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Flora 202 (2007) 570–580
www.elsevier.de/flora
Achene morphology and slime structure in some taxa of Artemisia L.
and Neopallasia L. (Asteraceae)
Agnieszka Kreitschitza,, Joan Vallèsb
a
Division of Plant Morphology and Development, Institute of Plant Biology, University of Wrocław, Kanonia 6/8,
50-328, Wrocław, Poland
b
Laboratori de Botànica, Facultat de Farmàcia, Universitat de Barcelona, Av. Joan XXIII s/n, 08028 Barcelona, Catalonia, Spain
Received 18 August 2006; accepted 21 December 2006
Abstract
We have examined slime cell distribution on the surface of the achenes of some Artemisia and Neopallasia taxa, as
well as slime composition, envelope formation during the hydration, and slime relation to different morphological
features and environmental factors. The results of the studies show a characteristic pattern of slime cells distribution,
which could differ between taxa. The slime in the taxa studied belongs to the cellulose type and consists of two
components i.e., pectins and cellulose. Although all fruits contain slime cells, not all of them show the slime envelope
formation. Plants occurring in dry habitats (such as A. barrelieri) or annual species (such as A. annua) are characterised
by a large amount of slime and a fast process of slime envelope formation. Slime production has not been observed in
some polyploid populations (A. campestris and A. campestris ssp. sericea) and in two species occurring in relatively
fertile habitats (A. verlotiorum, A. vulgaris). A reason for this may be either the immaturity of polyploid fruits leading
to the production of a scarce, not detectable slime amount or, alternatively, the occurrence of not functional slime cells.
Slime facilitates and stimulates the germination, as well as the adherence of the fruits to the ground or to animals (for
dispersal). The slime could play important role in the distribution and colonisation of new habitats in many Artemisia
taxa.
r 2007 Elsevier GmbH. All rights reserved.
Keywords: Achene; Slime cells; Cellulose slime; Pectins; Asteraceae
Introduction
Morphological and anatomical studies on the fruit
and seed structure play an important role in systematics.
Microstructural details of the seed and fruit coat make
possible the distinguishing of taxa or the discovery of
their affinities. This is especially useful in families in
which identification of particular taxa is complicated,
Corresponding author. Fax: +48 71 3754118.
E-mail addresses: skowron@biol.uni.wroc.pl (A. Kreitschitz),
joanvalles@ub.edu (J. Vallès).
0367-2530/$ - see front matter r 2007 Elsevier GmbH. All rights reserved.
doi:10.1016/j.flora.2006.12.003
e.g. in Portulacaceae, Scrophulariaceae, Polemoniaceae,
Caryophyllaceae and Orobanchaceae (Johnson et al.,
2004; Plaza et al., 2004; Zeng et al., 2004). Furthermore,
observations of micromorphological features can also
provide us with information about developmental
strategies, adaptation to different environmental conditions and evolutionary tendencies within related groups
of plants (Johnson et al., 2004; Plaza et al., 2004; Zeng
et al., 2004).
The presence of slime has been reported in diverse
groups of organisms such as bacteria, algae, fungi,
lichens and mosses (Mühlethaler, 1950). Slime is also
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widespread in higher plants, especially in fruits and/or
seeds in families such as Brassicaceae, Euphorbiaceae,
Plantaginaceae, Linaceae, Malvaceae, and Lamiaceae
(Baiges and Blanché, 1988; Huang et al., 2000;
Mühlethaler, 1950; Western et al., 2000; Wojciechowska, 1961, 1966; Young and Evans, 1973). Within the
Asteraceae family, slime has been reported, among
others, in Filifolium (Mouradian, 1995), Achillea,
Anthemis, Chrysanthemum (Grubert, 1974) and Artemisia (Boyko, 1985; Grubert, 1974; Huang and Gutterman, 1999a, b; Huang et al., 2000; Korobkov, 1973;
Mouradian, 1995; Oganesova, 1981; Yakovleva et al.,
2002).
Pectins are the major component of slime, which
is also present in all cell walls, mainly in the middle
lamella. Pectins are mostly acidic polysaccharides
with a special capacity for hydration. After wetting
of dry mucilaginous seeds, the slime is released and
forms a gel envelope (Fahn and Werker, 1972; Western
et al., 2000). The classification distinguishes ‘‘true
slime’’, consisting of pectins e.g. in Linum usitatissimum
or Plantago psyllium, and cellulosic slime e.g. in Cydonia
vulgaris and Salvia spp. (Frey-Wyssling, 1959;
Mühlethaler, 1950). The latter type is characterised by
the presence of an additional cellulosic skeleton,
forming helicoidal thickenings, as in seeds of Cobea
scandens (Fahn and Werker, 1972; Frey-Wyssling,
1959). Slime can be deposited between plasmalemma
and the primary cell wall in the last stage of protoplast
lifetime and then it dries out with fruit ripening.
Slime formation can also result from secondary modifications occurring in the cell wall (Fahn and Werker,
1972).
Different functions have been reported for slime. It
plays an important role in the control of germination,
mostly in plants that grow in the condition of water
deficiency in arid and semiarid environments, thus
facilitating imbibing and maintenance of the water. It
can also delay germination due to impeded penetration
of the oxygen. Slime helps in fruit or seed dispersal and
in the defence against pathogens (Fahn and Werker,
1972; Huang and Gutterman, 1999a, b; Huang et al.,
2000; Korobkov, 1973; Young and Evans, 1973; Young
and Martens, 1991).
Artemisia is one of the biggest and the most widely
distributed genus of the Asteraceae family, occurring
mostly in the Northern Hemisphere. Depending on the
authors, it contains from 200 to ca. 500 species (Vallès
and Garnatje, 2005 and references therein; Vallès and
McArthur, 2001), including various life forms such as
perennial shrubs and biennial or annual herbs. Most
Artemisia taxa dominate in steppes, deserts or semideserts of Eurasia, North America and North Africa
(Bremer, 1994; Gams, 1987; Polyakov, 1995; Vallès
and McArthur, 2001; Żukowski, 1971). Many of them
are common weeds; some are also used as food,
571
medicinal and ornamental plants. Neopallasia is an
Asian monotypic genus segregated from Artemisia
(Polyakov, 1995).
The wide range of geographical distribution and
variety of habitats in which Artemisia occurs may
result in different adaptations to diverse environments.
Adaptive features may be manifested by the changes
in morphology and anatomy of different plant organs
as well as in the cell structure and function, exemplified
by the increase of ploidy level and nuclear DNA
content (Garcia et al., 2004; Torrell and Vallès, 2001).
Another important adaptive feature may be the slime
presence in the fruits (Huang et al., 2000; Korobkov,
1973).
Achenes of Artemisia are small, pappus lacking,
ovoid to ellipsoidal in shape, thin-walled and usually
glabrous but occasionally with some trichomes. Rows of
myxogenic (mucilage-, slime-producing) cells can be
present on the achene surface (Bremer, 1994). Some
results on Artemisia achene sculpture have already been
published (Korobkov, 1973; Ouyahya and Viano, 1984,
1990; Vallès and Seoane, 1992), but there is very scarce
information on achene slime (Yakovleva et al., 2002)
and almost no data on slime structure. The aims of this
work have been (1) to examine the distribution of the
slime cells on the achene surface, with possible
differences between taxa, (2) to discern the slime
structure, its composition and its formation after
hydration and (3) to determine the relationship between
slime presence and habitats, plant life form and
ploidy level.
Material and methods
Plant material
Achenes of 12 Artemisia and one Neopallasia taxa
were used for the analysis of achene surface morphology
and slime characteristics. Mature achenes were collected
from natural plant populations. Plant vouchers are
deposited in the herbaria of either A. Kreitschitz
(Wrocław) or the Centre de Documentació de Biodiversitat Vegetal de la Universitat de Barcelona (BCN) or
the Shrub Sciences Laboratory, Provo, UT (SSLP). The
list of taxa, locations and collectors are presented in
Table 1.
Scanning electron microscopy (SEM)
The sculpture of the achene surface was analysed on
the SEM. Dry, mature achenes were mounted directly
on the stubs using double-sided adhesive tape, coated
with gold particles, and then observed in the SEM (JSM
5800LV JEOL and LEO435VP).
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Table 1.
A. Kreitschitz, J. Vallès / Flora 202 (2007) 570–580
Location of the plants studied
Taxon
Genus Artemisia
Subgenus Artemisia
A. annua L.
A. biennis Willd.
A. verlotiorum Lamotte
A. vulgaris L.
Subgenus Absinthium
A. absinthium L.
Subgenus Dracunculus
A. dracunculus L.
A. campestris L. (2 )
Location
Collector, date and herbarium
Wrocław, Rzeszów (Poland)
Rzeszów (Poland)
Fogars de Tordera (Catalonia, Spain)
Wrocław, Chrza˛ stawa Mała,
Bolesławiec, Sobieszów (Poland)
Kreitschitz (2003), AK
Oklejewicz (2004), AK
Oklejewicz (2004), AK
Vallès (1998), BCN
Kreitschitz (2004), AK
Czeszów (Poland)
Kreitschitz (2004), AK
Wrocław (Poland)
Oriola,
Aranjuez (Spain)
Żagań
Brzezia Ła˛ ka, Ludgierzowice, Milicz,
Miłochowice (Poland)
A. campestris L. ssp. sericea (Fr.)
Lemke and Rothm.
Grzybowo,
Ustka, Darłówko (Poland)
Kreitschitz (2004), AK
Torrell and Vallès (1996), BCN
Gómez and Vallès (1994), BCN
Da˛ browska (2002), AK
Kreitschitz (2004), AK
Kreitschitz (2004), AK
Kreitschitz (2004), AK
Klimczyńska (2002), AK
Kreitschitz (2004), AK
Subgenus Seriphidium
A. barrelieri Besser
Oriola (Spain)
Vallès (1994), BCN
Subgenus Tridentatae
A. nova Nelson
A. pygmaea A. Gray
Utah (USA)
Utah ( USA)
McArthur (2004), SSLP
McArthur (2004), SSLP
Genus Neopallasia
N. pectinata (Pallas) Poljakov
Ulaan Baatar (Mongolia)
Vallès (2004), BCN
A. campestris L. (4 )
Slime identification by chemical reactions
Microchemical reactions for cell wall components
were carried out to identify the slime type. The following
reagents were used: 0.1% aqueous solutions of methylene blue, ruthenium red, iodine in potassium iodide
with sulphuric acid (I in KI+H2SO4), zinc chloroiodide
(ZnClI) and alcohol solution of safranin (Braune et al.,
1975; Broda, 1971; Filutowicz and Kużdowicz, 1951;
Gerlach, 1972; Western et al., 2000). The images were
taken using a light microscope OLYMPUS BX-50
connected with a SONY 3CCD colour video camera
and graphic station Indy (SGI).
Results
Sculpture of achene surface
The achene surface in all studied taxa but A. campestris
ssp. sericea is glabrous and glossy. In A. campestris ssp.
sericea long single trichomes occur on one end of the
achene. They are fragile, easy to detach. The most
external part of the fruit coat (achene coat) consists of
two different types of cells, i.e. proper epidermal cells
(Figs. 1–3B) and slime cells (Figs. 1–3A, B, C, Fig. 4K).
Due to their arrangement, the achene surface is roughly
sulcate.
The proper epidermal cells formed ribs parallel to the
long axis of the achene. These ribs can be evident as
relatively wide strands (Figs. 1D, E, 2M), individual ribs
(Figs. 1B, 2I) or separated cells (Fig. 2J). Sometimes the
contours of the ribs can be very faintly marked, giving a
smooth surface e.g. in A. absinthium (Fig. 1A).
Much smaller than proper epidermal cells are the
slime cells, here usually rectangular (Fig. 2M). They
could be more irregular, oval to ovate or triangular, as
in A. nova and A. pygmaea (Figs. 2K, 3B, C, 4K). Slime
cells form ladder-like columns that are elongated in a
parallel plane to the long axis of the achene. Ladder-like
groups of slime cells can either evenly cover almost the
entire surface of the achene, as in A. barrelieri and
Neopallasia pectinata (Figs. 1C and 2N), or alternate
with strands of the proper epidermal cells e.g. in
A. absinthium, A. biennis and A. vulgaris (Figs. 1A, D
and 2M). The surface of slime cells can be smooth
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Fig. 1. (A–H) Achene surface showing the distribution of proper epidermal cells and slime cells; (A) Artemisia absinthium, (B)
A. annua, (C) A. barrelieri, (D) A. biennis, (E) A. campestris (diploid: 2n ¼ 2x ¼ 18), (F) A. campestris (tetraploid: 2n ¼ 4x ¼ 36,
achene from Brzezia Ła˛ ka locality), (G) A. campestris (tetraploid: 2n ¼ 4x ¼ 36, achene from Ludgierzowice locality) and (H)
A. campestris ssp. sericea (tetraploid: 2n ¼ 4x ¼ 36, locality Grzybowo). White arrows indicate the proper epidermal cells, which
occur as a smooth strips (A), ribs (D) or narrow individual cells (E). Black arrows show the slime cells, which are arranged in
‘‘ladder-like’’ strips: A, D, E, F and G. On the surface of the slime cells are visible delicate ripples (A–C, E). White arrows show the
proper epidermal cells, black arrows – the slime cells.
: cells are between arrows,
: arrow shows the cell.
(e.g. in N. pectinata – Fig. 2 N) or with delicate ripples as
in A. absinthium or A. dracunculus (Figs. 1A, 2I). A
distinct pattern occurs in A. nova achenes, where slime
cells form small groups (Figs. 2J, 3B, 4K) scattered over
the achene surface between proper epidermal cells. Both
types of cells are evenly spaced along the long axis of the
achene.
The arrangement of the cells is rather the same in
all studied taxa except A. nova, where the slime cells
form short arrays (groups instead of long columns)
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Fig. 2. (I–P) Achene surface showing the distribution of proper epidermal cells and slime cells; (I) A. dracunculus, (J) A. nova, (K)
A. pygmaea – the slime cells of irregular shape, (L) A. verlotiorum, (M) A. vulgaris, (N) N. pectinata; (O, P) cross section through the
achene-the slime cells with a layer of slime-(O) A. absinthium and (P) A. campestris (tetraploid, locality Żagań), arrows show the
thick layer of slime; white arrows show the proper epidermal cells, black arrows – the slime cells;
: cells are between arrows,
: arrow shows the cell.
distributed among proper epidermal cells. In all the
studied taxa, the differences concern particularly the
form of the surface (smooth, with ripples or with folds,
size of columns and cells), suggesting possible specific
patterns for the different taxa. Further studies with a
larger sampling might confirm whether these features
could be useful for taxonomic purposes.
Slime characteristics
In the slime cells, a thick layer of slime is present
(Fig. 2O, P). The Artemisia slime was determined to
belong to the cellulose type. This type of slime represents
a heterogenous system made of a pectinous matrix and a
cellulose skeleton (Table 2). The presence of these
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Fig. 3. (A–I) The slime cells, staining results and slime formation. (A) A. verlotiorum, (B) A. nova and (C) A. pygmaea-the slime cells
of irregular shape, (D) A. annua pink, homogenously stained pectins are building a slime envelope, (E) N. pectinata – the beginning
of staining, (F) N. pectinata very long cellulose threads (black arrows), (G) A. barrelieri, (H) A. campestris (tetraploid: 2n ¼ 4x ¼ 36,
locality Brzezia Ła˛ ka) the coiled cellulose thread, (I) A. annua cellulose strands (black arrow). (A–C) slime cells without staining,
after hydration, green arrows indicate the slime cells, (D–G) staining with ruthenium red (pectins detection), (H–I) staining with
safranine (pectins detection).
components was detected based on microchemical
reactions. Treatments with different dyes revealed a
characteristic staining pattern, this being in agreement
with results known from literature (Table 2).
Ruthenium red revealed a pink envelope around the
achene (Fig. 3D–G). A red or orange–red coloration of
slime was obtained with safranine (Figs. 3H, I, 4K).
Methylene blue gave a very faint blue or almost
undetectable colour; this metachromatic dye is also
often used for cellulose identification, therefore results
can be ambiguous.
Cellulose was identified with four microchemical reactions (Table 2). Staining with ZnClI resulted in a delicate
violet coloration of cellulose strands. In I in IK (Fig. 4L)
and methylene blue (Fig. 4M–O) the cellulose strands were
stained in blue. Staining reactions with ZnClI and I in IK
are specific for cellulose detection, and also characteristic
of cellulosic slime identification (Mühlethaler, 1950). A red
(red–orange) colour of cellulose strands was obtained with
safranine (Figs. 3H, I, 4J). Although the same colour was
observed in the case of pectin staining, here the structural
aspects of cellulosic strands were clearly visible, whereas
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Fig. 4. (J–R) Staining results and slime formation. (J) A. campestris (diploid: 2n ¼ 2x ¼ 18), (K) A. nova irregular shape of the slime
cells, (L) A. campestris ssp. sericea (tetraploid: 2n ¼ 4x ¼ 36, locality Grzybowo), (M) A. annua, (N) A. biennis, (O) A. campestris
(diploid 2n ¼ 2x ¼ 18), (P–R) N. pectinata, the beginning of the slime cell hydration (green arrows), (R) uncoiling of the cellulose
threads (black arrows). (J, K) staining with safranine (cellulose detection), (L) I in IK+H2SO4 cellulose detection, (M–O) staining
with methylene blue (cellulose detection). Black arrows indicate cellulose threads.
pectin colour was spread homogenously within the
envelope. Cellulose forms relatively thick helicoidal strands
that after hydration can partially or entirely uncoil. After
unwinding, these strands assume the shape of long,
straight threads (Fig. 4M–O) forming a characteristic
radial skeleton around the achene.
Swelling and slime envelope formation
Proper epidermal and slime cells form a transparent,
delicate layer about 1–6 mm thick (Fig. 2O, P). This film
can adhere tightly to the achene (e.g. A. vulgaris,
A. verlotiorum) or enclose it loosely, forming a gap
between the achene surface and the envelope. In the
latter case, it makes for easy removal of the envelope, as
in A. nova and A. pygmaea.
The first step of the slime envelope formation is the
swelling of pectin component of the slime (Fig. 4P).
Then, the cell wall is perforated as a result of the
increased pressure and the mucilaginous content is
discharged (Fig. 4Q, R). Cellulose strands can remain
coiled (A. absinthium, A. dracunculus) or, conversely,
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Table 2.
577
Slime staining
Staining
Target
Obtained
colour
Literature data
References
Ruthenium red
Pectin
Pink
Pink, carmin-red, red
Safranin
Pectin
Methylene blue
Cell wall
Pectin
Red, orangered
Red
Not detected
Brown to orangeyellow
Red
Blue
Western et al. (2000); Filutowicz and
Kużdowicz (1951); Gerlach (1972); Broda
(1971)
Gerlach (1972)
ZnClI
Cellulose
Cellulose
Blue
Violet
Violet, blue
Violet, blue, dark blue
I in IK+H2SO4
Cellulose
Dark blue
Dark blue to dirty
blue
Blue
uncoil into the shape of long threads (Fig. 4M–O).
Cellulose threads are usually shorter than the width of
the achene. Only in Neopallasia uncoiled threads can be
3–4 times longer than the achene width, which is very
characteristic of this genus (Fig. 3F).
The process of swelling can be rapid, triggered
immediately after wetting of the achene, e.g. in A. annua,
A. barrelieri and N. pectinata. In some taxa, envelope
formation last several minutes up to a few hours, e.g. in
A. dracunculus and A. nova.
Variation in slime envelope formation
Although the slime cells are present in all studied taxa,
swelling was not observed at all in A. vulgaris and
A. verlotiorum. Additionally, achenes of A. campestris
and A. campestris ssp. sericea coming from different
localities and from different specimens show differences
in the process of swelling and slime formation. Fruits of
diploid (2n ¼ 2x ¼ 182Torrell et al., 2001) A. campestris, as well as of tetraploid (2n ¼ 4x ¼ 36 – Kreitschitz
and Vallès, 2003) individuals from two localities (Żagań
and Brzezia Ła˛ ka, Table 1), form a typical slime
envelope (Fig. 3H), similar to other taxa. Conversely,
achenes of tetraploid plants from four other localities
(but including also some specimens from Brzezia Ła˛ ka)
do not swell, although they clearly possess slime cells
(Fig. 1G). If swelling takes place, it only affects few cells
without visible slime envelope formation. A similar
result was obtained for the tetraploid A. campestris ssp.
sericea (2n ¼ 4x ¼ 36 – Kreitschitz and Vallès, 2003),
where fruits from two localities (Grzybowo and Ustka)
swelled (Fig. 4L), while those from another place
(Darłówko) did not.
Braune et al. (1975)
Gerlach (1972); Filutowicz and Kużdowicz
(1951)
Broda (1971); Filutowicz and Kużdowicz (1951)
Filutowicz and Kużdowicz (1951); Broda
(1971); Braune et al. (1975); Gerlach (1972)
Broda (1971); Johansen (1940); Filutowicz and
Kużdowicz (1951);
Braune et al. (1975); Gerlach (1972)
Discussion
As stated in the introduction, slime envelope formation
is known in several plant families, including the Asteraceae. Concerning Artemisia it has been reported to date in
A. arctica, A. subarctica, A. lagophus, A. lagocephala,
A. scoparia, A. armeniaca, A. palustris, A. taurica,
A. monosperma, A. absinthium and A. annua (Boyko,
1985; Grubert, 1974; Huang and Gutterman, 1999a, b;
Huang et al., 2000; Korobkov, 1973; Mouradian, 1995;
Oganesova, 1981; Yakovleva et al., 2002). Our results
confirm the presence of slime in the two latter species and
add six more taxa to the list of myxogenic Artemisia
(A. barrelieri, A. biennis, A. campestris, A. campestris
subsp. sericea, ;A. nova and A. pygmaea), these covering all
the five large subgenera in which the genus is traditionally
divided (Vallès and Garnatje, 2005 and references therein).
In addition, this is the first record of the presence of slime
in the genus Neopallasia. Previously, Young and Mayeux
(1996) studying the seed ecology of some Artemisia species
in subgenus Tridentatae did not report any species with
slime cells in the achenes, although they have referred to
mucilaginous trichomes in the seedlings. Our results reveal,
however, the presence of slime cells, and show slime
envelope formation in two members of this North
American endemic subgenus (A. nova and A. pygmaea),
in agreement with unpublished results on other taxa from
this group (S. Garcia, personal communication). We also
give the first report of the composition of the Artemisia
achene slime in a large set of taxa; earlier only Yakovleva
et al. (2002) mentioned the presence of cellulose as a
component of slime in some Artemisia taxa.
The structure of the slime cellulose threads is similar
in all the species studied, which is logical taking into
account their systematic closeness. The feature that
differs between taxa is the length of these threads.
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They are much longer in Neopallasia (3–4 times the
achene width) than in Artemisia (as long as the width of
the achene). The monotypic genus Neopallasia was
originally included in Artemisia and its taxonomic
position is still disputable. Differences in slime envelope
morphology may confirm the separate position of
this genus.
The ability to produce mucilaginous fruits, which is
typical of many Artemisia taxa growing in dry habitats,
was confirmed in our studies and is in agreement with
data by Korobkov (1973) and Huang et al. (2000).
Neopallasia grows in particularly dry habitats, where the
presence of slime in the achene may be an advantageous
adaptive feature facilitating germination. Additionally,
the increase of the nuclear DNA content is thought to be
an important adaptation to extreme environmental
conditions in Artemisia. This is usually the result of
polyploidization, but may also occur in diploids such as
A. pygmaea (Garcia et al., 2004).
The achenes of the taxa studied may differ in their
slime content. We hypothezise that such differences may
be associated with such factors as ploidy level, environmental conditions and life form. The achenes of some
polyploid taxa, even those possessing slime cells, may be
devoid of slime formation ability. This is the case of
some tetraploid specimens of A. campestris and
A. campestris ssp. sericea. In tetraploid plants of
A. campestris, the slime cells are normally present on
the achene surface but probably some fruits do not
mature, or produce only a scarce amount of slime that is
insufficient to form the envelope. Delayed maturation,
absence of fruits and developmental changes are
frequently the consequence of increased ploidy level
due to the change in the length of the cell cycle.
Polyploids often flower later than the diploids or
sometimes do not form flowers at all (Bayer, 1998;
Mizianty, 1994; Solbrig, 1977). For instance, tetraploid
plants of A. abrotanum rarely flower and are usually not
able to develop fruits (Kreitschitz, 2003). It is worth
noting that Mouradian (1995) included A. campestris
into the group devoid of slime cells. With the present
data, we confirm not only the presence of slime cells in
this species, but also the slime envelope formation in
several populations as well. Similarly, only a few
tetraploid specimens of A. campestris ssp. sericea ð2n ¼
4x ¼ 36Þ (Kreitschitz and Vallès, 2003) were able to
swell and to form a distinct slime envelope.
The number and distribution of slime strands on the
achene surface as well as their morphology may provide
us with additional information about the differences in
the slime amount in taxa studied. The slime layer
deposited in the slime cells makes them higher than the
proper epidermal cells. Pectin dessication may cause
shrinkage of the cell walls and, as a result, cell
obliteration, evident as ripples and folds on the achene
surface. Based on the fold structure in slime cell strands
in A. annua and A. barrelieri, it could be expected that
these species possess an enormous amount of slime. On
the other hand, delicate lines on the slime cell strands in
A. absinthium, A. dracunculus and A. biennis suggest
scarce slime production. Neopallasia pectinata is also
potentially rich in slime, as its achenes are covered by
numerous convex strands of slime cells. Consistently,
microstaining reactions do reveal a wide envelope
around the achenes of Neopallasia. Slime formation on
the fruit and/or seed surface is known to be an
ecological adaptation to limited availability of water
(Huang and Gutterman, 1999a; Huang et al., 2000;
Korobkov, 1973; Young and Martens, 1991). Differences in the slime amount can result from habitat
diversity. Such a relationship was reported in the
Lamiaceae (Mosquero et al., 2004). Apart from the
case of tetraploid specimens of A. campestris discussed
above, only in the cases of A. vulgaris and A. verlotiorum
does the slime envelope remain unformed, although the
slime cells are present on the achene surface in both
species. These two taxa occur in diverse habitats, mostly
growing in relatively fertile and wet environments such
as river and lake banks, field margins, gardens and
ruderal places (Cullen, 1975; Gams, 1987; Żukowski,
1971). It can be assumed that, in such environments,
slime presence may not be necessary to assure seed
germination. Therefore, the slime cells in these taxa may
not mature or function properly. Similar data were
given for Prunella (Lamiaceae), where the absence of
slime or its low production may result from not completely formed or not functional slime cells (Mosquero
et al., 2004).
On the other hand, in Artemisia dracunculus, growing
often on river banks (Gams, 1987; Rothmaler, 1987;
Żukowski, 1971), the presence of a slime envelope may
play an important role in the dispersal of this species.
The slime can reduce the specific weight of diaspores,
thus facilitating their transportation with the water
current (hydrochory) (Fahn and Werker, 1972; Huang
et al., 2000; Young and Evans, 1973).
Taxa, such as A. absinthium, A. campestris,
A. campestris ssp. sericea, A. pygmaea, A. barrelieri
and N. pectinata, occurring in less fertile and often arid
sandy locations (Cullen, 1975; Gams, 1987; Polyakov,
1995), are characterised by the presence of numerous
strands of slime cells. The slime cells cover the entire
achene surface and produce a distinct slime envelope in
these taxa. The slime envelope facilitates the adherence
of achenes to the soil surface, helps retain the water
around the fruit and makes germination easier
(Fahn and Werker, 1972; Huang et al., 2000; Young
and Martens, 1991). As Baiges et al. (1991) stated
for Euphorbia species, the slime in the dispersal units
(seeds or fruits) allows the plants, which produce it, to
create appropriate conditions for establishment and
germination.
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A. Kreitschitz, J. Vallès / Flora 202 (2007) 570–580
In some particular cases, production of slime on the
fruit and/or seed surface may also be an adaptation to
ruderal, disturbed environments (Young and Evans,
1973). The presence of a slime envelope is associated
with a short life cycle and facilitates a quick colonisation
of such places. We confirmed this kind of adaptation in
annual taxa like A. annua and A. biennis, growing in
disturbed areas, and N. pectinata, occurring in semideserts (Cullen, 1975; Polyakov, 1995; Żukowski, 1971).
Similar adaptive mechanisms are present in many
common annual weeds colonising ruderal habitats, e.g.
Lepidium flavum, L. nitidum, Plantago lanceolata,
Cardaria draba (Young and Evans, 1973) and Arabidopsis thaliana (Western et al., 2000).
Slime is an important factor regulating germination and
development of seedlings. It was reported that removal of
the slime envelope from seeds before germination may
affect seedling development and cause the decrease of
their size (Huang and Gutterman, 1999a, b; Huang et al.,
2000). The presence of the slime is also advantageous as
regards the protection of fruits and seeds from ingestion
by animals and from pathogen infection. It facilitates
dispersal (zoochory) and anchors seed to the soil surface
(Huang et al., 2000). It can be hypothesised, that for the
latter function a heterogenous type of slime, consisting of
two components, i.e. pectins and cellulose, is more
beneficial. Cellulose threads may strengthen the anchorage, thus keeping the achene in the soil. This is apparent
in the extremely long threads of N. pectinata, which can
protect the achene against wind dispersal.
Acknowledgements
The authors would like to thank: Prof. J. Da˛ browska
(Wrocław University), Dr. E.D. McArthur (USDA,
Provo, Utah), Dr. M. Klimczyńska-Szymura (Agricultural University Wrocław), Dr. K. Oklejewicz (Rzeszów
University), M. Torrell and Dr. A. Gómez (Universitat
de Barcelona) for their help in the collection of material,
Msc. A. Kamińska (Technical University of Wrocław)
and Msc. K. Heller (Agricultural University Wrocław)
for the SEM pictures preparation, Dr. T. Garnatje
(Institut Botànic de Barcelona), S. Garcia (Universitat
de Barcelona) for comments which improved the
manuscript, Dr. E. Gola and Dr. A. Banasiak (Wrocław
University) for their critical revision of this work and
S. Pyke (Jardı́ Botànic de Barcelona) for the correction
of the English language.
References
Baiges, J.C., Blanché, C., 1988. Morfologia de les granes de les
espècies ibèrico-balears del gènere Euphorbia L. (Euphorbiaceae), I. Subgen. Chamaesyce Rafin. Actes Simposi Int.
Bot. Pius Font i Quer II, 91–96.
579
Baiges, J.C., Espadaler, X., Blanché, C., 1991. Seed dispersal
in W Mediterranean Euphorbia species. Bot. Chron. 10,
697–705.
Bayer, J.L., 1998. New perspectives into the evolution of
polyploid complexes. In: Proceedings of the VIth International IOBP Symposium, Amsterdam, The Netherlands,
August 10–15, Hugo de Vries Laboratory, Amsterdam,
1999, pp. 359–373.
Boyko, E.V., 1985. On the systematics of Artemisia aurata and
Artemisia palustris (Asteraceae). Bot. Zhurn. 70, 923–925.
Braune, W., Leman, A., Taubert, H., 1975. Praktikum z
Anatomii Roślin. PWN, Warszawa.
Bremer, K., 1994. Asteraceae. Cladistic and Classification.
Timber Press, Portland, Oregon.
Broda, B., 1971. Metody Histochemii Roślinnej. PWZL,
Warszawa.
Cullen, J., 1975. Artemisia L. In: Flora of Turkey and the East
Aegean Islands, Vol. 5. University Press, Edinburg,
pp. 311–324.
Fahn, A., Werker, E., 1972. Anatomical mechanisms of seed
dispersal. In: Kozlowski, T.T. (Ed.), Seed Biology. Vol. I.
Importance, Development and Germination. Academic
Press, New York–London, pp. 151–221.
Filutowicz, A., Kużdowicz, A., 1951. Mikrotechnika roślinna.
PWR i L, Warszawa.
Frey-Wyssling, A., 1959. Die Pflanzliche Zellwand. Springer,
Berlin–Göttingen–Heidelberg.
Gams, H., 1987. Artemisia L. In: Hegi G. (Ed.), Illustrierte
Flora von Mittel-Europa, Spermatophyta, Band VI,
Angiospermae, Dicotyledones 4, Teil 4., Parey, BerlinHamburg, pp. 626–674.
Garcia, S., Sanz, M., Garnatje, T., Kreitschitz, A.,
McArthur, E.D., Vallès, J., 2004. Variation of DNA amount
in 47 populations of the subtribe Artemisiinae and related
taxa (Asteraceae, Anthemideae): Karyological, ecological,
and systematic implications. Genome 47, 1004–1014.
Gerlach, D., 1972. Zarys Mikrotechniki Botanicznej. PWRiL,
Warszawa.
Grubert, M., 1974. Studies on the distribution of myxospermy
among seeds and fruits of Angiospermae and its ecological
importance. Acta Biol. Venez. 8 (3–4), 315–551.
Huang, Z., Gutterman, Y., 1999a. Water absorption by
mucilaginous achenes of Artemisia monosperma: floating
and germination as affected by salt concentrations. Israel J.
Plant Sci. 47, 27–34.
Huang, Z., Gutterman, Y., 1999b. Germination of Artemisia
sphaerocephala (Asteraceae), occurring in the sandy desert
areas of Northwest China. S. Afr. J. Bot. 65, 187–196.
Huang, Z., Gutterman, Y., Hu, Z., 2000. Structure and
function of mucilaginous achenes of Artemisia monosperma
inhabiting the Negev desert of Israel. Israel J. Plant Sci. 48,
255–266.
Johansen, D.A., 1940. Plant microtechnique. McGraw-Hill
Book Company, INC, New York, London.
Johnson, L.A., Huish, K.H., Porter, J.M., 2004. Seed surface
sculpturing and its systematic significance in Gilia (Polemoniaceae) and segregated genera. Int. J. Plant Sci. 165, 153–172.
Kreitschitz, A., 2003. Zróżnicowanie morfologiczne i cytologiczne wybranych gatunków rodzaju Artemisia L. z Dolnego
Śla˛ ska. Ph.D. Dissertation, University of Wrocław.
ARTICLE IN PRESS
580
A. Kreitschitz, J. Vallès / Flora 202 (2007) 570–580
Kreitschitz, A., Vallès, J., 2003. New or rare data on
chromosome numbers in several taxa of the genus Artemisia
L. (Asteraceae) in Poland. Folia Geobot. 38, 333–343.
Korobkov, A.A., 1973. Morpho-anatomical peculiarities of
achene of Artemisia ssp. from north-east of the USSR. Bot.
Zhurn. 58, 1302–1315.
Mizianty, M., 1994. Natura poliploidów. Wiad. Bot. 38 (1/2),
57–66.
Mosquero, M.A., Juan, R., Pastor, J., 2004. Observaciones
micromorfológicas y anatómicas en núculas de Prunella L.
y Cleonia L. (Lamiaceae) del suroeste de España. Acta Bot.
Malac. 29, 203–214.
Mouradian, L.G., 1995. Comparative morpho-anatomical
investigation of the achenes of Filifolium Kitam. and
related genera. In: Hind, D.J.N., Jeffrey, C., Pope, G.V.
(Eds.), Advances in Compositae, Systematics. Royal
Botanic Gardens, Kew, pp. 41–49.
Mühlethaler, K., 1950. The structure of plant slimes. Exp. Cell
Res. 1, 341–350.
Oganesova, G.G., 1981. Anatomical structure of four species
of Artemisia from seria Maritimae (Asteraceae). Bot. Zhur.
66, 1293–1130.
Ouyahya, A., Viano, J., 1984. Contribution à l’étude morphologique et biométrique des akènes de taxons endémiques
marocains du genre Artemisia. Lagascalia 12, 223–228.
Ouyahya, A., Viano, J., 1990. Étude au MEB du test des
akènes du genre Artemisia. Bol. Soc. Brot., Sér. 2 63,
99–113.
Plaza, L., Fernández, I., Juan, R., Pastor, J., Pujadas, A.,
2004. Micromorphological studies on seeds of Orobanche
species from the Iberian Peninsula and the Balearic Islands,
and their systematic significance. Ann. Bot. 94, 167–178.
Polyakov, P.P., 1995. Artemisia L. In: Flora of the USSR, Vol.
XXVI. Bischen Singh Mahendra Pal Singh and Koeltz
Scientific Books, pp. 488–723.
Rothmaler, W., 1987. Exkursionsflora. Gefäßpflanzen. Band
2. Volk und Wissen, Berlin.
Solbrig, T.O., 1977. Chromosomal cytology and evolution in
the family Compositae. In: Heywood, V.H., Hardborne, B.J.,
Turner, B.L. (Eds.), The Biology and Chemistry of
Compositae. Academic Press, London – New York – San
Francisco, pp. 267–279.
Torrell, M., Vallès, J., 2001. Genome size in 21 Artemisia L.
species (Asteraceae, Anthemidiae): Systematic, evolutionary, and ecological implications. Genome 44, 231–238.
Torrell, M., Cerbah, M., Siljak-Yakovlev, S., Vallès, J., 2001.
Étude cytogènètique de trois taxons du complexe d’Artemisia campestris L. (Asteraceae, Anthemideae): localisation
de l’hétérochromatine et de l’ADN ribosomique. Bocconea
13, 623–628.
Vallès, J., Garnatje, T., 2005. Artemisia and its allies: genome
organization and evolution and their biosystematic, taxonomic and phylogenetic implications in the Artemisiinae
and related subtribes (Asteraceae, Anthemideae). In:
Sharma, A. (Ed.), Plant Genome: Biodiversity and Evolution. Vol. 1B: Phanerogams. Enfield, M/S Science Publishers, pp. 255–285.
Vallès, J., McArthur, E.D., 2001. Artemisia systematics and
phylogeny: cytogenetic and molecular insights. USDA
Forest Service Proceedings RMRS-P-2, pp. 67–74.
Vallès, J., Seoane, J.A., 1992. Estudis carpològics en el gènere
Artemisia a la Penı́nsula Ibèrica i les Illes Balears. Actes del
Simposi Internacional de Botànica Pius Font i Quer, Vol. 1,
Fanerogàmia, Lleida, Institut d’Estudis Ilerdencs, pp.
211–215.
Western, T.L., Debra, J.S., Haughn, G.W., 2000. Differentation of mucilage secretory cells of the Arabidopsis seed coat.
Plant Physiol. 122, 345–355.
Wojciechowska, B., 1961. Morfologiczne i anatomiczne cechy
owoców środkowoeuropejskich gatunków rodzaju Prunella
L. z rodziny Lamiaceae. Monogr. Bot. 12, 49–88.
Wojciechowska, B., 1966. Morfologia i anatomia owoców i
nasion z rodziny Labiatae ze szczególnym uwzgl˛ednieniem
gatunków leczniczych. Monogr. Bot. 21, 3–243.
Yakovleva, O.V., Korobkov, A.A., Boyko, E.V., 2002.
Structure of mucilage containing cells in achene pericarp
of some species of Artemisia (Asteraceae). Bot. Zhur. 87 (9),
1–14.
Young, J.A., Evans, R.A., 1973. Mucilaginous seed coats.
Weed Sci. 21, 2–54.
Young, J.A., Martens, E., 1991. Importance of hypocotyl hairs
in germination of Artemisia seeds. J. Range Manage. 44,
438–442.
Young, J.A., Mayeux, H., 1996. Seed ecology of woody species
of Artemisia and Chrysothamnus. In: Caligari, P.D.S.,
Hind, D.J.N. (Eds.), Compositae: Biology and Utilization.
In: Proceedings of International Compositae Conference,
Kew, 1994, Vol. 2, Roy. Bot. Gard., Kew, pp. 93–104.
Zeng, C., Wang, J., Liu, A., Wu, X., 2004. Seed coat
microsculpturing changes during seed development in
diploid and amphiploid Brassica species. Ann. Bot. 93,
555–566.
Żukowski, W., 1971. Artemisia L. In: Pawłowski, B., Jasiewicz, A.
(Eds.), Flora Polska, Rośliny Naczyniowe Polski i
Ziem Ościennych, Tom XII, Warszawa-Kraków, PWN,
pp. 288–304.