to dehisce. Most species used in this survey typi- cally release pollen in the morning or midday
hours. The pollen grains were brushed with a clear camel’s hair brush and cultured at the den-
sity of 50 grains mm
2
on a solid medium according to Brewbaker and Kwack 1963 in
9-cm diameter Petri plates, containing 15 su- crose, 1.5 bacto-agar, 0.01 H
3
BO
3
, 0.03 CaNO
3 2
.4H
2
O, 0.02
MgSO
4
.7H
2
O, 0.01
KNO
3
and 0.01 KH
2
PO
4
. The seeded plates were exposed to two levels of UV-B radiation.
After 1, 2 or 3 h of exposure, the plates were incubated under white light for 7, 6 or 5 h,
respectively. Control group plates were cultured for 8 h only under visible light. Growth of pollen
was stopped by adding some drops of killing and preserving solution comprising water, glycerine,
formaldehyde and glycerol acetic acid 72:20:5:3, v:v to each plate. Plates were stored at 4°C until
pollen germination and tube growth could be scored and measured. Three to five plates were
used for each treatment per experiment, and each experiment was repeated two or three times. At
least 1000 pollen grains per treatment were scored for germination and 50 were measured under a
light microscope for tube length when their elon- gation was greater than pollen diameter.
2
.
4
. Statistical analysis Data were statistically analyzed using a one-
way analysis of variance ANOVA to test the significance of treatment and duration exposure
effect of UV-B except for F. cirrhosa because of insufficient samples. Data of germination was
transformed using the arcsin transformation be- fore the analysis.
3. Results
The effects of UV-B irradiation on pollen ger- mination and tube growth in vitro are shown in
Tables 1 and 2. Enhanced UV-B radiation significantly reduced
P B 0.05 pollen germination of many taxa Table
1. The
species K.
japonica, P.
bretschneideri and F. chinensis, S. oblata var. affinis were insensitive to elevated UV-B P \
0.05. Only in K. japonica an increase in germina- tion percentages under elevated UV-B was found.
S. matsudana f. tortuosa and C. heterostachya showed only increased germination rates under
the highest UV-B dose. Germination percent change against the control was negative
among 16 out of 19 taxa. The highest inhibitory effect on germination was found in F. giraldiana
and F. suspensa. Only S. matsudana f. tortosa, C. heterostachya and K. japonica showed a positive
percent change against the control Table 1.
Similarly, pollen tube length of many species exhibited considerable sensitivity to UV-B Table
2. The adverse effect of UV-B irradiance on tube growth was obvious. The most sensitive species
were F. giraldiana and F. suspensa where pollen tube elongation decreased by 76.2 and 73.7,
respectively, with exposure of 3 h under high UV-B radiation level Table 2. A total of seven
species had no statistically significant reduction of pollen tube growth; they were S. matsudana f.
tortuosa, C. heterostachya, C. bursa-pastoris, F. chinensis, S. pinnatifolia, S. oblata var. affinis, and
P. tomentosa. Pollen tube growth of K. japonica was stimulated significantly under the lower UV-B
flux rate P B 0.05 but significantly inhibited un- der the higher UV-B radiation level P B 0.05
Table 2.
The highest UV-B dose caused a greater inhibi- tion of germination rates and tube growth than
did the lower dose. However, significant differ- ence was observed only in the germination of C.
bursa-pastoris and pollen tube growth of W. sinensis. Germination and pollen tube growth of
60 915 of the species all binuclear pollen grains were inhibited by UV-B. Among four taxa
of trinucleate pollen C. bursa-pastoris, C. het- erostachya, L. maackii, W. florida, germination
of three species and tube length of two dimin- ished, but germination of C. heterostachya a
monocotyledon significantly increased Table 1.
The cumulative effect of UV-B over time is clearly demonstrated. In more than 50 of the
taxa tested, a longer exposure time resulted in a greater reduction of germination rates and tube
growth.
Table 2 Effect of enhanced UV-B radiation on pollen tube growth and percent change of 19 taxa from Lanzhou 36.04°N, 1550 m, China
means 9 S.D.
d
Exposure time Percentage change
Pollen tube growth mm UV-B radiation taxa
c h
Low c High c
High Control
Low 50.4 9 12
1 47.3 9 10.4
9.5 2.6
46.1 9 11.7 S. matsudana f. tortosa Vilm.
Rehd. Salicaceae 12
2 22.0
46.1 9 11.2 51.5 9 12.8
57.1 9 7.1 29.1
39.3 64.2 9 6.9
46.1 9 11.2 3
59.5 9 10.7 67.8 9 2.7
b
1 −
20.2 −
20.1 85.7 9 6.0
a
68.4 9 8.4
b
J. regia L. Juglandaceae 70.0 9 6.1
77.4 9 8.4 −
18.3 −
9.7 2
85.7 9 6.0 67.9 9 14.3
b
73.4 9 10.5
b
− 20.7
− 14.4
3 85.7 9 6.0
a
44.2 9 14.7 −
4.5 −
35.9 52.0 9 8.9
C. bursa-pastoris L. Medic. 68.9 9 5.7
1 Brassicaceae
62.2 9 6.1 40.0 9 7.0
− 9.7
− 42.0
2 68.9 9 5.7
− 22.8
− 37.1
43.3 9 8.2 3
68.6 9 5.7 53.6 9 4.9
47.4 9 7.3
b
1 −
29.1 −
32.9 70.7 9 8.7
a
50.1 9 2.6
b
P. incanus Koehne Saxifragaceae 53.4 9 9.6
b
45.5 9 9.8
b
− 24.5
− 35.6
2 70.7 9 8.7
a
44.9 9 7.7
b
43.4 9 14.8
b
− 36.5
− 38.6
3 70.7 9 8.7
a
169.7 9 8.5 −
6
a
− 10.5
a
179.0 9 6.7 C. speciosa Sweet. Nakai
190.5 9 14.1 1
Rosaceae 2
127.5 9 9.9
c
− 11.8
a
− 33.1
b
190.5 9 14
a
168.1 9 7.1
b
− 26
b
− 31.1
b
130.0 9 12.5
b
140.8 9 10
b
190.5 9 14
a
3 99.8 9 12.5
b
1 35.1
a
− 1.1
a
100.9 9 11
b
136.0 9 11.4
a
K. japonica L. DC. Rosaceae 84.2 9 7.9
b
2 14.4
b
− 16.5
a
100.9 9 9
a
111.0 9 10.1
a
2.3
b
− 40.0
b
60.5 9 15.5
c
103.0 9 10.2
a
100.9 9 11
a
3 123.5 9 7.2
a
79.9 9 11.5
b
− 5.3
a
− 38.8
P. bretschneideri Rehd. Rosaceae 1 130.5 9 12
a
− 10.2
a
− 47.4
68.6 9 10.4
b
117.0 9 12.5
a
130.5 9 12
a
2 67.8 9 13.9
b
3 −
40.1
b
− 48.0
130.5 9 12
a
78.2 9 12.6
b
133.5 9 10
c
− 10.2
b
− 7.3
a
W. sinensis Sims. Sweet. Fa- 1
176.0 9 15.6
a
158.3 9 22
b
baceae −
17.6
a
− 32.6
a
145.4 9 7.7
b
118.9 9 18
a
176.0 9 15.6
a
2 3
92.8 9 11
b
− 16.4
c
− 47.4
b
176.0 9 15.6
a
147.3 9 7.3
b
59.8 9 9.0
b
1 −
40.8
ca
− 48.2
a
115.5 9 8.9
a
68.3 9 9.6
b
F. giraldiana Lingelsh. Oleaceae −
59.1
b
− 68.2
b
36.7 9 10.8
b
47.3 9 8.8
b
115.5 9 8.9
a
2 27.5 9 9.3
b
3 −
73.3
c
− 76.2
b
115.5 9 8.9
a
30.8 9 8.0
b
121.9 9 19
b
1 103.0 9 17.9
b
− 29.8
a
− 40.4
a
173.6 9 17
a
F. suspensa Thunb. Vahl. Oleaceae
− 50.7
b
− 57.0
b
85.5 9 12.7
b
74.6 9 7.2
b
173.6 9 17
a
2 −
55.5
b
− 73.7
c
3 173.6 9 17
a
77.3 9 13.1
b
45.7 9 7.5
c
− 30.9
− 31.6
34.8 9 8.5 1
50.9 9 11.9 F. chinensis Roxb. Oleaceae
35.2 9 29.1 42.4 9 9.6
2 −
6.7 −
16.9 50.9 9 11.9
47.5 9 9.8 45.4 9 16.0
29.8 9 7.2 −
10.9 −
41.5 3
50.9 9 11.9 69.3 9 7.4
76.6 9 12.3 −
17.9 −
9.2 S. oblata Lindl. Oleaceae
1 84.4 9 13.9
− 9.0
− 2.1
82.6 9 11.7 76.8 9 8.2
84.4 9 13.9 2
3 88.2 9 9.3
− 16.4
4.5 84.4 9 13.9
70.6 9 11.5 56.6 9 7.3
b
− 28.8
− 26.3
54.7 9 6.3
b
76.8 9 8.6
a
1 S. oblata var. affinis Henry Lin-
gelsh. Oleaceae 2
54.6 9 13.0 −
12.2 −
28.9 76.8 9 8.6
67.4 9 9.3 41.7 9 10.0
b
55 9 11.8
b
− 45.7
− 28.4
76.8 9 8.6
a
3
Table 2 Continued UV-B radiation taxa
Percentage change Pollen tube growth mm
Exposure time h
c Control
Low High
Low c High c
S. pinnatifolia Hemsl. Oleaceae 1
97.8 9 13.1 85.8 9 8.4
95.5 9 10.9 −
12.3 −
2.4 97.8 9 13.1
87.5 9 9.0 88.6 9 9.9
2 −
10.6 −
9.4 97.8 9 13.1
92.0 9 10.7 74.1 9 7.6
− 5.9
3 −
24.2 1
20.7 9 5.6 23.3 9 7.7
P. tomentosa Thunb. Steud. Scro- 17.1 9 7.7
12.5 −
17.8 phulariaceae
20.7 9 5.6 22.2 9 7.5
16.6 9 6.9 2
7.2 −
20.1 20.7 9 5.6
20.6 9 2.6 20.8 9 9.3
0.6 3
− 3.1
1 316.0 9 15.2
a
300.0 9 11
ab
228.0 9 14.4
b
L. maackii Rupr. Maxim. Capri- −
5.1 −
27.8 foliaceae
2 316.0 9 15.2
a
306.5 9 12
a
243.2 9 12
b
− 3.1
− 23.1
316.0 9 15.2
a
287.4 9 10
b
244.0 9 9.0
c
− 9.1
− 22.8
3 1
190.0 9 11.4
a
169.8 9 7.2
b
W. florida Bge. A.DC. Caprifoli- 168.4 9 6.9
b
− 10.9
− 11.6
a
aceae 190.0 9 11.4
a
174.7 9 5.8
a
149.0 9 12.7
b
2 −
91 −
21.7
b
190.0 9 11.4
a
165.4 9 13
b
140.0 9 11.4
c
− 13.2
3 −
26.2
c
42.5 9 12.6 63.6 9 7.9
52.1 9 8.2 1
49.5 C. heterostachya Bge. Cyperaceae
22.7 42.5 9 12.6
2 45.7 9 8.7
49.8 9 11.3 7.5
17.1 42.5 9 12.6
43.4 9 9.6 45.6 9 15.1
3 2.0
7.3 F. cirrhosa D. Don Liliaceae
134.0 9 11.4
a
2 103.0 9 10.3
b
107.0 9 19.2
b
− 23.1
− 20.1
d
Significantly difference at PB0.05 with LSD test. Values with different letters in the same row the row with symbol within a species show the dose effect and in the same column the column with c symbol show the accumulative effects at PB0.05 levels.
4. Discussion
