grains
which
compete
for
the
precious
few
ovules
are
unavailable
.
The
purpose
of
this
study
was
to
estimate
how
many
pollen
grains
are
applied
to
the
surface
of
the
stigma
in
a
single
pollination,
and,
of
those,
how
many
are
effective
in
fertilization
.
Plants
of
a
male
-
sterile
(ms
10
35
)
tomato
breeding
line
served
as
the
pistillate
parents
for
controlled
crosses
.
The
pollen
sample
was
weighed
before
and
after
pollination
of
360
flowers
.
Pollinations
were
performed
by
dipping
the
stigmas
in
pollen
contained
in
a
gelatin
capsule
.
The
mean
pollen
wt
applied
to
a
stigma
was
6X10
-
6
mg
.
To
determine
the
wt
of
a
single
pollen
grain,
25
mg
of
pollen
was
suspended
in
a
glycerol/water
(25:25
ml)
solution
and
magnetically
stirred
for
1
hr
.
Using
a
haemacytometer,
pollen
grain
numbers
were
determined
in
40
subsamples
of
7
µl
each
.
The
mean
number
of
grains
in
the
subsamples
was
590
.
From
this
dilution
experiment
the
mean
wt
of
a
single
grain
was
calculated
to
be
6X10
-
6
mg
.
Thus
from
the
wt
of
the
pollen
applied
to
a
single
stigma
and
the
mean
individual
pollen
wt,
we
can
estimate
that
about
10,000
pollen
grains
were
applied
to
a
stigma
of
the
male
-
sterile
plant
.
A
different
approach
was
to
estimate
the
number
of
pollen
grains
covering
the
area
of
the
stigmatic
surface
.
Pollen
grain
and
stigma
diameter
were
measured
by
microscopy
.
The
mean
diameter
of
a
single
pollen
grain
was
0
.
021
mm
and
the
mean
stigma
diameter
was
1
.
2
mm
.
As
the
stigmatic
surface
is
of
irregular
shape
and
contoured
with
papillae,
the
total
surface
was
assumed
to
approximate
that
of
half
a
sphere
of
diameter
1
.
2
mm
.
Further
assuming
that
the
packing
of
the
pollen
grains
is
in
the
form
of
a
cubic
lattice,
it
would
take
approximately
5,000
pollen
grains
to
cover
the
stigma
surface
with
a
monolayer
of
grains
.
The
