Exine Structure of Pantoporate Campanula (Campanulaceae) Species

16 Pages·1992·10.9 MB·

by  Joan W Nowicke

i
STRUCTURE
EXINE OF
Joan W, Nowickey^ Stanwyn
G. Shetler,^
and Nancy
PANTOPORATE CAMPANULA Morin^
(CAMPANULACEAE)
SPECIES^
Abstract
The only species in Campanulaceae known to have pollen with pantoporate apertures are five species of Campanula:
C
C, americana, C. californica^ C. exigua, C. and sharsmithiae. All other species examined of this large
griffinii,
300 The
genus (ca. species) have 3-4(-7) pores, spaced equidistant on the equator of the grain. pantoporate species,
especially the widely distributed annual or biennial herb C. americana, are further distinguished by elongate or well-
may
developed columellae. The larger columellae of this species be correlated with their lower density. Except for
the similarities in pollen, C. americana does not appear closely related to the three slender annuals, C. exigua, C.
and C. sharsmithiae^ each of which has a restricted distribution in California. Campanula americana also
griffinii,
C
not closely related to the pantoporate perennial, californica^ or to the fourth California annual, C. angustiflora,
is
which has 4-6-zonoporate pollen with a tectum and exine structure almost identical to C. sharsmithiae. The pantoporate
grains of C. californica, with pores that are not always uniform in size or distribution, and the zonoporate grains of
may
C. angustijloray with unevenly distributed pores and elongate columellae, represent transition stages between
Campanulaceae
the two pollen types. In this study and previous ones, all species of with well-developed or elongate
Whether more make
columellae have been shown to have a high number (more than five) of apertures. apertures
the pollen wall more vulnerable to collapse and whether selective pressures have resulted in a more rigid wall by
means of elongate columellae are debatable. The highly distinctive pollen-collecting hairs found in the Campanuloideae
are and
illustrated discussed.
In a systematic study of four closely related Although not specifically studied here, the pol-
annual species of Campanula, endemic to Cal- lination biology of Campanula, the species of which
all
ifornia, Morin (1980) established the existence of show pronounced protandry and adaptations to in-
pantoporate characterized by a unique and
(pores distributed over the entire sur- sects, is still largely
unexplained mechanism. While the flower
griffi is still
and
Morin, and C. sharsmithiae Morin, and 4-6-zono- in bud, anthers dehisce deposit the pollen on
the pollen-collecting hairs of the upper As
style.
ifl
Morin (unpublished) found the pantoporate aper- anthesis proceeds, both pollen and the unicellular
hairs gradually disappear, the former owing
rermial C. calif to pol-
(Kell. Heller), Prior to her studies only one other linator activity, the latter to retraction/invagina-
expanded The
annual or tion into their bases. fact that in
some
Campanula cases the retracted hair observed "to trap"
biennial americana native to east- is
L,,
has prompted
ern and central North America, was known to have a pollen grain speculation that the
an autogamy
a pantoporate aperture type (Avetisian, 1967; invagination is adaptation for (for
Dunbar, review, see Shetler, 1979). This does not seem
1973a, 1975a, 1981, 1984; Shetler, to
b, b,
&
1982; americana be the case (Shetler, 1982; Lloyd Yates, 1982),
for life history of C. see Shetler,
&
1958, and The unusual however; the possible functions of the collecting
Baskin Baskin, 1984).
hairs are presented in the discussion section.
lim
in Campanulaceae prompted investigation of
this
exme
Methods
and
Materials
the
California pantoporate species.
For examination of pollen, anthers were
re-
sub]
mov herbarium
fundamental
tolyzed (Erdtman, 1966) for preparations:
rod all light
microscopy (LM), scanning electron microscopy
like or
threadlike structures
TEM
We preparation and John Skvaria for the preparation of
pollen
' thank Carol Annable for her assistance in
Campanula
sharsmithiae.
wr
t • • Washim_-gton, i-.
Museum Smithsonian Institution. D.C. 20560,
Natural History.
' Department Botany National of
of
L.S.A.
631660299, U.S.A.
Box 299, Louis, Mifisouri
' Missouri Garden, P.O. St.
Botanical
Card. 65-80.
Ann. Missouri Bot. 79: 1992.
66 Annals of the
Garden
Missouri Botanical
and tectum
copy (SEM), transmission electron microscopy porate apertures a that consists of
and
(TEM), and plasma spinules irregularly oriented threadlike or
-ashing. rod-
SEM, 1-41,
For pollen was coated with carbon, then like structures (Figs. 54, 55, 57, 58). For
Dunbar
and examined and photographed porate Campanulaceae, (1984:
gold-palladium,
1) classi-
250
with a Cambridge Stereoscan Electron Micro- fied surface sculpture types into the following cat-
scope or a Hitachi 570 SEM, egories: ridges; ridges, with top end bent upwards;
TEM,
For pollen was incoi:porated into agar, fingerlike structures; protrusions; irregular ridges; ^
fixed with osmium tetroxide, stained with uranyl and reticulum in low relief. With the exception of
Campanula
acetate, and embedded in Spurrs resin or L. R. the last category, applicable only to
we
White. After sectioning, the pollen was stained in americana in our study, believe that these
lead citrate and examined in a JEOL 100, 1200EX, closely related categories are minor variations in
200 Although
or a Philips transmission electron microscope. the orientation of the rods or threads.
LM,
For pollen was mounted in glycerin jeDy the term rod, with implication of a straight or
its
may
and sealed with paraffin. Measurements (see Table erect linear structure, be more fitting for some
are based on 20 grains LM. tecta than others, Figure 41 versus Figures
1) in e.g.,
For examination of collecting hairs, styles were 55 or 58, we will use rod in the remainder of the
(
dissected from herbarium flowers and attached to text to describe the ropelike strands making up the
specimen stubs, coated with gold-palladium, and surface of the tectum, often intertwined in spaghet-
examined and photographed in a Cambridge 250 tilike fashion. These rods can vary in their size,
S410
or an scanning electron microscope. The degree of distinction (e.g.. Figs, 15, 31 vs. 9, 41),
examined 35 and
collections are listed in Table 1. extent of projection (e.g., Fig. vs. 38, 41),
In plasma-ashing an electrical changes orientation mostly horizontal as in Fig- 35 or
field di- (e.g.,
atomic oxygen into excited oxygen ions to form a with rods more erect /vertical as in Figs. 17, 23,
highly reactive plasma that causes low temperature and
46).
combustion of organic molecules. The most com- In SEM, the relationship between the rods and
—
mon
appear
use of plasma-ashing is for removal of organic spinules seems clear the free tips of rods
Campanula
matter from
inorganic structures, e.g., tissue from to coalesce to form spinules. In every
sponge For SEM, some
spicules. this application, end-point de- species examined in the base of at least
tectors can determine precisely when the organic spinules continuous with three or more rods. This
is
layers have been removed. In completely plasma-ashed
organic condition the
illustrated best in
is
samples such as exines, however, the only control samples. Figures 56 and 59, but ahnost as well in
(available to us) is duration of ashing. Based on an Figures 8, 29, 38, 41, and 58. In the past (Dunbar,
earlier study of pollen from 33 species representing 1973a; Morin, have been con-
1980), the spinules
&
we now
owic
but
sidered as basally rooted or divided,
ir
oduces the most profound a think that the spinules are the result of free tips
taring of rods coalescing and not of rods formed by the
in skeletonlike exines. For greater detail, see No- basal subdivision of spinules (see discussion below).
wicke
et al. (1986). In thin section, species examined have strat-
all
LM EM
and
All slides micrographs are deposited ified exines with an endexine, foot layer, columel-
at the Palynological Laboratory, National Museum lae, and tectum, but these components are van-
of Natural History, Smithsonian
Institution, ously developed.
poUen oi
Based on
the above the
characteristics
a
Campanula with
porate
a recognizable type:
is
tectum and oriented
consisting of spinules variously
Results
n
two
rods. But the pores defines
distribution of the
n
In the course of the entire Campanulaceae study, distinctive subtypes with very unequal frequencies,
the pollen of 5 8 collections representing 41 species Five species are pantoporate 7, 13, 21,
(Figs. 1,
mined SEM, many
and
24), with as few as apertures and as
six
examined
som^-
»?enty- as 8. All remaining campanulas have three,
1
LM
examined a
times more (seven in
in four, or rarely five or six
TEM.
examined
few grains of C. rotundifolia) pores placed equ>-
For most
the part only the species that are cited distant on the equator of the grain (some grains of
the and/or
in text Ulustrated are given Table
in 1. C. anguslijlora excepted).
Campanula TEM
All 18 species of cited Table Our
in differ-
1 investigation revealed subtle
have
oblate-spheroidal
or spheroidal pollen with ences panto-
in the structure of the exine: the
in
Si
Table examined, voucher and numbers.
S}jccic6 data, pollen data, figure
1.
Number
Pore of CD
Species Collection Location Figure(s) Grain pores
size^ size
CO
&
Campanula alpina Jacq. Bujorean Nyarady 7/1/23 Romania 28-30 P(28) 30 X E(30) 32 4-5.2 3
s.n, (32) (35)
C
amerirana L. Danaske 2128 Wisconsin (36) 38 (40) 5.2-6.5 12-15 3
Shimek 8/15/27 3-6 10-13
38 5.2-6.5
s.n. low, (35) (40)
CD
&
Soper Dale 4081 Canada 1.2 38 5.2-6.5 10-13
(35) (39)
1472 62-69
Hartley Wisconsin
60.
WardsM. 4/7/1878
Maryland 61
C. angustijlora Eastwood Constance aL 3045 16-20 P(29)31 X E(31)34(36) 4-6.5
et California (32) (4-)6
C
barbata L. Hermann 19483 France 33-35 P(29) 32 X E(30) 31 5.2-6.5 3
(34) (34)
C
biiumgartcnii Becker Hall 3125 Germany 57-59 P(27)29(31) X E(30)31(43) 3-4
5.2
J.
MrMurphy
22 24-27
C. californiia (Kill.) H**ller California 40 2.6-4 7-11
(39) (45)
2116
C. fiivarirnta Mic hx. Allard Virginia P(30) 32 X E(32) 35 5.2-6.5 3
(35) (36)
Duncan 11925
South Carolina P(29)31 (34) X E(32)34(36) 5.2 3
C
&
exigrta Rattan Sharsmith Sharsmith 3358 40 12-14
California 7,8, (36) (42) 5.2
10-12
Morin 297 (MO)
California 9 35 4-5.2 12-15
(34) (38)
glome
r. rata L. CoUins Fernahl 1904 Canada P(29)30(34) X E(31)33(38)
<?- s.n, 4.5-6.5
(2)3(4)
m
Morin 20 (MO)
C. g^iffinii Griffin 4 1 California 13, 14 (30)31(34) 5.2-6.5 6-9 X O
Hon 21813
ell California 15 33 4-5.2 7-12
(30) (35)
O
C CD
hagutin Rrrhinger 3678
Roisft. Greece 31,32 P(21) 23 X E(22) 25 3.9-5.2
(25) (26) 3(4)
C/)
C
CD
la^inrarpn Cham. 7/15/61
llultvn $M. Alask P(30) 32 X E(31) 33 5.2-6.5 3-4
(35)
(35)
C CD
DC &
Cay
FTiarrorAira ex A. fTiUzck Dutoit 21-Vn-30 France P(27) 29 (30) X E(29) 31 4-5.2
(33) 3
(2)
(4)
C
0)
mrrfium Thomas 10926
L. Montana 54-56
P(34) 37 X E(36) 39
(39) 3
(40)
C
CD
rhomboidaiis 37599
L. Maillrfrr 36-38
Switzerland P(26) 29 X E(28) 29 4-5.2 O
(31)
(34) 3(4)
C
rolundifolia L. Charpin 7/15/69
et at. $.n. Italy 39 P(32) 37 X E(34) 36 5.2-6.5 3-4
(40)
(41)
3858
Colorado 40.41 P(30) 33 X 36
(38) E(34) (41) 5.2-6.5 4(5)
C, iharsmiihiae Morin Morin 301 (MO) 21-23 I
California (35) 38 (40) 4-5.2 12-18
C
2977
sibirira L. r^ato
Romania
P(29)32(34) X E(31)33(36)
5.6-7.1
(2)3(4)
5U1
Codonopsi'f bulleyana Rock
51-53
China
P(41) 44 X E(41) 46 17-36 6-8
(48)
(49)
0)
Forrrst ex Diels
C
rnrtvolvulacea Kurs Rock 6603
42-44
China P(38)42(48) X E(43)46(51) 7.8-13
6
Githopsis pair h Vatke CoHilance 5/19/51
ilia 45-47
s.n. Califo rnia P(36) 40 X E(39) 43 5.8-7.8
(45) (47) 6
DC
tf'ahlcnbergia Unarioidrs Schtmr: 10R77
48-50
Argentina P(25) 28 X
E(29) 31 4.5-5.2
(30) (32) 3(4)
inieat
a
iks: numbe
lar diniension;
C7>
'
68 Annals of the
Garden
Missouri Botanical
The remaining pantoporate
prominent pollen of the species,
porate type the or
project through the tectum to form the core of
life
21
sharsmithiae
igures 10, 11, 19, 20, 12), C. (Figs.
5,
^"Z-
LM
13-1 was examined and SEM.
27, whereas in the zonoporate type the columeDae finii (Figs. 5), in
The were examined TEM,
are reduced Figs. 30, 32, and 37) and the first three species also in
(e.g.,
C
4*
annual, angustifi
columella
Campanula
The nnial califc
has a well-developed foot layer (Figs. 32, 34, (Figs. 24-27) has the elongate columellae asso- *'
ally
with the DantoDorate type, but the distri
37).
i.
A
complete description of each pollen type bution and size of the pores are not unifo
is
LM
numerous
given below; for pollen size, the range of the mean there are grains that, in optical
have pores on the "equator';
(Table given. section, four to six
1)
is
»
may
each hemisphere and bottom focus) have
(top
—
emi,
PANTOPORATE POLLEN TYPE FIGURES 21-27
1-15,
hemisphe
^
Pollen spheroidal, 31-40 /im diam., with 6-18 a pore; very frequently one of the pores is distinctly
even LM,
4-6.5 The obvious in
pores, the pores /im diam., the tectum con- smaller. elongate spinules,
from
sisting of rods and spinules, or microreticulate and would distinguish the pollen of C. californica
remaining
spinulate; exine structure consisting of lamellate
all
endexine prominently thickened at the pores; the tions suggest that the pollen of C. califc
but
foot layer mostly thin or sometimes eaual betwe
in thick- int
zonoporate.
ness to the nonapertural endexine; the columellae closer to the pantoporate than to the
elongate, prominent, at least some of which project Campanula exigua 7- 12-15 pan-
(Figs. 1 2) is
through the tectum to form the core of most sometimes
spi-
tectum
nules; the incomplete or nearly complete rods
4
jmericana, and endexine are simila
sities of the foot layer
iffif
them
C. C. and making characterize
life ta, C. (Fig. 11), difficult to
g^iffi it
sharsmithiae. form well-defined
individually, but together they a
Campanula
americana 1-6) 12-15- becomes much near the pores,
(Figs. unit that thicker
is
pantoporate with a microreticulate tectum in which The columellae, although not as large as in C.
m
mebu-
rods americana, predominant layer
are the
Campanula
species of examined in this study or poral (nonapertural) areas, and most appear to
form the
illustrated in others (Dunbar, 1973a, b, 1975a, project through the irregular tectum to
1984; Morin, 1980) has a microreticulate tectum core of the spinules. Their elongation is under-
or such massive columellae. The rods/rauri and scored in tangential section (Fig. 11) by the pro-
spinules are more evident in some grains than in portion of the area they occupy. In botn
total
others. In thin section (Figs. 3-5), the exine of C. rods dis
americana some
and
consists of a lamellate endexine present tinct from each other and are short,
throughout
the grain but greatly thickened near appear
vertical.
the pores and with a thin foot layer. Comparison
grifiniiy
Griffi
C
of radial sections of americana
(Fig. 3) with oDorate with a
1
C
those of other pantoporate
species, exigua
e,g., tectum
(Fig. 11), C. sharsmithiae (Fig. 22), and C. cal was 8-11 more poorly de-
15), -pantoporate with
fined rod
tectal
{f<
12'
alpina and
e.g., C. (Fig. 30) C. hagiela Campanula 21-23)
(Fig. 32), sharsmithiae is
(Figs.
emphasizes the unusual development
of the colu-
with
mellae in C. americana. Larger columellae may as rods,
sist of irregularly defined elements as well
be a compensation
or species
for, correlation with, fewer In exme
thin section 22) the of this
(Fig.
The
columellae
density of columellae that
in the tan- consists of a thick, mostly lamellate endexine
gential section of C. americana much foot
(Fig. 4) is is slightly less electron dense than the thin
lower than that exigua when which
in C. (Fig. 10): a layer and weU-developed some of
columellae,
Ihe
grid
proiect through the tectum form spinules.
to
columellae
e structures
nvunber of columellae ami
for C,
similar.
C
while that for C. exigua was 30. c^
In contrast Campanula americana^
to
-
Number
Volume Nowicke 69
79, et
1 al.
Campanula
1992 Exine Structure of
— —
SEM SEM
Figures 1-6. SEM and TEM of Campanula americana pollen. 1. of two pantoporate grains. 2.
—
TEM Note massive columellae, some of which project through
of tectum. 3. of radial section including part of pore.
TEM
the tectum, and endexine nearer the pore,— 4. of tangential section. Perforated tectum
thickened, lamellate
TEM
6.-5.
(outer SEM, Figures 2 and of mostly radial section through whole
ring) agrees with that portrayed in
gram. otherwise indicated.
tectum ;im unless
1
form spinules; exine structure consists of a lamel-
ifornica^ C. exigua, C,
griffi
much
becomes
endexine that thicker near the
knowledge late
a well-developed foot layer that thicker
pores;
pollen that 3-4(-7)-zonoporate. is
is
than the nonapertural endexine; reduced or short
and a complete or almost complete
— columellae;
zonoporate
pollen type
smaD
with to large spinules that are not
tectimi,
Figures
16-20. 28-41. 58
54. 55. 57, continuous with columellae.
C
The pollen of seven zonoporate species,
diameter al-
Pollen mostly oblate-spheroidal, Polar
28-30),
pina C. angustiflora
(25-)31- Jacq. (Figs. (Figs.
(23-)29-37Mm x diameter
Equatorial
C
C barbata 33-35), baum-
16-20), L. (Figs. C.
39 3-4
the
fim, pores (rarely 7, rotundifolia),
hamela
Becker 57,
^artenii (Figs. 58), C. Boiss.
(= J.
pores circular or elongated polarly lo- ,
slightly
rhomh,oida, li, s
C. L. (Figs. 36-38),
4.0-6.5 Mm, the (Figs. 31, 32),
longateX dimension
the longest
difoli
With
quently with a free some of which coalesce to
tip,
Annals the
70 of
Garden
Missouri Botanical
—
--o-
Figures 7-15. SEM 8.
grain.
igua. of pantoporate
7.
TEM Note
tectum tectum
section.
10. ooff tangential
—
TEM
ol
and
tectal perforations the large area occupied by columellae cut at right angle to their long axes. 11-
—
radial section. Note prominent columellae, some of which project through tectum, 12. TEM of section of whole
—
C
SEM fewer
grain. Note buildup of endexine near apertures. 13-15. 13. of wwhnooliee ggrraaimn.. Note llaarrggeeir atxnnd^ *--^
griffinii. I'NOie
—
SEM " ^S'E"*M' a«nnnotthheer
apertures than in the remaining pantoporate species. 14. of tectum.— 1^ 5. of*• tectum ^from
=
coUection (see Table 1). Scale bars 1 /xm unless otherwise indicated.
Number
Volume Nowicke
79,
1 et 71
al.
1992 Exine Structure of Campanula
C
SEM
SEM TEM Campanula poUen. 16-20. anguslijl. 16. of zonoporate
grainn.
Figures 16-23. and of
TEM
-17. SEM tectum.- 18. o! section of whole Th
of grain.
Note and
irregularity of pore distribution size.
clo« bemg
indicates that the section is to paraHel with the
that the four apertures are similar in size
visible >
they are well above or below the equator.- TEM
on the right side 19.
equator apertures
of the grain. If there are
TEM
-20.
through tectum.
Note some columellac project tin: of tangential
that
including part of pore.
2\-2^
and \0 C.nharsmitkiae.-2]. SEM
Figures 4
section. Compare columeUae and area occupied with of
size
endexme
and lamellate md.-ates
TEM The thickened proximity an
-22. to
section.
pantoporate of radial
grains.
-
Figure
angustijlora. 17. Scale Lars unlw,
aperture.-23. SEM Compare with tectum of C. 1 ^n.
of tectum.
otherwise
indicated.
-
72 Annals of the
Garden
Missouri Botanical
SEM TEM
Figures 24-32.
and Campanula SEM
24-27. grain-
of pantoporate
pollen. C. californica.—24:. of
—
SEM
Note long TEM
spines. 25. of tectum diameter
with part of pore. 26. of tangential section. Compare the
—
jmmcuae TEM
with those in Figure 10 of C. exigua and in Figure 37 of C. rotundifolia. 27 of slighdy
.
C
dial sections of two grains. Note elongate columellae and the direct connection with spinules. 28-30.
SEM
alpina. 28. —of zonoporate grain in equatorial view.— 29. SEM of tectum with pore. Note direct relationship
TEM
of spines with rods. 30. of oblique sections of two grains. 31, 32. C. hagiela.— SI. SEM of tectum. Note
small irregular-sized spinules and lack of distinction of rods.— 32. TEM of grain including
radial section of collapsed
two Note =
walls. well-developed foot layer, small columellae, and almost continuous unless
tectum. Scale bars 1 iiia
otherwise
indicated.
of C. angustiflora, discussed separately below, the Campanula 36-38) has
rhomboidalis
(Figs,
exines of the above species are grain
similar: irregularly pollen with three pores on the equator of the
oriented rods that are distinct, e.g.. Figure 41 or and a tectum of the
(Fig. 38) that representative
, is
TEM
barely Figure and
visible, e.g., 31, poorly devel- genus. In most prominent unit
(Fig. 37) the
oped
or short columellae with the foot lay er/endex- columellae
the
is foot layer /endexine, while the
ine the predominant component
(Figs. 30, 32, 34, are very
short
37, 40). Of TEM,
the zooporate examined
species in
73
Nowicke
Number et
Volume 79, al.
1
Campanula
Exine Structure of
1992
I
I
SEM
33-35. barbata. 33. of zonoporate gi
C.
TEM Campanula poUen.
SEM
Figures and of
SEM
C of polar view of 3 porate
rhomboidalis.- 36.
36-38.
TEM ^^ SF.M tectum.
.^^ of
39
- tectum. 41. C. rotumlifc
1
6"™^
TEH secHon. »' •"" „^
grain.- obBqua radial '°^^
37. o( slightly ^„ion. TTo met
^romto=,.t
„f
component
is
ri
sJk
74 Annals of the
Garden
Missouri Botanical
I
Campanula harhata (Fig. 34) has the most well- lower grain In Figure 47 to Codonopsis convol-
U
vulaceae
defined, albeit short, columellae. (Fig. 44).
Campanula The Wahlenhergia
Although pollen of linarioides
the pollen of angustiflora (Figs.
16-20) zonoporate, the higher number of 48-50) 3-zonoporate with a typically campan-
(Figs. is is
pores —(4-6) and their somewhat irregular distri- ulaceous tectum and exine structure.
bution necessarily equidistant from each oth- As part of an earlier study (Nowicke et al., 1986)
^not
—
two
er and not on the equator distinguishes this of substructure of distinct pollen types (a corn-
all
many pound [= and
pollen from zonoporate types. Moreover, the layer of striae lirae] a derived
tri-
3
tectum and exine structure link this armual to the angular array) that occurred together in a number
C
Some
pantoporate ones. grains of angustiflora of families, exines of Berberidaceae, Cistaceae, Eu-
(Fig, 17) have a tectum that almost indistin- phorbiaceae, and Geraniaceae were partially de-
is
C
guishable from some grains of sharsmithiae graded by plasma-ashing (see Materials and Meth-
—
To
(Fig. 23) both have irregularly shaped elements ods). better judge the effect of plasma-ashing
in addition to rods. Most likely these elements are on these two pollen types, additional exines, b-
derivatives of the horizontal rods; perhaps they are eluding species of Campanulaceae, were ashed and
only the free tips. Clearly, the exine structure examined in SEM. Control (nonashed) and ashed
is
more similar to that of the pantoporate species exines of Codonopsis hulleyana (Figs. 51-53),
than to the zonoporate species: elongate columellae Campanula medium (Figs. 54-56), and C. baum-
in C. angustiflora (Fig. 19) project through the garteni (Figs. 57-59) are illustrated in high-mag-
Campanula
tectum to form spinules like the pantoporate taxa nification SEMs. In the two species
plasma-ashing shows the rod-
(Fig. 22), (Figs. 56, 59) clearly
s
For purposes of comparison, species of three like substructure of the spinules as well as the
other genera of Campanulaceae are tectum. In Codonopsis hulleyana^ however, there
illustrated here:
no
Codonopsis convolvulacea Kurs (Figs. 42-44), are no spinules, and in the control there is
Githopsis pulchella Vatke (Figs. 45-47), and evidence of rods (Figs. 51, 52), xinlike in a second
39-
Wahlenhergia DC.
linarioides (Figs. 48-50). species, Codonopsis convolvulaceae (Figs.
Codonopsis convolvulacea 42-44) After plasma-ashing 60 minutes, a network
(Figs. 41). for
is
campan-
7-zonocolpate with short colpi and a tectum with (Fig. 53), not unlike the rods in typical
TEM
densely spaced rods and large spinules. In ulaceous tecta, evident. The small protuberances
is
(Fig. 44), however, distinct from most Cam- could be interpreted as vestiges of the free tip oi
it is
many
panulaceae: a well-defined endexine, no foot layer, rods. Thus the tectum of C. hulleyana (Fig-
and columellae that appear to terminate abruptly, 52) may represent a reduced stage in which the
with an outer irregular layer seemingly composed has for
identity of the rods (as well as spinules)
may
of very short columellae connected to the rods. intents and purposes, been or rep-
all lost, it
Some
inner columellae narrow at the interface and resent a primitive which these elements
state in
then become expanded again in the outer layer of have not yet become differentiated,
TEM
None
columellae. of the grains examined
in
had and
a foot-layer, the columellae extended
as
Discussion
such to the endexine. Codonopsis hulleyana For-
rest ex Diels, Figures 51 and 52, also examined For the most part our agree with those
results
TEM
in but not illustrated here, has a very gen- of Dunbar (1984), who characterized the pollen of
eralized exine structure with a definite foot layer Campanula as having bacula that "are generally
and where
simple columellae (Nowicke,
unpublished and
data), short stubble-like except one species
in
Githopsis pulchella 45-47)
(Figs. 6-7(-8)- they are high." The which she referred
is exception to
zonoporate, as in other species of the genus (Morin, ana. Dunbar, although aware ol tnc
1983), with a tectum remarkably Cam- had
similar to he pantoporate California species,
^
panula
angustiflora and them
(Fig. 1 7) C, sharsmithiae pportunity examine
(apparently)
to
(Fig. 23) in which the rods appear more The
erect. thin section,
fact that the radial section in Figure 47 somewhat The Campanula ameri-
between
is relationship
has enhanced
oblique the thickness of the foot cana and the four pantoporate California species
layer/endexine and obscured
the continuity of most perplexing. Although *'microperforate" tec-
is the
C
columellae as spinules. Other sections (Nowicke, turn of americana from the
distinguishes
it
show
unpublished) most, not very
columellae two
if all, pro- California species, all five species share
through
jecting the tectum. Note
also the resem- restricted, Campanula, poUen charac-
at least in
blance of the inner surface
of the tectum ters— col-
in the pantoporate aperture type and elongate