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Anatomy and Development of Leaves in Chamaecrista mimosoides and C. nomame (Leguminosae-Caesalpinioideae)

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Chamaecrista mimosoides (L.) Greene has a unique even-pinnate leaf with crenate-crested protuberances on the adaxial side of the rachis between leaflet pairs, which is one of the important characteristics for distinguishing it from other species with leaf rachises canaliculate. The present study clarified anatomical and developmental features of the leaves with the crenate-crested rachis in C. mimosoides in comparison with those with a canaliculate rachis in C. nomame (Makino) H. Ohashi. Transverse sections showed that the crenate-crested rachis has a protuberance constructed by continuous parenchymatous tissues composed of cells rich in chloroplasts, whereas the canaliculate one has two ridges constructed by two independent parenchymatous tissues. Developmental observations showed that the crenate-crested rachis is initiated as a single swelling of tissues, whereas the canaliculate one initiated as two parallel swelling of tissues. Both rachises have commonly two ridge bundles divided from the main vascular bundles in the petiole, but the two ridge bundles are fused into one bundle in the proximal half of the crenate-crested protuberance between leaflet pairs, and then divided into two again in the distal half. In contrast, the two ridge bundles remain separated throughout the length in the canaliculate rachis. The fused ridge bundles in the crenate-crested protuberance, moreover, branch a small bundle into the protuberance. At the distal part of the petiole there is an extrafloral nectary (EFN) in both species. The vascular bundles are supplied to the EFN from each of two ridge bundles in the petiole in C. mimosoides, whereas from the main vascular bundles in C. nomame. The repetition of fusion and separation of two ridge bundles in the crenate-crested leaf rachis seems to support the idea that the rachis is produced by fusion of two ridges of the canaliculate rachis. The chloroplast-rich cells observed in the crenate-crested protuberance as well as many stomata in the epidermis suggest that the protuberance may improve the ability of photosynthesis.
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Anatomy and Development of Leaves in Chamaecrista mimosoides
and C. nomame (Leguminosae-Caesalpinioideae)
Tomoyuki NemOtOa,*, Hiroyoshi Ohashib and Te-Lin Wuc
aDepartment of Biological Sciences, Faculty of Science and Engineering, Ishinomaki Senshu University,
1 Shinmito, Minamisakai, Ishinomaki, 986-8580 JAPAN;
bBotanical Garden, Tohoku University, Sendai, 980-0862 JAPAN;
cHerbarium, South China Institute of Botany, Chinese Academy of Sciences,
Wushan, Guangzhou, Guangdong 510650, P. R. CHINA
*Corresponding author: tnemoto@isenshu-u.ac.jp
(Accepted on August 31, 2016)
Chamaecrista mimosoides (L.) Greene has a unique even-pinnate leaf with crenate-crested
protuberances on the adaxial side of the rachis between leaet pairs, which is one of the important
characteristics for distinguishing it from other species with leaf rachises canaliculate. The present
study claried anatomical and developmental features of the leaves with the crenate-crested rachis
in C. mimosoides in comparison with those with a canaliculate rachis in C. nomame (Makino)
H. Ohashi. Transverse sections showed that the crenate-crested rachis has a protuberance
constructed by continuous parenchymatous tissues composed of cells rich in chloroplasts,
whereas the canaliculate one has two ridges constructed by two independent parenchymatous
tissues. Developmental observations showed that the crenate-crested rachis is initiated as a single
swelling of tissues, whereas the canaliculate one initiated as two parallel swelling of tissues. Both
rachises have commonly two ridge bundles divided from the main vascular bundles in the petiole,
but the two ridge bundles are fused into one bundle in the proximal half of the crenate-crested
protuberance between leaet pairs, and then divided into two again in the distal half. In contrast,
the two ridge bundles remain separated throughout the length in the canaliculate rachis. The
fused ridge bundles in the crenate-crested protuberance, moreover, branch a small bundle into the
protuberance. At the distal part of the petiole there is an extraoral nectary (EFN) in both species.
The vascular bundles are supplied to the EFN from each of two ridge bundles in the petiole in C.
mimosoides, whereas from the main vascular bundles in C. nomame. The repetition of fusion and
separation of two ridge bundles in the crenate-crested leaf rachis seems to support the idea that
the rachis is produced by fusion of two ridges of the canaliculate rachis. The chloroplast-rich cells
observed in the crenate-crested protuberance as well as many stomata in the epidermis suggest
that the protuberance may improve the ability of photosynthesis.
Key words: Anatomy, Caesalpinioideae, Cassieae, Chamaecrista mimosoides,
Chamaecrista nomame, development, extra oral nectary, Leguminosae, leaf, leaf rachis.
J. Jpn. Bot. 91 Suppl.: 201–216 (2016)
The genus Chamaecrista Moench is a
pantropical and subtropical genus of about 330
species, with greatest diversity in Central and
South America and tropical Africa (Lewis 2005).
Species of this genus were formerly placed as
parts of the genus Cassia L. (Candolle 1825,
202 The Journal of Japanese Botany Vol. 91 Centennial Memorial Issue
Bentham 1865, 1871, Baker 1878, De Wit 1955,
Ohwi 1953, 1965, Ohashi 1982, Chen 1988),
but the genus Cassia is commonly recognized
as segregated into three genera, Cassia sensu
stricto, Senna and Chamaecrista according to
Irwin and Barneby (1981, 1982) in recent oras
(e.g., Pedley 1998, Chen et al. 2010, Ohashi
2016). Chamaecrista is divided into six sections
(Irwin and Barneby 1981, 1982). In Asia, 16
species have been recognized in total (Lock and
Simpson 1991, Kumar and Sane 2003, Lock
and Heald 1994, Lock and Ford 2004, Zhu et al.
2007, Choi 2007, Ohashi 1999), and almost all
Asian species except C. absus (sect. Absus) are
attributed to sect. Chamaecrista according to
Irwin and Barneby’s key (1982).
Among these Asian species, Chamaecrista
mimosoides (L.) Greene is the most widely
distributed species, extending into Africa (Lock
1989) and Australia (Pedley 1998). The leaf
rachis of C. mimosoides was described as “of the
young leaves furnished on its upper side with a
crenated margin” by Wight and Walker-Arnott
(1834, as Cassia angustissima Lam.). The leaf
rachis, distinctly crenated or crenate-crested on
the adaxial side between leaet pairs, has been
regarded as unique to C. mimosoides (or Cassia
mimosoides) and adopted as a useful character
distinguishing it from other species with distinct
leaf rachis grooved, canaliculate or channeled
along the adaxial side in oras of various regions
(Ghesquière 1932, Steyaert 1950, Brenan 1967,
Larsen et al. 1980, Rudd 1991, Larsen and Ding
1996, Pedley 1998, Singh 2001, Du Puy 2002).
Brenan (1967) noted the leaf rachis as one of
the most significant features for separating the
species under the genus Cassia sensu lato in the
tropical East Africa and that there is a channel
running along the upper side of the leaf rachis
in most species, while some species including
Cassia mimosoides have a raised wing-like
projection running along the upper side of the
rachis. Du Puy (2002) also listed the presence
or absence of a crenate crest along the upper
side of the leaf rachis as one of the most useful
characters in distinguishing between the species
in Madagascar.
Lock (2007) considered that the solid crest of
the crenate-crested rachis is produced by fusion
of two ridges of the canaliculate rachis. Leaf
structure including rachises has been examined in
Chamaecrista (or as Cassia) by several authors
such as Watari (1934, as Cassia mimosoides
var. nomame), Saheed and Illoh (2010,
Cassiinae including Chamaecrista mimosoides),
Coutinho et al. (2013, Chamaecrista sect. Absus
subsect. Baseophyllum), Francino et al. (2015,
Chamaecrista sect. Absus). But Chamaecrista
mimosoidessect. Chamaecristaitself and the
unique crenate-crested leaf rachis have not been
examined so far. Although the unique rachis
feature has been recognized, our understandings
of the structural relationships between the
crenate-crested leaf rachises and canaliculate
ones have been poor.
The present study aims to clarify the
structural relationships between the crenate-
crested rachises and the canaliculate ones in
Chamaecrista. For this objective we performed
anatomical and developmental analyses on the
crenate-crested rachises of C. mimosoides in
comparison with the canaliculate ones of C.
nomame (Makino) H. Ohashi.
Materials and Methods
Morphology and structure of leaf
rachises were examined anatomically and
organogenetically in Chamaecrista mimosoides
(L.) Greene and C. nomame (Makino) H.
Ohashi. Materials of C. mimosoides were
collected from Hushan hill, Jianfeng, Ledong
Co, Hainan, China on 21 Oct. in 1993 (Voucher:
T. Nemoto et al. 1021001) and those of C.
nomame collected from Narusegawa River,
Junai, Nakaniida-machi, Kami-gun, Miyagi
Prefecture, Japan on 18 Aug. in 1983 (Voucher:
T. Nemoto 2277). Collected materials were
preserved in FAA. Both voucher specimens are
kept in TUS.
Leaves were examined according to the
December 2016 Nemoto et al.: Anatomy and development of leaves in Chamaecrista 203
developmental stages along some shoots from
proximal to distal orders. Within a leaf the distal
half was used for SEM observations and the
remaining proximal half used for anatomical
ones. For morphological observations using
SEM, leaves were dissected and half of the
leaets were removed for enabling observation
of the rachis above between leaflet pairs, then
dehydrated through an ethyl alcohol series,
transferred to t-butyl alcohol, freeze-dried in a
Freeze Dryer VFD-21S, mounted on brass stubs,
coated with gold, and observed by a JEOL JSM-
6380LV scanning electron microscope. For
anatomical observations, leaves were dehydrated
through an ethanol series and embedded in a
methacrylate resin (Technovit 7100). Sections
were made using a Leica RM2165 rotary
microtome at a thickness of 2 or 3 µm, stained
with 0.05% Toluidine Blue O in benzoate
buffer, pH 4.4 (Feder and O’Brien 1968) and
then mounted with Entellan. Observations were
performed with a Leica DMRX light microscope
and photographs were taken with a Leica DC
200 digital camera.
Results
Morphology and anatomy of the leaf rachis
Leaves are even-pinnate both in
Chamaecrista mimosoides and C. nomame.
The leaf is composed of pulvinus, petiole and
rachis with many regions of leaet pair insertion.
Mature leaves of C. mimosoides have crenate-
Fig. 1. Morphology of leaf rachis in Chamaecrista mimosoides (A, C, E) and C. nomame (B, D, F). A. Crenate-
crested leaf rachis, showing crenate protuberances (arrows) on the adaxial side of the rachis between leaet pairs.
B. Canaliculated leaf rachis, showing two ridges (arrows) on the adaxial side of the rachis between leaet pairs.
C. Transverse section of the crenate-crested leaf rachis between leaet pairs, showing a protuberance (arrow). D.
Transverse section of the canaliculated leaf rachis between leaet pairs, showing two ridges (arrows) and groove
formed between these ridges. E. Transverse section of the crenate-crested leaf rachis between leaet pairs, showing
two but joined ridge bundle (arrowhead) supplied to a protuberance. F. Transverse section of the canaliculated leaf
rachis between leaet pairs, showing two ridge bundles (arrowheads) supplied to two ridges. lt, leaet; mb, main
vascular bundles of rachis; ٭, scar of leaet removed. Scale bars: 200 μm (A, B); 50 μm (C, E); 100 μm (D, F).
204 The Journal of Japanese Botany Vol. 91 Centennial Memorial Issue
crested ridges between leaflet pairs on the
adaxial side of their rachises and the ridges are
ca. 200 μm height from the upper margin of the
leaet base (Fig. 1A). The surface of the ridges
is almost glabrous. Mature leaves of C. nomame
have rachises grooved or canaliculate on their
adaxial side between leaet pairs (Fig. 1B). Two
ridges forming the groove are covered with
trichomes.
Transverse sections of leaf rachises showed
that the crenate-crested ridge of Chamaecrista
mimosoides is composed of just a single
swelling of tissues (Fig. 1C, E), whereas the
canaliculate rachis of C. nomame is composed
of two swellings of tissues forming the groove
(Fig. 1D, F). The vascular tissues form a
cylinder surrounded by sclerenchyma cells or
bers. There is one additional vascular bundle in
C. mimosoides and two bundles in C. nomame.
The number of these vascular bundles is in
accordance with the number of ridges between
leaflet pairs, and they are those called ridge
bundles (Watari 1934), rib traces (Howard
1979) or accessory bundles (Coutinho et al.
2013, Francino et al. 2015). These bundles are
also abaxially or externally associated with
sclerenchyma cells. In C. mimosoides, moreover,
a small seemingly vascular tissue is found in the
crenate-crested swelling (Fig. 5, arrowhead).
Chloroplasts contained in the parenchyma cells
between the epidermis and the vascular tissues
are more conspicuous in C. mimosoides than C.
nomame (Fig. 1E, F).
Development of leaf rachis between leaet pairs
Chamaecrista mimosoides In the leaf of
ca. 1.8 mm long (Fig. 2A, B), leaflet pairs are
borne close to each other and club-shaped or
short bottle-shaped colleters are borne on the
adaxial side of the rachis. Each colleter is located
just between leaet pairs. The adaxial surface of
the rachis between colleters is ca. 20 μm long
and flat, on which there are no protuberances
observed. The main vascular bundles of the
rachis have begun differentiating. Although
unicellular trichomes are already borne on the
abaxial side of the rachis, they are not on the
adaxial side.
In the leaf of ca. 3 mm long (Fig. 2C, D),
the length of the rachis between leaflet pairs
is ca. 94 μm. A protuberance is observed on
the adaxial side of the rachis between leaflet
pairs. The height of the protuberance from the
upper margin of the leaflet base is ca. 25 μm.
Unicellular trichomes have been borne between
the protuberances on the adaxial side of the
rachis.
In the leaf of ca. 6.5 mm long (Fig. 2E, F),
the length of the rachis between leaflet pairs is
ca. 135 μm. The protuberances between leaflet
pairs become conspicuous, more than 50 μm in
height and crenate in form. Although there are
few colleters and trichomes between the crenate
protuberances, the protuberance itself is still
glabrous.
In the leaet of almost mature leaf of ca. 28
mm long (Fig. 2G), the protuberance becomes
more than 400 μm long in length and more
than 130 μm in height. The surface is almost
glabrous, but many stomata are observed
differentiating on it (Fig. 2H).
Chamaecrista nomame In the leaf of
ca. 3.4 mm long (Fig. 3A, B), leaflet pairs are
borne close to each other and short bottle-shaped
colleters are borne on the adaxial side of the
rachis. Each colleter is located just between
leaflet pairs. The adaxial surface of the rachis
between colleters is ca. 40 μm long and at, on
which there are no protuberances observed. The
main vascular bundles of the rachis have begun
differentiating. Although unicellular trichomes
are already borne on the abaxial side of rachis,
they are not on the adaxial side.
In the leaf of ca. 4.2 mm long (Fig. 3C, D),
the length of the rachis between leaflet pairs
is ca. 80 μm. Two protuberances are borne in
parallel on the adaxial side of the rachis between
leaflet pairs or between colleters at this stage.
The height of the protuberances from the upper
margin of the leaflet base is less than 25μm.
December 2016 Nemoto et al.: Anatomy and development of leaves in Chamaecrista 205
Fig. 2. Leaf rachis development in Chamaecrista mimosoides. A. Leaf of ca. 1.8 mm long, showing the adaxial side of
rachis with no protuberances initiated (arrows) between leaet paris. B. Transverse section of A at the rachis between
leaet pairs, showing the adaxial surface of rachis still being at (arrow). C. Leaf of ca. 3 mm long, showing initiation
of protuberances (arrows) along the adaxial side of rachis between leaet pairs. D. Transverse section of C at the rachis
between leaet pairs, showing a protuberance (arrow). E. Leaf of ca. 6.5 mm long, showing protuberances (arrows)
growing along the adaxial side of rachis between leaet pairs. F. Transverse section of E at the rachis between leaet
pairs, showing a protuberance (arrow). G. Almost mature leaf of ca. 28 mm long, showing a protuberance (arrow) along
the adaxial side of rachis between leaet pairs. H. The protuberance of G enlarged, showing stomata (arrowheads) on the
surface. c, colleter; lt, leaet; mb, main vascular bundles of rachis; ٭, scar of leaet removed. Scale bars: 20 μm (A, B);
50 μm (C–F); 100 μm (G, H).
206 The Journal of Japanese Botany Vol. 91 Centennial Memorial Issue
Fig. 3. Leaf rachis development in Chamaecrista nomame. A. Leaf of ca. 3.4 mm long, showing the adaxial side of rachis
with no protuberances initiated (arrows) between leaet pairs. B. Transverse section of A at the rachis between leaet
pairs, showing the adaxial surface of rachis still being flat (arrow). C. Leaf of ca. 4.2 mm long, showing initiation
of protuberances (arrows) along the adaxial side of rachis between leaflet pairs. D. Transverse section of C at the
rachis between leaet pairs, showing two protuberances (arrows). E. Leaf of ca. 6 mm long, showing protuberances
(arrows) growing and covered by trichomes. F. Transverse section of E at the rachis between leaet pairs, showing two
protuberances growing and forming two ridges (arrows). c, colleter; lt, leaet; mb, main vascular bundles of rachis; ٭,
scar of leaet removed. Scale bars: 20 μm (A, B); 50 μm (C–F).
There are no unicellular trichomes borne on the
surface of the protuberances.
In the leaf of ca. 6 mm long (Fig. 3E, F), the
length of the rachis between leaflet pairs is ca.
125 μm. The number of colleters between leaet
pairs increases to two and unicellular trichomes
are borne on and between the protuberances.
Two protuberances form a groove of ca. 40 μm
in depth between them on the adaxial side of the
rachis.
Anatomical features from node to petiole
The leaf is supplied with three foliar traces,
or trilacunar type, in both species (Fig. 4A, E).
After the two lateral traces divide into stipule
traces, the three traces fuse with each other and
December 2016 Nemoto et al.: Anatomy and development of leaves in Chamaecrista 207
Fig. 4. Vascular system from the node of stem to petiole (A–H) and extrafloral nectary (EFN) (I–L) in Chamaecrista
mimosoides and C. nomame. A–D, I and J. C. mimosoides. E–H, K and L. C. nomame. A, E. Node of stem, showing the
departure of three foliar traces (arrows) from the vascular cylinder of stem. B, F. Middle part of pulvinus, showing the
main bundles formed in arc by three leaf traces fused. C, G. Near distal end of pulvinus, showing a pair of ridge bundles
(arrows) separated from the both margins of the arc of petiolar bundle. D, H. Slender part of petiole between pulvinus and
extraoral nectary, showing slight two ridges (D) vs. obvious ones (H), a pair of ridge bundles (arrows) running beneath
the two ridges (D, H), main vascular bundles in arc (D) vs. those divided into three (H), and bers externally collateral
with vascular bundles (D, H). I, K. EFN borne on the distal end of petiole, showing the position of EFN closer to the rst
leaet pair in I than in K and the differences in size and shape. J, L. Transverse section of petiole at EFN, showing traces
(arrowhead) supplied to EFN from ridge bundle in J and from both margins of the arc of main vascular bundles in L. lt,
rst leaet; mb, main vascular bundles of rachis; n, EFN; p, crenate-crested protuberance; ٭, scar of rst leaet removed.
Scale bars: 100 μm.
208 The Journal of Japanese Botany Vol. 91 Centennial Memorial Issue
December 2016 Nemoto et al.: Anatomy and development of leaves in Chamaecrista 209
form a central arc in the pulvinus (Fig. 4B, F).
At the distal part of the pulvinus two vascular
bundles, or ridge bundles, are separated from
the central arc toward the adaxial side (Fig. 4C,
G). The adaxial ridges of the petiole are slight in
Chamaecrista mimosoides (Fig. 4D), whereas
they are obvious in C. nomame, but a pair of
ridge bundles obviously runs along the ridges
in both species (Fig. 4D, H). The central arc
running in the pulvinus is still as an arc in the
petiole in C. mimosoides, whereas it divides into
three bundles in C. nomame. These three bundles
of C. nomame become an arc connecting to each
other in the distal part of the petiole (Fig. 4L).
At the distal end of the petiole, immediately
below the rst leaet pair, there is one extraoral
nectary (EFN) in both species (Fig. 4I, K).
The EFN appears slightly sunken in a shallow
hollow surrounded by the ridges on the adaxial
side of the petiole. The EFN of C. mimosoides
is flat and dish-shaped, while those of C.
nomame is larger, rounded and thicker than C.
mimosoides. The EFN tissues are composed of
a layer of epidermis and parenchyma below the
layer. The parenchyma appears to be composed
of two areas: the distal area composed of cells
with dark-stained cytoplasm, and the proximal
area composed of cells without such stained
cytoplasm. The vascular tissues are supplied to
the EFNs from each of two ridge bundles in C.
mimosoides (Fig. 4J), whereas they are supplied
from both margins of the central vascular arc
in C. nomame (Fig. 4L). The vascular tissues
enter within the proximal area, and they appear
to be composed mainly of phloem cells. The
epidermis of the EFN is slightly elevated at the
central area of the top in both species (Fig. 4J,
L).
Vascular system in leaf rachis through the region
of leaet pair insertion
Chamaecrista mimosoides The main
vascular bundles are arranged in a circle or
cylinder surrounded by a complete ring of
fibers throughout the rachis (Fig. 5A–L).
The ridge bundles running along the crenate-
crested protuberance form a single bundle at the
proximal half of the region between leaet pairs
(Fig. 5A, B, I–L). Around the middle part of the
region between leaflet pairs, the height of the
crenate-crested protuberance becomes the tallest
and the ridge bundle is divided into two bundles
(Fig. 5C). These two ridge bundles run toward
the next region of leaet pair insertion (Fig. 5D
F). Near the region of leaflet pair insertion the
leaet trace begins to depart from both sides of
the main vascular cylinder of the rachis (Fig.
5F). Each of two ridge bundles branches off a
bundle laterally and outward, which connects
with each leaflet trace on both sides of the
region of leaet pair insertion (Fig. 5G, H), then
two ridge bundles fuse to each other forming
a single ridge bundle when the crenate-crested
protuberance becomes increasing the height,
Fig. 5. Vascular system in leaf rachis through the region of leaflet pair insertion in Chamaecrista mimosoides. Serial
transverse sections are arranged from proximal to distal parts across the region. A–C. Leaf rachis between leaets pairs
and proximal half, increasing the height of crenate-crested protuberance toward the tallest middle part, showing single
ridge bundle (arrow in A, B), an additional small bundle (arrowhead in A–C) and division of the single ridge bundle into
two (arrows in C) around the middle part. D–F. Leaf rachis between leaet pairs and distal half, decreasing the height of
crenate-crested protuberance toward the region of leaet pair insertion, showing two ridge bundles remaining separated
to each other (arrows), leaet bundles starting departure from the ring of main vascular bundles (F), and additional small
bundle becoming invisible across these region (E, F). G–I. Leaf rachis at the region of leaet pair insertion, showing
the connection between ridge bundle and leaet bundle when the height of ridge almost lost (G), and two ridge bundles
fusing into a single bundle again as the height of crenate-crested protuberance increasing (H, I). J–L. Leaf rachis above
the region of leaet pair insertion, showing the increasing height of crenate-crested protuberance, single ridge bundle
(arrow), and an additional small bundle (arrowhead) divided from the ridge bundle into the protuberance. lb, leaflet
bundle; lt, leaet; mb, main vascular bundles of rachis. Scale bar: 100 μm.
210 The Journal of Japanese Botany Vol. 91 Centennial Memorial Issue
Fig. 6. Vascular system in leaf rachis through the region of leaet pair insertion in Chamaecrista nomame. Serial transverse
sections are arranged from proximal to distal parts across the region. A. Leaf rachis below the region of leaet insertion,
showing two ridge bundles (arrows) running along two ridges and leaet bundles starting departure from the ring of
main vascular bundles. B–G. Leaf rachis at the region of leaet pair insertion, showing the division of each ridge bundle
into two external and internal ones (B), the external bundles connecting with leaet bundles on both sides (C, D), the
internal bundles becoming next two ridge bundles (arrows) (D–F), and small bundle (arrowhead) apparently connecting
these two ridge bundles (C–E). H, I. Leaf rachis above the region of leaet pair insertion, showing the increasing height
of ridge, the increasing depth of groove between two ridges, and two ridge bundles running under two ridges. lb, leaet
bundle; lt, leaet; mb, main vascular bundles of rachis. Scale bar: 100 μm.
December 2016 Nemoto et al.: Anatomy and development of leaves in Chamaecrista 211
even before separating leaflets at the region
(Fig. 5I). The ridge bundle continues fusing
until the middle of the region between leaflet
pairs (Fig. 5J–L), and then again divides into
two bundles (Fig. 5A–C). Within the crenate-
crested protuberance an additional small bundle
is also observed departing from the fused single
ridge bundle at the proximal part of the region
between leaflet pairs (Fig. 5K, L). The small
bundle runs until the middle part of the region
between leaet pairs and simultaneously moves
toward the distal part, or the adaxial part, of the
protuberance (Fig. 5A–D), and then the bundle
can’t be conrmed (Fig. 5E).
Chamaecrista nomame ―The main
vascular bundles are arranged in a circle or
cylinder surrounded by a complete ring of bers
throughout the rachis (Fig. 6A–I). The two ridge
bundles run along the adaxial two ridges of the
region between leaflet pairs toward the next
region of leaet pair insertion (Fig. 6A, I). Two
leaflet traces begin departing from the main
vascular cylinder before the region of leaet pair
insertion (Fig. 6A). At the region of leaet pair
insertion each of two ridge bundles branches off
a bundle laterally and outward, which connects
with each leaet trace on both sides of the region
(Fig. 6B–D). The two ridge bundles appear
connected to each other by another bundle
branched laterally (Fig. 6C–E, arrowheads).
Although the adaxial two protuberances forming
the ridges are absent throughout this region, two
ridge bundles remain separating (Fig. 6B–G).
After two leaets are separated from both sides
of the rachis at the region, two ridges become
obvious (Fig. 6H, I).
Discussion
Comparison in external and internal
morphology between two leaf rachis types
The crenate-crested leaf rachis of
Chamaecrista mimosoides and the canaliculate
one of C. nomame are obviously different in
their external features: the former is made up
of one protuberance of tissues between leaflet
pairs, whereas the latter is made up of two
protuberances of tissues forming two ridges
parallel to each other between leaflet pairs.
The vascular system within the rachis has the
following similarities in both: (1) there are a
vascular ring or cylinder, called siphonostele, at
the center, and (2) there are basically a pair of
ridge bundles that are detached from the adaxial
margins of the vascular arc near the distal end
of the pulvinus and run along the adaxial side of
the petiole and the rachis of the leaf. However,
a pair of ridge bundles fuses into one at the
proximal half of the region between leaflet
pairs in the crenate-crested rachis and they are
separated into two again in the distal half of the
region and in the region of leaet pair insertion
in C. mimosoides. Moreover, an additional small
vascular bundle is observed in the proximal half
of the crenate-crested protuberance, which is
departed from the fused ridge bundle and runs
upward and in the center of the protuberance. In
contrast, a pair of ridge bundles is never fused
into one throughout the canaliculate rachis and
there are no additional bundles supplied in the
two ridges in C. nomame.
Vascular system from node to petiole
Leaves of Chamaecrista mimosoides and
C. nomame are both supplied with three foliar
traces, the nodal structure of which is that called
the trilacunar type (Sinnott 1914) and this type
of nodal structure has been known as common in
Leguminosae (Sinnott 1914, Sinnott and Bailey
1914, Watari 1934). The vascular bundles of the
pulvinus form the central vascular arc and divide
two ridge bundles from the adaxial margins of
the arc at the distal part of the pulvinus in both
species. A pair of ridge bundles in the petiole
is commonly observed in Cassia, Senna and
Chamaecrista (Watari 1934, as Cassia sensu
lato).
After dividing two ridge bundles in the
pulvinus, the main vascular bundles present
an arc shape in the petiole in C. mimosoides,
whereas they are divided into three bundles in
212 The Journal of Japanese Botany Vol. 91 Centennial Memorial Issue
C. nomame. Variation of vascular bundles in the
petiole was shown by Watari (1934) in Cassia
sensu lato, and the feature of his sole material
of Chamaecrista, C. nomame (as Cassia
mimosoides var. nomame), is consistent with
the present result. In Chamaecrista sect. Absus,
variations in the number of ridge bundles (as
accessory bundles), two or four to six, and in
disposition of the vascular bundles within the
petiole were reported (Coutinho et al. 2013).
Phylogenetic signicance of such variations has
not yet confirmed critically in Chamaecrista
sect. Absus. With respect to sect. Chamaecrista,
anatomical data of leaf rachises have not
yet accumulated enough for confirming its
phylogenetic signicance.
Vascular system related with extraoral nectary
The presence of an extrafloral nectary
(EFN) is one of important characteristics for
distinguishing Chamaecrista from Senna
and Cassia: the EFN is present in some of
Chamaecrista and Senna, but absent in Cassia;
the EFN of Chamaecrista is dish- or cup-
shaped, rarely at, while that of Senna is ovoid,
globose, mounded, claviform or phalloid (Irwin
and Barneby 1982). In Chamaecrista the EFNs
are known from four sections (Apoucouita,
Caliciopsis, Chamaecrista and Xerocalyx) and
a part of sect. Absus (Irwin and Barneby 1982,
Coutinho et al. 2012, Coutinho and Meira 2015),
and the EFNs are present on the petiole/rachis,
therefore also called “petiolar glands” (Irwin
and Barneby 1982). The molecular phylogenetic
analyses supported the presence of EFNs as
synapomorphic in Chamaecrista (Conceição et
al. 2009).
Chamaecrista mimosoides and C. nomame
have similar EFNs on the petiole immediately
below the first leaflet pair, but the EFNs are
different in the vascular tissues supplied as well
as the size and shape between both species.
Couthinho et al. (2012, 2015) investigated
morphology, anatomy and histochemistry of
the EFNs in Chamaecrista sect. Absus and they
clarified structural diversity of the EFNs as
well as their features of secretion. Although no
histochemical tests were applied in the present
study, two parenchyma areas similar to the
EFNs of sect. Absus were found in the EFNs
of C. mimosoides and C. nomame: the distal
non-vascularized area, which is composed of
parenchyma with dark-stained cells, appears
to correspond to the “nectary parenchyma” of
sect. Absus (Couthinho et al. 2012, 2015), and
the proximal vascularized area without dark-
stained cells corresponds to the “subnectary
parenchyma”. The central area of the top of the
EFN, where the epidermis was more or less
elevated, is assumed the site of nectar exudation
also in C. mimosoides and C. nomame.
Two types of vascularization toward
the EFNs were reported in the sect. Absus
(Couthinho et al. 2012, 2015): vascularization
supplied either from accessory vascular bundles,
which correspond to the ridge bundles in the
present study, and that from the median vascular
cylinder of the rachis. The former vascularization
was observed in Chamaecrista mimosoides and
the latter in C. nomame in the present study. The
vascular tissues of these two species are also
mainly composed of phloem cells like the EFNs
in the sect. Absus.
Structural relationships between crenate-crested
and canaliculate leaf rachises
The crenate-crested leaf rachis of Chamae-
crista mimosoides is initiated as a single
protuberance on the adaxial surface, whereas the
canaliculate one of C. nomame is initiated as two
parallel ridgelines. Both types of leaf rachises are
different from their initiation of development.
The vascular system between leaet pairs is also
different in both species, there is a single ridge
bundle in C. mimosoides and two separated
ridge bundles in C. nomame. In C. mimosoides,
however, the single ridge bundle partly divides
into two ridge bundles in the region between
leaflet pair when approaching to the region of
leaet insertion. Then, the two bundles are fused
December 2016 Nemoto et al.: Anatomy and development of leaves in Chamaecrista 213
into a single bundle again after connecting with
leaflet traces in the region of leaflet insertion.
Although the developmental process does not
imply the structural relationship between two
types of leaf rachis, the vascular system appears
to imply that the rachis with a pair of ridge
bundles is original state and that the crenate-
crested rachis is formed by the fusion of two
ridges as considered by Lock (2007). According
to Lock (2007) the top of the crest becomes
flattened, sometimes with two rows of hairs in
some regions of Africa, although the margins are
rmly fused so that there is no groove between
them. For understanding structural relationships
of two rachis types further anatomical studies on
these variations will provide useful evidence.
It is noteworthy that the parenchyma cells
in the crenate-crested protuberance are rich in
chloroplasts and there are many stomata present
in the epidermis in Chamaecrista mimosoides.
This implies that the unique crenate-crested
protuberance in the genus is related with
improvement of the function of photosynthesis.
Because leaves and leaflets of C. mimosoides
are obviously smaller than C. nomame and other
related species of the genus, the crenate-crested
protuberances appear to increase whole leaf area
of one leaf for photosynthesis.
Systematic implication of crenate-crested leaf
rachis
The present study claried the anatomical and
developmental features of the unique crenate-
crested leaf including the parts of pulvinus,
petiole, EFN and rachis in Chamaecrista
mimosoides and revealed differences in these
features from the common canaliculate leaf of
C. nomame. Although there was the opinion that
these two species are conspecific (e.g., Baker
1878, Matsumura 1902, Makino 1917, Ohashi
1966, 1982), the present evidence supports the
treatment of them as two different species (e.g.,
Honda1938, Ohashi 1989, Huang and Ohashi
1993, Singh 2001, Ohashi et al. 2013, Ohashi
2016).
The unique crenate-crested leaf rachis
was recognized as an important taxonomic
characteristic for Chamaecrista mimosoides
by Ghesquière (1932, as Cassia), and then
Steyaert (1950, as Cassia) mentioned the utility
of the rachis character for distinguishing species
in Asian and African Chamaecrista. Brenan
(1967) described the crenate-crested leaf rachis
in four species of African Chamaecrista (as
Cassia exilis Vatke, Cassia gracilior (Ghesq.)
Steyaert, Cassia mimosoides L. and unknown
Cassia sp. B). He, moreover, recognized huge
variation within Chamaecrista mimosoides (as
Cassia mimosoides) in Africa and distinguished
seven groups, called Groups A–G without
giving their names, within the species. In
Madagascar Du Puy (2002) recognized
10 species, five of which have the crenate-
crested leaf rachises. Although Ghesquière
(1935) and Viguier (1949) attributed some of
them to Chamaecrista mimosoides (as Cassia
mimosoides), Du Puy (2002) distinguished
them from C. mimosoides at species level with
recognition their closer relationships with the
Chamaecrista mimosoides complex in Africa.
The Chamaecrista mimosoides’ complex in
Africa and Madagascar appears to be important
materials for understanding structural variation
and systematic implication of the crenate-crested
leaf rachis.
With respect to New World Chamaecrista,
Steyaert (1950) mentioned the similar crenate-
crested leaf rachis present in Chamaecrista
flexuosa (L.) Greene (as Cassia flexuosa L.).
Irwin and Barneby (1982) established the
new ser. Flexuosae under Chamaecrsita sect.
Chamaecrista in having the leaf rachis as
narrowly winged between leaet pairs as one of
the important characteristics. However, except
for this characteristic there are no characteristics
supporting closer relationships between
C. mimosoides of Asia and Africa and ser.
Flexuosae of New World. The crenate-crested
rachis may be evolved independently in both
regions.
214 The Journal of Japanese Botany Vol. 91 Centennial Memorial Issue
Because the crenate-crested leaf rachis is rare
in the genus Chamaecrista and the species with
the canaliculate leaf rachis is located at the base
in a recent molecular phylogenetic tree including
Indian Cassia, Senna and Chamaecrista
(Seethapathy et al. 2015), the crenate-crested
leaf rachis is considered to be apomorphic in
Chamaecrista. For clarifying the systematic
implication of these characteristics in details,
morph-anatomical investigations and molecular
phylogenetic analyses are needed on the whole
of Chamaecrista sect. Chamaecrista as well as
the C. mimosoides complex, especially in Old
World.
We are grateful to Yoichi Tateishi (University
of the Ryukyus), Yasuhiko Endo (Ibaraki
University), Tadashi Kajita (University of the
Ryukyus), Tao Chen (Fairy Lake Botanical
Garden, Shenzhen & CAS), Binhui Chen,
Fuwu Xing, Huagu Ye (South China Botanical
Garden, CAS) and Chiajui Chen and Xiangyun
Zhu (State Key Laboratory of Systematic
and Evolutionary Botany, IB, CAS) for their
cooperation during the eld trip in South China
performed in 1993. This study was supported
in part by Grant-in-Aid for Scientific Research
from the Japan Society for the Promotion of
Science (No. 04041019 to H. Ohashi).
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216 The Journal of Japanese Botany Vol. 91 Centennial Memorial Issue
根本智行 a,大橋広好 b 德cマメ科ジャケツイ
バラ亜科カワラケツメイ属 Chamaecrista mimosoides
よび C. nomame における葉の解剖および発生
 カワラケツメイ属Chamaecrista mimosoides (L.)
Greene は東アジアからアフリカまで分布し,葉は比較
的小型の小葉をつける偶数羽状複葉で,約 80 対にまで
達する多数の小葉対からなる.さらに,葉軸の小葉対と
小葉対の間の向軸側に特異な半円形の円鋸歯型隆起を
もつことで,近縁種から識別されてきた.カワラケツ
メイ属植物の葉軸は,一般に,小葉対と小葉対の間の
向軸側に 2列の畝状の隆起があり,中央には溝ができ
る.C. mimosoides にみられる円鋸歯型葉軸はたいへん
希な特徴であるが,溝型葉軸との構造的な関連について
詳細は知られていない.本研究では,C. mimosoides
同じ Sect. Chamaecrista に属し,一般的な溝型葉軸をも
ち,かつては同一種として扱われることもあったカワラ
ケツメイ C. nomame (Makino) H. Ohashi と解剖学的お
よび発生学的に比較することで,両者の構造的な関連を
明らかにすることを目的とした.
 Chamaecriata mimosoides の円鋸歯型隆起は葉緑体を
多く含む単一の柔組織からできており,C. nomame
溝型葉軸の 2列の隆起はそれぞれ独立した柔組織から
できている.両者は発生過程初期から異なっており,前
者では単一の隆起が,一方後者では 2つの隆起が生じた.
どちらも葉柄の中央脈から向軸側の隆起に 2本の稜維管
(ridge bundle)が供給される.しかし,円鋸歯型葉軸
では小葉の付着点の直後に 1本に融合し,次の小葉付着
点までの中央付近で,再度 2本に分岐し,次の小葉付着
点を過ぎると再度一本に融合する.溝型葉軸では,葉軸
中で稜維管束は 2本のままである.また,円鋸歯型葉軸
では,融合した稜維管束から隆起に向かって分枝する 1
本の小さな維管束が確認された.葉柄の先端部にはどち
らも花外蜜腺を 1個もつが,C. mimosoides では稜維管
束から花外蜜腺に,C. nomame では中央維管束の両端
から,いずれも主に篩部からなる維管束が供給される.
 本研究の結果は,これまで同一種とする見解もあった
C. mimosoides C. nomame を区別する新規の形質を明
らかにした.また,円鋸歯型葉軸の 2本の稜維管束が
小葉付着点間で融合と分岐を繰り返す走向パターンは,
円鋸歯型葉軸が溝型葉軸の 2列の畝が合着してできた
とする Lock (2007)の考えを支持した.さらに,円鋸歯
型隆起を構成する柔組織に多数の葉緑体が含まれ,表皮
に多数の気孔が観察されることから,円鋸歯型葉軸は葉
の光合成能力の向上に係わっていることが示唆された.
a石巻専修大学理工学部生物科学科,
b東北大学植物園津田記念館,
c中国科学院華南植物研究所)
Peninsulae Indiae Orientalis 1. Parbury, Allen, & Co,
London.
Zhu X. Y., Du Y. F., Wen J. and Bao B. J. 2007. Legumes
of China: a Check-list. The ILDIS at the School
of Biological Sciences, the University of Reading,
Reading.
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A newsletter to promote communication among research scientists concerned with the systematics of the Leguminosae/Fabaceae
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Sooya nomame Siebold, the intended basionym of Chamaecrista nomame, had been treated as a validly published name, but is merely a designation, whereas Cassia mimosoides van nomame Makino was validly published in 1917. Chamaecrista nomame (Makino) H. Ohashi emend. H. Ohashi, T. Nemoto & K. Ohashi is proposed here by emending Chamaecrista nomame (Siebold) H. Ohashi to exclude Senna dimidiata Roxb. and Cassia hochstetteri Ghesq. from its synonyms. We recognize Chamaecrista nomame is distinct from Chamaecrista dimidiata (Roxb.) Lock. These species are distinguished from each other in legumes (3-4 cm long, 5-6 mm wide, and (8-)10(-12)-seeded in C. nomame, while 4-5 cm long, 4-5 mm wide, and (13-)15-16(-20)-seeded in C. dimidiata), pedicels (6-8 mm long in C nomame, while 10-15 mm long in C. dimidiata), and seeds (3.5-4 × 2.5-3 mm in C. nomame, while 2.5-3 ×1.5-2 mm in C. dimidiata). Chamaecrista nomame is distributed in Japan, Korea and E. & NE. China. The neotype of Cassia mimosoides var. nomame Makino is designated. Synonyms of the emended Chamaecrista nomame are enumerated with bibliography. Senna nomame (Makino) T. C. Chen is newly regarded as a synonym of Chamaecrista nomame, because the species belongs to Chamaecrista in having bracteoles on the pedicel and coiling valves.
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Chamaecrista (L.) Moench (Caesalpinioideae-Leguminosae) with 330 species is organized into six sections: Apoucouita, Absus, Grimaldia, Chamaecrista, Caliciopsis and Xerocalyx. Section Absus is the largest section of the Chamaecrista and is organized into four subsections, viz., subsect. Adenophyllum, subsect. Baseophyllum, subsect. Otophyllum and subsect. Absus. This section is not monophyletic and has a complex taxonomy. This study aims to anatomically characterize 60 taxa of Chamaecrista, identifying meaningful morphoanatomical characters that may shed light on the evaluations of the taxonomic and phylogenetic framework of Chamaecrista, especially C. sect. Absus. Standard light microscopy techniques were used to anatomically characterize the leaves. The anatomical data were subjected to a multivariate analysis (Jaccard index). Epidermal papillae on the abaxial side, the distribution and types of secretory and tector trichomes, variations in the arrangement of the vascular system of the midvein and the type of arrangement of the vascular system of the petiole are useful for separating species or groups of species. The presence and type of secretory structure, the type and position of stomata and the venation pattern are important in establishing the affinities between sections and subsections. The phenetic analysis demonstrates that the anatomical data contribute to the establishment of affinities between sections and subsections, supporting the elevation of the taxonomic status of the clade Baseophyllum to section and the insertion of C. absus (C. sect. Grimaldia) into C. sect. Absus, corroborating molecular studies.
Article
Some easily seen structural features of living plant cells are destroyed or badly distorted by most of the common fixatives and embedding media used in plant histology. In stained sections of plant tissues fixed in FAA (formalin-acetic acid-alcohol mixtures) and embedded in paraffin wax, for example, mitochondria and fine transvacuolar strands of cytoplasm are usually not visible. Many structural features such as these can be preserved, however, with suitable fixatives and embedding media. Specifically we recommend fixation in non-coagulant fixatives (e.g., osmium tetroxide, acrolein, glutaraldehyde, formaldehyde) and the use of plastics as embedding media, and we describe in detail a method of fixation in acrolein and embedding in glycol methacrylate polymer. In a wide range of plant specimens prepared in this way, stained sections 1–3 microns thick showed excellent preservation of tissue and cell structures.
Article
Section Apoucouita (Chamaecrista (L.) Moench – Caesalpinioideae) is an arboreal group that is most diverse in the Amazon and Brazilian Atlantic forests. These species typically bear petiolar and (or) rachis glands called extrafloral nectaries (EFNs). However,no detailed anatomical studies or histochemical analyses have been conducted to confirm nectar secretion. We aimed at describing the structure of such EFNs, as well as determining the chemical nature of the secretion. Eighteen species (23 taxa) were studied using standard light microscopy techniques. We describe 13 types of EFNs with variable morphology. Such EFNs may be impressed, sessile, or stalked; with concave, flat or truncate, or convex secretory surfaces. Cupuliform EFNs (stalked or not) were the most common type observed and patelliform the least common. Despite the morphological variation, differences in the anatomical structure of the EFNs and the chemical composition of the secretion were not observed. EFNs with concave secretory surfaces appear to be more effective as nectar may become accumulated in the concavity, increasing the volume of available nectar. Our results show that despite the variable morphology of the EFNs, such structures share similarities on the anatomy and composition of the secretion and development of a wound-healing periderm inolder EFNs.We also indicate the importance of including the morphological variation observed in the EFNs in species of sect. Apoucouita in future taxonomic evaluations. © 2015 National Research Council of Canada . All Rights Reserved.
Article
RIASSUNTO Vengono descritte le specie di Cassia L. presenti in Malesia e di esse viene data la chiave analitica. Risulta che relativamente poche sono le specie di Cassia indigene in Malesia; molte sono d'incerta origine. La maggior parte delle specie indigene appartengono al sottogenere Cassia (o « Fistula »). La maggior parte delle specie sono coltivate (come ornamentali) o si trovano come piante infestanti. Il centro di sviluppo dell'eterogeneo genere Cassia L. sembra che sia nel Sud-America (ad eccezione forse del sottogenere Cassia) ed appare consigliabile percio di non tentare o adottare una suddivisione di Cassia L. in generi distinti. Viene qui adottata la delimitazione dei sottogeneri proposta da BENTHAM. Viene descritta una nuova specie, Cassia pachycarpa, della Nuova Guinea; e vari taxa infraspecifici sono proposti come nuovi, o rinominati in seguito a cambiamenti del rango sistematico. Tutti i taxa vengono tipificati conforme alle regole prescritte dal Congresso di Stoccolma (1950).
Article
Premise of research. Colleters are structures that secrete a sticky product that covers and protects the shoot apex and floral buds. In Chamaecrista, colleters have been reported in the cotyledons of three species and on the leaves of all species belonging to sect. Absus subsect. Baseophyllum. Anatomical studies using taxonomic and phylogenetic approaches are necessary to evaluate the presence, diversity, and importance of colleters for Chamaecrista. Methodology. We analyzed 55 species of Chamaecrista belonging to five of the six sections of the genus. Samples from both herbarium- and field-collected material of young vegetative and reproductive meristems were used. The material was subjected to standard anatomical study by light microscopy and SEM, and secretion was evaluated by histochemical analyses. Pivotal results. Histochemical analyses for the total proteins, total polysaccharides, acid mucopolysaccharides, pectins/mucilage, and lipids generated positive results. Six types of colleters are described here: club shaped, racket shaped, long bottle shaped, short bottle shaped, long digitiform, and short digitiform. Sect. Apoucouita showed the short digitiform and club-shaped types and was the only section with colleters on the sepal margins. Most species of sect. Absus subsect. Absus presented the short bottle-shaped type, while all species from subsect. Baseophyllum presented the short digitiform and club-shaped types. Although the short bottle-shaped type was the most common among species from sect. Chamaecrista, the short digitiform and club-shaped types were also observed. The short bottle-shaped colleters were also found in sect. Grimaldia, while in sect. Xerocalyx only the digitiform type was found. Conclusions. The topography and components identified in the secretion of the colleters suggests that such structures may be involved in the protection of developing leaves and flowers. Five of the six types described in our study are novelties for Chamaecrista. The distribution of colleter structural diversity provides an important source of new data that may help to clarify the taxonomy and phylogeny of Chamaecrista. Keywords: anatomy, buds, histochemical test, secretory structures, shoots, trichomes.