Pollen Morphology of Pieris D. Don (Ericaceae, Lyonieae) and Its Taxonomic Significance

10 Pages·2006·0.86 MB·English

by  A. M. K. Golam Sarwar

植物研究雑誌
J. Jpn. Bot.
81:225-234(2006)
Pollen Morphology of Pieris D. Don (Lyonieae，Er icaceae)
and Its Taxonomic Significance
A. K. M. Golam SARWA Ra and Hideki TAKAHASHIa
，b
aLaboratory of Systematic Botany，G raduate School of Agriculture，H okkaido University，
N8 W8，S apporo，0 60-8589 JAPAN;
bThe Hokkaido University Museum，N I0 W8，S apporo，0 60-0810 JAPAN
E-mail: [email protected]
(Received on November 17，20 05)
Pollen mo叩hologyof 6s pecies in the genus Pieris was examined using light and
scanning electron microscopes. Judd's infrageneric classification of Pieris was re-
examined in the light of new palynological characters. The genus Pieris is stenopalynous
in having 3-colporate and oblate pollen tetrads. However，a c ontinuous and serial varia-
tion in the exine sculpture，t etrad diameter，p ol andequatorial length of pollen and
訂
apocolpial exine thickness was revealed within the genus. Pieris nana is characterized by
having the smallest pollen and the smallest rugulae in the rugulate sculpture. Considering
other distinct morphological characters，w e confirm the recognition of the monotypic
subgenus Arcterica based on this species. Within the other subgenus，Pi eris，m embers of
the sections Pieris and Phillyreoides can be distinguished by subtle differences in colpus
width，s eptum thickness and ratio of colpus length to tetrad diameter. Pieris formosαis
distinguished by its psilate exine with clear secondary striate sculpture. Pieris japonica
and P. cubensis are not well differentiated in出epalynological characters，a nd act as a
bridge between sect. Pieris and sect. Phillyreoides. On the basis of palynological charac-
ters ad ichotomous key of these taxa was also preped.
訂
Key words: Pieris，po llen morphology，t axonomic significance.
The genus Pieris D. Don (Ericaceae- Andromedeae (Ericaceae subfamily Vac
同
Vaccinioideae-Lyonieae) (Kron et al. 2002) cinioideae). From the phenetic standpoint，
comprises seven allopatric and rather distinc- Judd (1979) did not find sufficient mo中ho-
tive species occurring in Eastem Asia， logical and anatomical distinctions between
Eastem America，a nd Cuba (Judd 1982) and the monotypic genus Arcterica and Pieris on
is closely related to several genera in the the basis of 50 selected characters，a nd
tribe Andromedeae sensu Stevens (1971). treated Arctericαnαna as an isolated species
Un til the mid of 20th century，th e generic within Pieris; P. nana (subgenus Arcterica).
limit of Pieris was not very well defined. This genus is considered to be a
Some of its species such as P. nana，P . monophyletic group easily separated from
floribunda and P. phillyreifolia we segre- related genera by an umber of features; in-
民
gated as distinct genera (Nuttall 1843，Sm all cluding the leaf aangementand anatomy，
町
1914，1 933，M akino 1961，O hwi 1965). The timing of inflorescence development，f lower，
genus Pieris，a s circumscribed by Stevens filament and spur mo中hology，seed mor-
(1971) along with the genus Arcterica Cov.， phology (Judd 1979，1 982)，c hromosome
is am ember of the Ly onia group of the tribe number， secondary metabolites (toxic
-225-
226 植物研究雑誌第81巻第4号 平成18年8月
diterpenes)，a nd molecular characters (Kron tions on pollen grains of Pieris have been
et al. 1999，20 02). However，th e infrageneric carried out previously (Yang 1952，I kuse
classification of Pieris is still in disPl!te. 1956，2 001，U eno 1962，N air 1965，H uang
Judd (1982) has divided the genus Pieris into 1972， Shimakura 1973， Nakamura 1980，
two subgenera; the monotypic subgenus Wang et al. 1995，W ei 2003). Scanning elec-
Arcterica (Cov.) Judd (including P. nana) tron microscopic (SEM) observation of pol-
and subgenus Pieris，w hich has been divided len grains has been made for only as ingle
into two sections，s ect. Pieris (including P. species， P. japonica (Kurosawa 1991).
japonica，P . formosa，a nd P. floribundlα)， Therefore，t he present study examines the
and sect. Phillyreoides Benth. & Hook. f. pollen morphology of the genus in detail
(including P. phillyreifolia，P. cubensis，a nd with the help of both LMa nd SEM to dis-
P. swinhoei). Recent combined phylogenetic cuss and review the present infrageneric
analysis of phenotypic and molecular data classification.
shows that subgenus Arcterica composed of
P. nαna is sister to the other monophyletic Materials and Methods
subgenus Pieris including P. formosa，P . The pollen of six species from the seven
floribunda and P. phillyreifolia (Kron et al. on so species in the genus Pieris was exam-
1999). But the monophyly of sect. Pieris is ined by using LM and SEM (Table 1).
not supported in the combined analysis，t hus Polliniferous material used in this investiga-
subgenus Pieris needs further study. tion was taken from dried herbarium speci-
Mainly light microscopic (LM) observa- mens from the herbaria; KYO，S ，S APS and
Table 1. Voucher specimens for the palynological studies of Pieris. LM: light microscope; SEM: scanning electron
microscope. Infrageneric classification follows Judd (1982)
Taxon Collector and number Voucher information
Subgenus Arcterica
P. nana (Maxim.) Makino Fukuda 180，1 81 (LM，S EM) Japan: Honshu，R ikuchu，M t. Hayachine，
19 June 1932 (KYO)
Takahashi & al. 2571 (SEM) Japan: Hokkaido，Pr ov. Kitami，M onbetsu-
gun，S hirataki-mura，M t. Hirayama，a lt.
1770 m，2 9 June 1982 (SAPS)
Subgenus Pieris
Sect. Pieris
P. japonica (Thunb.) D. Don Takahashi 457 (LM，S EM) Japan: Tokyo， Koishikawa Bot. Gard.，
cul ，.tpetals pink，2 3 March 1980 (SAPS)
Sasao s. n. (SEM) Taiwan: Prov. Taichu， Kantojum， 20
November 1931 (SAPS)
P. koidzumiana Ohwi Sonohara 10 (LM，S EM) Japan: Okinawa Islands， Kunigami，
Hendona，n o date (KYO)
P. formosa (Wall.) D. Don McLaren 32F (LM，S EM) China: Yunnan，P ai-ching，1 3 April 1936
(ex Herb. Hort. Bot. Reg. Edin.) (KYO)
Sect. Phillyreoides
P. phillyreifolia (Hook.) DC. Newcombe 267 (LM，S EM) USA: Georgia，C harlton Co.，O kefenokee
National Wildlife Refuge，1 3 Sept. 1982
(SAPT)
P. cubensis (Griseb.) Small Ekman (Pl. Ind. Occ. 16387) Cuba: Prov. Pinar del Rio，S ierra de los
(LM，S EM) Organos，31 March 1923 (S)
〉
ロ
m山口回同
N
o
o
a
Table 2. Variation in pollen characters of Pieris showing value (μm) and standard deviation. D: Tetrad diameter; P: Polar axis; E: Equatorial axis; minimum -maxi-
mumv alues in parenthesis. Sculpture by SEM. CR: Coarsely rugulate; CRP: Coarsely rugulate-psilate; P: Psilate. Parentheses mean indistinctness
Colpus
Name of Subgenus/ Apocolpial Septum Sculpture by
D P E(d) D/d P厄 2f/D
Section/Species Length (2f) Width exine thickness thickness SEM
旬
cd 向pum配mmiaA r c e AE也r -E c a 31.9:t1.4 17.1:t1.9 24.3:t2.5 1.31 0.70 17.3:t2.8 2.0:t0.3 0.54 2.2:t0.2 1.6:t0.3 CR*ーCR(PY*Jー* 。ロ自己
(30.0-34.6) :(14.9-20.6) (21.1-30.0) (1.15-1.42) (0.64-0.78) (13.9-21.6) (1.7-2.4) (0.45-0.63) (1.9-2.4) (1.2-1.9) 。内
Subgenus Pieris 宮
司
Sect. Pieris 自
P. japonica 42.8土2.4 22.0:t1.5 33.1:t1.4 1.29 0.66 20.2:t2.5 1.6:t0.6 0.47 2.4:t0.3 1.1:t0.3 CR-CR(Py*J 20
(39.3-46.2) (19.5-24.4) (31.4-36.0) (1.14-1.41) (0.60-0.74) (16.5-24.8) (0.7-2.5) (0.36-0.58) (2.1-3.0) (0.7-1.5) 回
。
P. koidzumiana 39.3:t2.1 21.4:t1.6 29.7:t1.5 1.32 0.72 16.9:t2.8 1.6:t0.5 0.43 2.6:t0.3 1.7:t0.2 CR-CRP(*J 冨ロ
〕
(37.4-42.7) (19.0-23.5) (27.1-31.2) (1.23-1.40) (0.65-0.78) (13.4-20.6) (0.7-1.9) (0.36-0.54) (2.2-2.9) (1.4-2.2) 『
〈
P. formosa 41.5:t2.6 22.1:t1.4 30.5:t2.5 1.36 0.72 13.8:t1.2 2.0:t0.3 0.33 2.1:t0.2 2.2:t0.2 p* 。
戸
(37.2-45.6) (19.9-27.7) (27.8-34.8) (1.28-1.45) (0.65-0.81 ) (12.5-16.8) (1.4-2.4) (0.27-0.45) (1.9-2.4) (1.9-2.4) ∞
H
Sect. Phillyreoides
Z
P. phillyreifoliα 48.6士1.6 24.3:t2.0 35.6:t2.2 1.37 0.68 29.0:t2.8 0.7:t0.3 0.6 1.9土0.5 1.0:t0.4 CRP* 。・ム
(47.0-51.2) (20.8-27.7) (32.2-39.6) (1.26-1.49) (0.62-0.74) (24.8-33.0) (0.5-1.5) (0.53-0.64) (1.3-2.8) (0.5-1.7)
P. cubensis 39.3:t1.2 20.8:t1.0 30.7:t1.2 1.28 0.68 18.6:t1.4 0.6:t0.l 0.47 2.3:t0.3 0.7:t0.2 CRP*
(38.0-41.3) (19.8-22.8) (29.4-33.0) (1.24-1.33) (0.63-0.72) (17.3-21.4) (0.5-0.8) (0.42-0.52) (2.0-2.8) (0.5-1.2)
*Secondary striate sculpture distinct
M
M
J可
228 植物研究雑誌第81巻第4号 平成18年8月
Table 3. Cumulative variance and eigen vectors of principal component analysis (PCA) using ten palynological
characters based on LMf or six species of Pieris. Character abbreviations corresponding to Table 2
Principal component axis 2 3
Cumulative variance (%) 39.926 60.622 76.138
Characters Eigen vectors
D 0.417 0.336 -0.030
P 0.355 0.437 -0.149
E( d) 0.432 0.186 -0.297
D/d -0.024 0.337 0.579
P厄 -0.155 0.460 0.230
Colpus length (2t) 0.416 -0.118 0.364
Colpus width -0.363 0.067 0.110
2fID 0.228 -0.378 0.465
Apocolpial exine thickness -0.185 0.032 -0.353
Septum thickness -0.312 0.416 0.126
SAPT (the Botanic Garden， Hokkaido Quantitative data of pollen morphological
University，S apporo). features (first ten characters shown in Table
Pollen was acetolysed following the tech- 2) were used for statistical calculations of
nique of Erdtman (1960) modified by total similarities between the pollen grains of
Takahashi (1987). For LM，th e pollen was six species with principal component analy-
mounted in silicone oil (viscosity 3000 cs)， sis (PCA) using the Excel Stat computer
and examined and measured with aN ikon package.
Eclipse E 200 microscope. The dimensions
“D"，“Pぺ“E(d)" and “2f'，c oespondingto Results
町
the tetrad diameter，p olar length，e quatorial General pollen morphology of Pieris
diameter and colpus length of pollen grain， Light microscopy observations: pollen
were measured，a nd the D/d，P Aa nd 2fID grains united at tetrahedral tetrad (Fig. 1)，
ratios were calculated (see Oldfield 1959). relyother configurations，v iscin threads
紅
The measurements given in Table 2 are absent，si ze medium，or minute in P. nanα，D
based on at least 10 grains from each speci- 31.9-48.6μm，P 1 7.1-24.3μm，E 2 4.3-35.6
men. Pollen size and shape classes follow 阿n，P厄 0.66-0.72，ob late in shape，ra tio of
Erdtman (1986). Pollen slides of all collec- tetrad diameter to individual grain diameter
tions are deposited at the Hokkaido (D/d) 1.28-1.37， 3-aperturate， apertures
University Museum，S apporo，J apan. For 訂ranged according to “Fischer乍 Law"，
SEM，t he acetolysed pollen samples were colporate，c olpi distinct (Fig. 2)，1 3.8-29.0
dehydrated in an ethanol series，a nd mounted 阿nlong，w idth 0.6-2.0阿n，ratio of colpus
and air dried on aluminum stubs from 70 % length to tetrad diameter (2flD) 0.33-0.60，
ethanol，a nd sputter coated with Platinum- wider at middle，s omewhat obtuse to acute
Palladium or Gold-Palladium by aH ITACHI towards ends，co lpus m gindistinct，or a dis-
訂
EI02 ion sputter. Subsequently the prepared tinct，la longate，1. 0-3.0μm long，w idth 6.4-
pollen was examined and photographed with 11.0μm，c ostae present but not clear in P.
aJ EOL JS乱ι5310LVscanning electron mi- phillyreifolia and P. japonica，e xine tectate，
croscope operated at 15 KV. Descriptive ter- apocolpial exine 1.9-2.6阿nthick，s eptum
minology follows Punt et al. (1994). thickness 0.7-2.2阿n，apocolpial exine com-
August 2006 Journal of Japanese Botany Vol. 81 No. 4 229
Figs. 1--4. SEM rnicrographs of pollen grains in Pieris species. 1: Pollen tetrad at pol view(P.
征
formosa). 2: Pollen tetrad at equatorial view showing aperture (P. formosa). 3--4: Apocolpial exine
sculpture of P. nana (Takahashi & al. 2571 and Fukuda 180，re spectively).
monly thicker than septum except P. cies occupy each distinct range，s o we can
formosa with thicker septum. Exine sculp- generally compare the palynological features
ture commonly veucateto finely rugulate of six Pieris species in this analysis (Fig.
町
or rugulate in P. cubensis，P . phillyreifolia 11).
and P japonica，o r coarsely veucateto
汀
co sely rugulate in P. formosa， P. Pollen characteristics of Pieris
紅
koidzumiana and P. nanα. Subgenus Arcterica (monotypic， species
SEM Observations: apocolpial exine examined: P. nana)
sculpture various from coarsely rugulate to Pollen grains few in number at both LM
psilate，t he rugulae with secondary sculp- slide and SEM stub. Pollen surface uneven
tures; faintly to finely and clearly striate and rugged， exine sculpture coarsely
(Figs. 3-10). Exine sculpture along the colpi rugulate，th e rugulae faintly (Fig. 3) to finely
similar to that appe ingat distal pole，b ut striate (Fig. 4). In PCA，P. nana is situated at
紅
mesocolpial exine having a tendency to the lower left edge of total variation of the
decrease in lateral extension of the rugulae Pieris pollen (Fig. 11).
with more distinct units，c olpus membrane
granular to granuloid. Subgenus Pieris
In principal component analysis (PCA) Section Pieris (species examined: P. japon-
using the LMc haracters，do ts from each spe- ica，P . koidzumiana and P. formosα)
230 植物研究雑誌第81巻第4号 平成18年8月
Figs. 5-10. SEM micrographs of apocolpial exine sculpture in Pieris species. 5-6: P. japonica
(Takahashi 457 and Sasao s. n.，re spectively). 7: P. koidzumiana. 8: P. formosa. 9: P. phillyrei-
folia. 10: P. cubensis.
Colpus membrane coarsely granulate in P. along with P. cubensis of Sect. Phillyreifolia.
japonica. Pollen surface uneven to somewhat Among the species P. formosa shows the
flaf and rugged，e xine sculpture coarsely highest value in the second component (Fig.
rugulate，t he rugulae faintIyt o finely striate 11).
in P. japonica and P. koidzumiana (Figs. 5-
7) to psilate with clearly striate sculpture in Section Phillyreoides (species examined: P.
P. formosa (Fig. 8). In PCA，m embers of this phillyreifolia and P. cubensis)
section fall in the middle of total variation， Most grains shrink somewhat in P.
August 2006 Journal of Japanese Botany Vo .l81 No. 4 231
Legend:
6P. nana
4 く>P. japonica
• P. koidzumiana
。 oP.formosa
-P. phillyreifolia
3 。 。 • P. cubensis
。
。
2 08 。
-・.
•
省 且
NE30. 。•
邑
5 、 。
• 。
目
•
• ・.•
1:1.
企
J
~.<>
企 A
幽2 1:1.1:1. 1:1.-1 •
A 。
1:1.
-3 。
4 -3 -2 2 3 4 5 6
Component 1
Fig. 11. Two dimensional diagram of component 1a nd 2o f pollen grains of six Pieris spe-
cies based on principal component analysis using ten palynological characters.
phillyreifolia. Pollen surface uneven and rug- group of closely related entities. However，
ged， exine sculpture coarsely rugulate SEM observations show av ariation in exine
(-p silate)，t he rugulae loosely arranged，a nd sculpture within the genus (Figs. 3-10).
finely and clearly granulate-s仕iatein P. There is am ore or less continuous and serial
phillyreifoliα(Fig. 9) or striate in P. cubensis variation in the exine sculpture from co sely
紅
(Fig. 10). In PCA，P. phillyreifolia is situated rugulate through co selyrugulate-psilate to
紅
at the right edge of total variation of the psilate，a mong the Pieris species.
Pieris pollen which shows the highest value Pieris nana has the smallest pollen tetrad
of the first component and P. cubensis pollen (D = 31.9伊n)and the smallest rugulae in
could not be separated from P. japonica pol- size (compare Figs. 3-4 and 5-10). This spe-
len (Fig. 11). cies has also very distinctive morphological
characters viz. low shrub with small，en tire
Discussion and usually whorled leaves， roughened-
All species of Pieris examined in this papillose filament，a nd anthers with poorly
study have 3-colporate and oblate pollen tet- developed disintegration tissue etc.，di ffering
rads having similar rugulate to rugulate- from the other species of the genus (Judd
psilate (rarely psilate) exine with secondary 1982). The low number of pollen grains in
striate sculpture，w hich suggests that the both LMs lide and SEMs tub might be due to
genus including P. nana is，a s aw hole a the presence of poorly developed disintegra-
232 植物研究雑誌第81巻第4号 平成18年8月
tion tissue in anthers，or all specimens might Ericaceae (Warner and Chinappa 1986).
have been collected at very late flowering These two palynological characters might be
stage. The distinctiveness of the P. nana pol- of special taxonomic importance in
len is also supported by PCA (lower left Ericaceae. Distinct differences have also
edge of total variation) using 10 been found in apocolpial exine and septum
palynological characters based on LMo bser- thickness between the two sections (Table
vations (Fig. 11). The PCA also indicates 2): sect. Pieris have comparatively thicker
that among the remaining five species，P. ja- apocolpial exine and septum (2.1-2.6阿n
ponica，P . koidzumiana，P. formosa and P. and 1.1-2.2阿ll，respectively) than those of
cubensis are relatively closer together and the sect. Phillyreoides (1.9-2.3μm and 0.7-
situated at the middle of total variation，a nd 1.0μm，re spectively).
P. phillyreグoliaalso has ad istinct (right- Judd (1982) considered P. japonica as a
hand most) position (Fig. 11). This results of variable species; it includes a number of
PCA support the division of the genus Pieris synonyms at the species level，e . g.，P .
into two subgenera; the monotypic subgenus popowi Palibin，P . tαiwanensis Hayata，P .
，
Arcterica (including P. nana) and the other polita W. W. Sm. & Jef frey，P. koidzumiana
subgenus Pieris composed of the remaining Ohwi. Pieris koidzumiana occupies the inter-
species. The infrageneric classification of mediate space between P. japonica and P.
Pieris proposed by Judd (1982) is generally formosa in PCA (Fig. 11). But in exine
supported by the palynological characters， sculpture P. koidzumiana (Fig. 7) is more
with some exceptions viz. P. cubensis of similar to P. japonicα(Figs. 5-6) than P.
sect. Phillyreoides shows ac loser relation- formosa (Fig. 8). Thus palynological charac-
ship with the members of sect. Pieris ters do not positively support the separation
(especially P. japonica) (Fig. 11). of P. koidzumiana from P. japonica. Judd
Within subgenus Pieris，P 厄 ratioshows a (1982) also did not confirm the species status
difference between the two sections (Table of P. koidzumiana，b ecause he did not find
2). Section Pieris possesses a relatively any clear gap between P. koidzumianαand
larger value (0.72) of P厄， and sect. P. japonica in leaf shape or marginal denta-
Phillyreoides possesses the smaller value tion，a lthough he recognized some distinct
(0.68)，ex cept for P. japonica of sect. Pieris morphological differences between them.
that has the P厄 value0.66，ev en lower than However，c onsidering other distinctions in
sect. Phillyreoides. Colpus length，w idth and the morphological characters of P.
ratio of colpus length to tetrad diameter koidzumiana: e. g. the leaves oblanceolate
(2flD) show distinct differences among the with more blunt tip， rachis densely
species (Table 2). Pollen grains of the sect. puberulous，fl owers longer etc. compared to
Pieris possess comparatively smaller but those of P. japonicα(Yamazaki 1993)，it is
wider colpus (13.8-20.2μm and 1.6-2.0阿ll， better to separate P. koidzumiana from P.
respectively) compared to those of the sect. japonica as ad istinct species，en demic to the
Phillyreoides (18.6-29.0問IIand 0.6-0.7μm， Ryukyu Islands，J apan.
respectively). The 2fID value is relatively Neither the close relationships between P.
smaller (0.33-0.47) in the sect. Pieris，a nd japonica and P. formosa， nor P.
larger (0.47-0.60) in the sect. Phillyreoides. phillyreifolia with P. cubensis and P. jαpon-
Distinct differences in P厄 and2fID ratios ica，w hich were found in morphological and
were also reported previously among the sec anatomical characters (Judd 1982)，is sup-
田
tions of the genus Enkianthus (Sarwar and ported by our palynological observations
Takahashi 2005) and different subfamilies of (Figs. 5-11). However，P. japonica pollen
August 2006 Journal of Japanese Botany Vol. 81 No. 4 233
can not be separated from that of P. cubensis ...・...P. koidzumiana
in PCA (Fig. 11)，a nd the exine sculpture is 3b. D/d 1.36，2 fID 0.33，s eptum thicker
also similar between. the two species (Figs. than distal exine，s eptum thickness 2.2
5-6 ，10 ). Pieris japonica and P. cubensis act 阿n，pollen surface somewhat flat，
as ab ridge between the two sections Pieris exine sculpture psilate with clearly
and Phillyreoides. A close relationship be- secondarily striate ・... ・-…..P.formosa
H
tween P. formosa and P. phillyreifolia sug- 2b.2flD 0.47-0.60，c olpus width 0か 0.7
gested by Kron et al. (1999) was not μm，s eptum relatively thinner (0.7-1.0
supported by PCA (Fig. 11)，bu t the distinct- 阿n)・…...・ ・.....・ ・......・ ・....・ ・...・ ・...・ ・.5
H H H H H H
ness of secondary striate sculpture is com- 5a. D/d 1.37，2 fID 0.60，s eptum thickness
mon palynological feature between these two 1.0μm，t he rugulae finely and clearly
species (Figs. 8-9). Under SEM，P. formosa granulate-striate ・... ・.P. phillyreifolia
H
is readily distinguished by its psilate exine 5b. D/d 1.28，2 fID 0.47，s eptum thickness
with clear secondary striate sculpture (Fig. 8) 0.7阿n，the rugulae finely and clearly
among Pieris species. Other species have a striate ・... ・.....・ ・..…...・ ・...P. cubensis
H H H
serial variation in the co selyrugulate-
紅
psilate exine sculpture (rugulae faintly to Authors wish to express their sincere
finely striate). Further research including the thanks to the Directors and Curators of her-
study of more specimens and combined baria: KYO，S ，S APS and SAPT for allow-
analysis of mo中hologicaland molecular ing us to examine and/or send the specimens
data from other regions is needed to clarify on loan and sample polliniferous materials.
the relationships among the Pieris species. Particular thanks are due to Mr. Toshiaki Ito
of Electron Microscopy Laboratory ，
Key to the species of Pieris based on Graduate School of Agriculture，H okkaido
pollen morphology University for his technical assistance and
1a. Pollen grains minute，p ollen surface un- cooperation during the SE乱1:study and pho-
even and rugged， exine sculpture tography of pollen grains. The first author
co selyrugulate，t he rugulae smallest (A.K
紅
..P. nana Ministry of Education， Culture， Sports，
1b. Pollen grains medial，p ollen surface un- Science and Technology (MEXT) for
even and rugged to somewhat flat，e xine Monbukagakusho Scholarship during the pe-
sculpture coarsely rugulate to psilate，th e riod of this study.
rugulae relatively larger ・... ・...・ ・...・ ・..2
H H H
2a. 2fID 0.33-0.47，c olpus width 1.6-2.0 References
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A. K. M. ゴラムサルワlレa，高橋英樹b.アセビ
属(ツツジ科ネジキ連)の花粉形態と分類学的意
義 認めることを支持する.残りのアセビ亜属 Pieris
アセビ属Pieris約7種のうち 6種の花粉形態を 内の， Pieris節と Phi11yreoides節とは溝の幅，四
光学顕微鏡と走査型電子顕微鏡で観察し， Juddの 集粒内の花粉粒間壁厚，四集粒径に対する溝長の
属内分類体系を花粉形態形質から再検討した.ア 比率で微妙な差がある.P. formosaは明瞭な二次
セビ属はステノパリナス(花粉の形態変異幅が狭 的縞模様を持った平滑型の花粉彫刻模様により識
いこと)で，偏球形の 3溝孔粒からなる四集粒花 別される.アセビP.japonicaとP.cubensisとは
粉であった.それでも属内には，花粉壁の彫刻紋 花粉形質では十分に区別することができず， Pieris
様，四集粒径，極軸・赤道軸長，遠心極域の壁厚 節と Phi11yreoides節とを結ぶ位置を占めている.
において連続的な変異があった.この中でコメパ 花粉形態形質によるこれら分類群の検索表を作成
ツガザクラ P.nanaは最も小さいサイズの花粉粒 した.
を持ち，花粉壁のしわ紋様の単位も最小で，他の (a北海道大学農学研究科植物体系学研究室，
明瞭な外部形態形質を考えあわせると，本種1種 b~じ海道大学総合博物館)
からなる単型のコメバツガザクラ亜属Arctericaを