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45
PHYTOLOGIA BALCANICA 27 (1): 45 – 58, Sofia, 2021
Morphological, anatomical and histological studies on the
genus Icacina (Icacinaceae) from Nigeria, West Africa
Chimezie Ekeke, Thankgod Onyemuche Joseph & Stephen Ikechukwu Mensah
Department of Plant Science and Biotechnology, Faculty of Science, University of Port
Harcourt, PMB 5323, Choba, e-mail: ekeke.uche@uniport.edu.ng, ekeke.uc@gmail.com
(corresponding author)
Received: August 11, 2020 ▷ Accepted: March 17, 2021
Abstract. Morphological, anatomical and histological studies of three Icacina species (I. mannii Oliv., I. oliviformis
(Poir.) J. Raynal, and I. trichantha A. (Juss)) were carr ied out by visual obser vation and microscopy. The species
occur predominantly in Nigeria, West Africa. They exhibited anatomical variation in the midrib vascular
bundle arrangement, trichome types and abundance, stomatal types, lamina thickness, stomatal index, and
fruit morphology, all regarded as reliable diagnostic characters. Only I. oliviformis manifested druses and
galls. The study revealed some morphological and anatomical similarities, such as leaf arrangement, non-
glandular trichomes, anomocytic and tetracytic stomata, epidermis cell shape, and presence of tannin and
starch grains in the corms of the species.
Key words: Anatomy, druses, histology, Icacina, stomata index, trichome.
Introduction
Icacinaceae is a pan-tropical family of trees, shrubs and
lianas, with 50–55 genera and 300–400 species world-
wide (Mabberley 1997; Kårehed 2001). Studies have
shown that the family, as traditionally circumscribed,
was polyphyletic (Savolainen & al. 2000; Soltis & al.
2000; Kårehed 2001). This resulted in a morpholog-
ically heterogeneous group, difficult to recognize in
the field and in herbariums (van Balgooy 1998). Based
on molecular phylogenetic work, the family has now
been split into four families: Icacinaceae s. str. (Garry-
ales), Pennantiaceae (a member of the order Apiales),
Cardiopteridaceae, and Stemonuraceae (both mem-
bers of the order Aquifoliales) (Kårehed 2001; Ste-
vens 2001). The family Icacinaceae A. Juss compris-
es about 35 genera, including the genus Icacina with
only three species, namely: I. mannii Oliv., I. olivi-
formis (Poir.) J.Raynal, and I. trichantha A. (Juss) in
West Africa (Hutchinson & Dalziel 1954). These spe-
cies are in abundance in some West African countries
such as Nigeria, Chad, Benin Republic, Gambia, and
Ghana. In West Africa, members of this genus have
several common names: Fa lse Yam in the Anglophone
countries, Bakanas in the Francophone countries, and
in Nigeria they are called Ibugo or Utu by Igbos, Gbe-
gbe by the Yorubas, Pane in Sudan, Ta kwa ra in Gha-
na, and Kouraban in Senegal (Burkill 1985; Fay 1987).
The Icacina species could be used as a food source
because of the nutritional contents of their seeds: 13 %
moisture, 72 % carbohydrates, 8–10 % protein, 0.1 %
fat, and 0.5 % (Fay 1991). Fine flour domestically made
from the tubers contains on the average 10–15 % of
starch, which could either be spherical or elliptical (Fay
1973). The roots are toxic and are used in traditional
medicine after detoxifying according to local means
by macerating them in water or ethanol for about
three days (Fay 1973). The paste or porridge made
from the tubers of Icacina species contains 8–10 %
protein, about five (5) times more than in the cassava
flour and twice more than in potatoes (Fay 1991).
The pharmacological uses and medical potential of
the species are well documented (Sarr & al. 2011).
I. oliviformis is used for treatment of Plasmodium,
46 Ekeke, Ch. & al. • Studies on the genus Icacina from Nigeria
due to its active antiplasmodial effect without host
cell toxicity. It also contains dichloromethane, a very
strong antimicrobial agent and thus is very promising
in medical research against malaria (Sarr & al.
2011; Okoronkwo & al. 2014). I. trichantha contains
different phytochemicals of economic importance
(Ezeigbo 2010; Timothy & Idu 2011; Onakpa & Asuzu
2013; Shagal & al. 2014). In many communities,
these species are misidentified, owing to their close
resemblance based on morphological similarity. They
are cultivated by tuber cutting (Mabberly 1997).
Leaf epidermal structures of some Icacinaceae spe-
cies have been studied and described by different au-
thors (Metcalfe & Chalk, 1979; Baas 1974; van Staveren
& Baas 1973; Heintzelman & Howard 1948). Cuticu-
lar characters have been employed in the classification
of sterile material down to the genus level in the Male-
sian Icacinaceae, including 28 genera outside Malesia
(van Staveren & Baas 1973; Baas 1974). Contributions
to leaf anatomy, other than epidermal structure, are
scanty and relatively superficial (Solereder 1908; Sca-
la 1917; Gerhard 1902), or have been neglected in sys-
tematical works on the Icacinaceae (Potgieter & van
Wyk 1999). Lens & al. (2008), consequently, report-
ed that the wood structure and anatomical characters
of the stem of this family (including the genus Icaci-
na) could be regarded as key features for intrafamily
classification.
Among the African Icacinaceae, Potgieter & van
Wyk (1999) have studied and described the leaf anato-
my of eight species from the genera Apodytes, Cassin-
opsis and Pyrenacantha, which are trees and shrubs.
Though Potgieter & van Wyk (1999) worked on these
genera, the genus Icacina was not part of their study.
Earlier studies have focused only on the wood struc-
ture and anatomical characters of I. mannii and I. clas-
seni from West Africa (Lens & al. (2008). It has been
difficult to distinguish the other members of the ge-
nus because of their close morphological characters
(Akobudu & Agyakwa 1998; Akobudu & al. 2016).
The epidermal structure, leaves and anatomy of the
West African species of the genus Icacina are yet to
be described. Therefore, this research work is aimed
at describing the morphological features, epidermal
characteristics, leaf anatomy, and histological charac-
ters of I. mannii, I. oliviformis, and I. trichantha, in or-
der to aid the identification of these three species in
West Africa.
Material and methods
Sample collection and study area
Samples of the Icacina species were collected from
the environs of the University of Port Harcourt,
Nigeria (University of Port Harcourt Biodiversity
Con servation Centre and Faculty of the Agriculture
Farm). The plants were properly identified, processed
and deposited in the University of Port Harcourt
Herbarium (Table 1). The analysis was carried out
in the Plant Taxonomy and Biosystematics Research
Laboratory, Department of Plant and Biotechnology,
Faculty of Science, University of Port Harcourt,
between February 2015 and April 2020.
Table 1. Voucher specimens of the studied Icacina species.
Species
name
Locality Collection
date
Name(s) of
collector
Herbarium
number
I. oliviformis University of
Port Harcourt
Biodiversity
Conservation
Centre
10/05/2019 Ekeke, C. &
Joseph, T. O.
UPH/1123
I. mannii University of
Port Harcourt
Biodiversity
Conservation
Centre
20/05/2019 Ekeke, C. &
Joseph, T. O.
UPH/1402
I. trichantha Faculty of
Agriculture Farm,
University of Port
Harcourt
04/07/2019 Ekeke, C. &
Nichodemus,
C. O.
UPH/1056
Morphological study
The quantitative characters of the vegetative and re-
productive parts were measured and recorded. Such
traits like habit, habitat, leaves arrangement and type,
morphology (leaf length, leaf width, petiole length,
and degree of hairiness), inflorescence and flower,
scent, hairiness, friut (size and hairiness), and size of
tubers were recorded from 100 plant specimens. The
range and average values were calculated using Micro-
soft Excel 2010. The terminology for the morphologi-
cal description followed Hutchinson & Dalziel (1954),
Davis & Heywood (1973), and Priti & Shital (1979).
Photographs of the plants were taken and document-
ed by a Canon digital camera.
Epidermal studies
Fresh foliar material for epidermal studies was collect-
ed from plants growing in the wild. The adaxial and
abaxial epidermises were peeled, stained with 1 %
47Phytol. Balcan. 27(1) • Sofia • 2021
Safranin or Alcian Blue, rinsed with distilled water
to remove excess stain, mounted in a drop of pure
glycerine on clean glass slides, placed under coverslips
and sealed with nail varnish to prevent dehydration
(Okoli & Ndukwu 1992). Twenty good slides were
observed using a trinocular research microscope
(T340B) fitted with Amcope digital camera. The
epidermal features followed Metcalfe and Chalk (1979)
determinations and the stomatal types are according
to Malvey (2004) and Dilcher (1974). The length and
width of 200 stomata and their complex were measured
with graticule, and recorded. The mean and standard
deviation was calculated by Microsoft Excel 2010.
Anatomical studies
One hundred (100) slides from twenty petioles,
midribs, roots, and corms from mature plants and
young stems were prepared and observed. The
samples were fixed in FAA (formaldehyde: glacial
acetic acid: ethanol in the ratio of 1:1:18 parts of
70 % ethanol v/v) for at least 48 hours. The samples
were washed in several changes of distilled water,
dehydrated in alcohol series (30 %, 50 %, 70 %,
and 100 %) solution for two hours per series and
embedded in wax. Sections were cut with a Leitz
1512 rotary microtome, with thickness between 15–
20 µm. The selected sections were de-waxed and
stained with 1 % Safranin O and counterstained with
Alcian Blue, mounted on slides and micro-photo-
graphed with a trinocular research microscope
(T340B) fitted with Amcope digital camera.
Histological localization of tannin
Thin microtome sections were fixed in a mixture of
iron II sulphate and formalin (FeSO4 + formalin).
The darkly stained areas indicated the presence and
occurrence of tannin (Okoli 1988).
Histological localization of starch
The test for starch was limited to only the corm of each
species of Icacina species. Cut sections of the corms
were stained with a mixture of potassium iodide and
iodine (KI + iodine). The presence, distribution, and
localization of starch grains in the different areas of the
corm were noted and recorded, and photomicrographs
were taken using a trinocular research microscope
(T340B) fitted with Amscope digital camera.
Results
Macro-morphological description
I. mannii (Fig. 1). A scandent forest and forest re-
growth, and swamp-forest shrub, 0.8–3.4 m high,
leaves alternate and leaf stalks 0.4–1.2 cm long
(Fig. 1a). Leaves broadly obovate-elliptic, abruptly
acuminate at apex, more or less cuneate or acute at
base, 11.3–22.5 cm long and 5.4–12.0 cm wide, gla-
brescent or sparsely hairy beneath. Flowers sessile,
5-merous, creamy, with scent, occurring in axillary/
terminal clusters or short dense cymes towards the
apex of the stem (Fig. 1b). Calyx much shorter than
the petals; petals appressed-pubescent outside. Fruits
Fig. 1. Morphological features of I. mannii (a) habit, (b) inorescence, (c) unripe fruits, (d) corm.
48 Ekeke, Ch. & al. • Studies on the genus Icacina from Nigeria
very hairy, rough, 2.0–2.5 cm long, and 1.4–2.0 cm
wide (Fig. 1c). The tubers large and cylindrical, and
weigh 0.2–0.4 kg (Fig. 1d).
I. oliviformis (Fig. 2). A forest, forest regrowth
and swamp-forest scandent shrub, with glabrous
to partly pubescent stem, 0.3–0.9 m tall or more,
leaves alternate and leaf stalks 0.6–2.0 cm long
(Fig. 2a). Leaves lanceolate to obovate, base acute,
apex acuminate to cuspidate and emarginate, 13.4–
22.2 cm long, 7–114.2 cm wide, conspicuously reti-
culate and glabrous or nearly so, with galls (Fig. 2b).
Flower 5-merous, creamw, on a short stalk, occurring
in axillary clusters or short dense cymes; calyx
short; petals shortly hairy outside. Fruits bright-
red, obovoid to ovoid berries measuring about 2.5–
3cm in length and 2–2.5cm in width, tomentellous,
slightly wrinkled (Fig. 2c). The large underground
fleshy tuber (corm) oval and weighs about 1.5–2.5
kg (Fig. 2d)
I. trichantha (Fig. 3). A forest and forest regrowth
scandent shrub, leaves alternate, leaf stalk 0.7–
1.7 cm long (Fig. 3a). Leaves broadly elliptic or ob-
long, abruptly acute or cuspidate at the apex, round-
ed or cordate at base, 13.6–25.0 cm long, 5.7–13.3 cm
wide, lower surface covered with long, non-glandu-
lar, fascicled-soft hairs. Flowers densely crowded on
a stalk 2–3.5 cm long, subsessile and occurring on
the older stem (Fig. 3b), creamy (Fig. 3c), calyx 0.2–
0.4 mm long, nearly as long as the petals (Fig. 3c).
Ripe fruits red and unripe fruits green; the under-
ground tuber (corm) very large, oval and weighs 0.3–
0.5 kg (Fig. 3d).
Fig. 2. Morphological features of I. oliviformis (a) habit, (b) leaves showing galls and ower, (c) ripe and unripe fruits and (d) corm.
Fig. 3. Morphological features of I. trichantha (a) habit, (b and c) inorescence, (c) and (d) corm.
49Phytol. Balcan. 27(1) • Sofia • 2021
Leaf epidermal characteristics
All studied Icacina species have dorsiventral leaves
and are hypostomatic (Figs 5-10 and Table 2). Stoma-
tal index varied among the species: I. manni (28.33), I.
oliviformis (15.29), and I. trichantha (8.77). Stomatal
complex (guard cells and subsidiary cells) of the spe-
cies ranged from 25.70–29.29 µm in length to 22.34–
30.07 µm in width (Table 2). The adaxial epidermis
of the leaves of all three species had cyclocytic and
anomocytic stomata. Furthermore, I. oliviformis and
I. mannii have tetracytic stomata, while I. trichantha
has staurocytic stomata. The abaxial epidermal cells
of the three Icacina species are pentagonal to polygo-
nal, with straight to curved anticlinal walls. The abaxi-
al epidermal cells have polygonal to irregular in shape,
with wavy anticlinal walls (Figs 5-10 and Table 3).
Figs 5-10. Epidermal characteristics of Icacina species: (5) Upper epidermis of I. mannii with polygonal epidermal cells, (6) Lower epidermis
of I. mannii with irregular epidermal cells, (7) Upper epidermis of I. oliviformis, (8) Lower epidermis of I. oliviformis, (9) Upper epidermis
of I. trichantha, (10) Lower epidermis of I. trichantha with irregular epidermal cells and undulating anticlinal walls. Cy – cyclocytic stomata,
St – staurocytic stomata, An – anomocytic stomata.
50 Ekeke, Ch. & al. • Studies on the genus Icacina from Nigeria
Petiole anatomy
Generally, the petiolar vascular bundles of all three
studied species have invaginated ends forming an is-
land (Figs 11-13, Table 4). They are hairy in I. man-
nii (Fig. 11a), partly hairy or glabrous in I. oliviformis
(Fig. 12a), and very hairy in I. trichantha (Fig. 13a).
The shape of the petioles varied slightly among the
studied species. For instance, the shape of the petiole
is circular in I. mannii and I. oliviformis, but oval in I.
trichantha. The adaxial cuticle outline in I. trichantha
is convex, V-shaped in I. oliviformis, and flat/concave
in I. mannii.
Midrib anatomy
The midrib of all three species contained deeply stained
fibres, as well as xylem and phloem tissues. The outline
of the adaxial midrib of I. mannii is flat (Fig. 14a),
concave in I. oliviformis (Fig. 15a), and flat to convex in
I. trichantha (Fig. 16a). The vascular bundles in midrib
formed a closed semi-circle in I. mannii and I. oliv iformis
Table 2. Stomatal size, index and types in the studied Icacina species.
Species
name
Leaf
surface
Stomata
type
Stomatal
index
Stomatal size (µm) Stomatal complex (µm)
Length Width Length Width
I. mannii
Abaxial Tetracytic, cyclocytic, and anomocytic. 28.33 21.17–31.75
(25.70±2.99)
26.46–31.75
(27.71±2.28)
40.24–85.56
(64.39±9.99)
40.92–84.40
(58.48±9.29)
Adaxial – – – – – –
I. oliviformis
Abaxial Tetracytic, cyclocytic, and anomocytic. 15.29 22.49–28.63
(25.78±1.87)
19.95–24.77
(22.34±1.93)
36.41–102.77
(56.50±19.83)
29.16–61.38
(42.29±10.62)
Adaxial – – – – – –
I. trichantha
Abaxial Tetracytic, anomocytic, and staurocytic. 8.77 24.67–35.00
(29.29±2.89)
20.99–36.47
(30.07±2.94)
48.08–77.82
(61.99±8.28)
47.27–68.55
(57.99±5.92)
Adaxial – – – – – –
Table 3. Description of epidermal cells and trichomes in the studied Icacina species.
Species
name
Leaf
surface
Epidermal
cells
Trichome
Typ e Abundance Epidermal size (µm)
Size (µm) Length Width
I. mannii
Adaxial Irregularly shaped anticlinal walls Simple non-glandular
unicellular hairs and
sessile stellate hairs
++ 8.1–76.0
(32.4±26.2)
15.88–42.33
(29.48±6.93)
5.29–21.17
(12.09±3.56)
Abaxial Pentagonal to hexagonal, with
straight to curved anticlinal walls
++ 10.58–31.75
(22.42±5.70)
10.58–21.17
(13.73±3.32)
I. oliviformis
Adaxial Polygonal to irregular in shape,
with wavy anticlinal walls Simple non-glandular
unicellular hairs
+ 51–146
(66.3±27.1)
22.75–61.33
(36.73±8.51)
9.68–28.15
(20.39±4.76)
Abaxial Pentagonal to hexagonal, with
straight to curved anticlinal walls
+ 13.90–40.90
(25.39±5.82)
8.10–19.39
(13.48±3.75)
I. trichantha
Adaxial Irregularly shaped anticlinal walls Simple non-glandular
unicellular hairs and
short-stalked stellate hairs
+++ 25.6–106
(67.7±28.5)
17.10–36.00
(25.31±5.01)
8.30–21.20
(13.93±2.87)
Abaxial Pentagonal to polygonal, with
straight to curved anticlinal walls
+++ 12.37–29.38
(21.59±4.17)
7.19–18.66
(13.11±2.18)
Keys: + = present, ++ = abundant and +++ = more abundant.
Table 4. Characteristics of the lamina in the studied Icacina species.
Plant part I. oliviformis I. mannii I. trichantha
Layers of spongy mesophyll 1 1–2 1–2
Layers of palisade mesophyll 6–8 7–8 8–9
Thickness of lamina (µm) 142–147 34–35 38–40
Percentage of palisadecells 13.53–17.02 24.68–25.70 15.85–16.45
Nature of palisade mesophyll Loosely packed, 16–28 µm thick Closely packed, 37.03–47.61 µm thick Closely packed, 39.03–47.61 µm thick
Nature of spongy mesophyll Loosely packed with air spaces,
armed cells, 86–96 µm thick
Loosely packed with air spaces, armed
cells, 111.09–121.67 µm thick
Loosely packed with air spaces, armed
cells, 132.25–142.83 µm thick
Upper epidermis 1-layer, periclinally elongated,
13–24 µm long, 9–12 µm thick
1-layer, oval in shape, 5.29–15.87 µm
long, 10.58 µm thick
1-layer, oval in shape, 5.29–15.87 µm long,
10.58 µm thick
Lower epidermis 1-layer, periclinally elongated,
13–24 µm long, 9–12 µm thick
1-layer, 10.58 µm long, 5.29–10.58 µm
thick
1-layer, periclinally elongated,
10.58–15.87 µm long, 5.29–10.58 µm thick
51Phytol. Balcan. 27(1) • Sofia • 2021
(Figs 14a and 15a), but with two adaxial rib traces in I.
mannii (Fig. 14b). In I. trichantha, the vascular bundle
formed a semi-circular arc with a central adaxial
cylinder (Fig. 16a). The cortex parenchyma in I. mannii
consisted of 7–8 layers, with crushed parenchyma
(Fig. 14c), 6–8 layers in I. oliviformis (Fig. 15b), and 16–
20 layers in I. trichantha (Fig. 16b).
Leaf lamina
The lamina of all studied species was dorsiventral and
the spongy mesophyll was loosely packed with air
spaces with epidermal mucilage (Fig. 17). The pali-
sade mesophyll cells in I. oliviformis were loosely
packed (Fig. 17b), while in I. mannii (Fig. 17a) and I.
trichantha (Fig. 17c) the palisade mesophyll cells were
closely packed. The bundle sheets were embedded in
the spongy mesophyll in I. oliviformis and I. trichan-
tha, but extended through the palisade mesophyll to
the adaxial epidermal surface in I. mannii.
Stem anatomy
The stem anatomy of all three Icacina species showed
persistent or patches of sclerenchymatous fibres in
the outside portions of the vascular bundles. The ves-
sels were pronounced, mainly solitary, with no visible
rays (Fig. 18). They occurred seldom in radial pairs or
multiples in I. mannii (Fig. 18a), in tangential and ra-
dial pairs in I. oliviformis (Fig. 18b), and in tangential
pairs and radial multiples of 2–6 vessels in I. trichan-
tha (Fig. 18c).
Figs 11-13. Transverse section of petiole; (11) I. mannii, (12) I. oliviformis, (13) I. trichantha, Pa – parenchyma, Xy – xylem, Ph – phloem,
Dr – druses, Co – cortex, Tr – trichome, Cu – cuticle.
52 Ekeke, Ch. & al. • Studies on the genus Icacina from Nigeria
Figs 14-16. Midrib anatomy of the studied Icacina species: (14) I. mannii, (15) I. oliviformis, (16) I. trichantha, Co – cortex, – bre,
av – adaxial vascular bundle, Tr – trichome, Xy – xylem, Pa – parenchyma, Ph – phloem, St – crystal cluster, Dr – druses, Cr – crushed
parenchyma, vb – vascular bundle, ep – epidermis, Cu – cuticle.
Fig. 17. Leaf lamina of the studied Icacina species: (a) I. mannii, (b) I. oliviformis, (c) I. trichantha (Note: St- stoma, Ar- air space, Lp-
lower epidermis, Sm- spongy mesophyll, bs- bundle sheet, up- upper epidermis, Pm- palisade mesophyll).
53Phytol. Balcan. 27(1) • Sofia • 2021
Root and corm anatomy
The roots of all species have some similar anatomical
features, namely, starch grains, tannins and secretory ca-
nals (Fig. 19). There is abundance of secretory canals in
I. mannii (Fig. 19a and b) and I. oliviformis (Fig. 19c and
d). I. trichantha has thick-walled sclereids, with obvious
secretory canals (Fig. 19e and f). The corms have patch-
es of vascular bundles containing tannins (Figs 33-35).
I. mannii had scanty thick-walled sclereids in the paren-
chymatous cortex (Fig. 33), and in I. oliviformis (Fig. 34)
and I. trichantha (Fig. 35), the thick-walled sclereids are
in abundance in the parenchymatous cortex.
Fig. 18. Stem anatomy of the studied Icacina species: (a) I. mannii, (b) I. oliviformis, and (c) I. trichantha, Pi – pith, Co – cortex, Scl – bre,
Ph – phloem, Xy – xylem, and arrows show vessels.
Fig. 19. Cross-section of Icacina roots: (a and b) I. mannii (arrows show secretory canals), (c and d) I. oliviformis (arrows show secretory
canals) and (e and f) I. trichantha (arrows show thick-walled sclereids), Sc – sclereids.
Calcium oxalate, tannins and starch distribution
In this study, calcium oxalate crystals (druses) are ob-
served only in the petioles (Fig. 12c) and midrib (Fig. 15b
and c) of I. oliviformis. Tannins are found mainly in stem,
midrib, petiole, and root of the species (Figs 20-34), while
starch grains mainly occurred in the corms (Figs 35-37).
Tannins are concentrated in the xylem vessels, with
patches in the endodermis, fiber cells, and parenchym-
atous cortex. The presence of these compounds (their
abundance) varied slightly amongst the species. Varia-
tion in concentration in the different parts of the plants is
presented in Table 5.
54 Ekeke, Ch. & al. • Studies on the genus Icacina from Nigeria
Figs 20-28. Tannin distribution is indicated by darkly stained areas in the petiole, midrib, and stem of the Icacina species: (20, 23 and 26)
I. mannii, (21, 24 and 27) I. oliviformis and (22, 25 and 28) I. trichantha.
Figs 29-34. Tannin distribution in the studied Icacina species: (29–31) root, (32–34) corm. Tannins are indicated by the darkly stained tissues:
(29 and 32) I. mannii, (30 and 33) I. oliviformis and (31 and 34) I. trichantha. Vb – vascular bundle containing tannins, and Sc – sclereids.
55Phytol. Balcan. 27(1) • Sofia • 2021
Figs 35-37. Starch distribution in the corm of the studied Icacina species: (35) I. mannii, (36), I. oliviformis and (37) I. trichantha.
Fig. 38. Trichomes observed in the Icacina species: (a-b) simple non-glandular unicellular trichomes, (c-h) stellate non-glandular trichomes.
Arrows show biseriate arms.
Trichome types
The trichomes observed in this study varied in types
and abundance among the species (Fig. 38, Table 3).
They included simple non-glandular, uncinate, and
multi-armed (sessile or short-stalked stellate) hairs.
Trichomes are more abundant in I. trichantha, fol-
lowed by I. mannii. I. oliviformis was the least hairy
(Table 3). The length of trichomes slightly varied
among the taxa. Simple non-glandular unicellular
hairs (Figs 38a and b) occurred in all studied species,
Table 5. Distribution of tannins and starch in the studied Icacina
species.
Compound Plant part Species name
I. mannii I. oliviformis I. trichantha
Tannin
Petiole + ++ +++
Stem ++ + +++
Midrib ++ ++ +++
Root ++ + +++
Corm + ++ +++
Starch Corm + +++ ++
Keys: + = present, ++ = abundant and +++ = more abundant.
56 Ekeke, Ch. & al. • Studies on the genus Icacina from Nigeria
as well as sessile stellate hairs. Sessile stellate hairs
with unicellular arms (Figs. 38c) and biseriate arms
(Fig. 38d and h) occurred in I. mannii, while short-
stalked stellate hairs with unicellular arms (Fig. 38
e-g) occurred in I. trichantha.
Discussion
In this research, such morphoanatomical characters
as the dorsiventral leaf, collateral vascular bundles,
presence of non-glandular trichomes (in the young
stems, leaves and petioles), starch grains, shape of the
epidermal cells, shape of the vascular bundles in the
petioles, alternate leaf arrangement, etc. are similar
in all Icacina taxa. However, the following characters
could be emphasized as useful to distinguish the
species: midrib vascular bundle arrangement, adaxial
outline of the petioles, percentage of palisade cells,
thickness of the lamina, presence or absence of druses
in the petiole and midrib, size of the epidermal cells,
stomatal type and size, stomatal index and complex.
Morphologically, the studied species could be dis-
tinguished by their leaf shape, size and shape of the
corms, fruit morphology (shape, size, wrinkles, and
hairiness), and position of the inflorescence.
In Icacinaceae, the differences found in the epi-
dermal characteristics, stomatal types, leaf and wood
anatomy have always been discussed at generic and
family levels (Bailey & Howard 1941; van Staveren
& Baas 1973; Baas 1974; Potgieter & van Wyk 1999;
Lens & al. 2008). The size of the epidermal cells on
both adaxial and abaxial leaf surfaces varied among
the species. In this study, the authors observed tetra-
cytic and anomocytic stomata in all species. However,
cyclo cytic stomata were only found in I. mannii, para-
cytic stomata in I. oliviformis and staurocytic stoma-
ta in I. trichantha. The existing reports by Pot gieter &
van Wyk (1999) on the leaf structure of three South
African genera of Icacinaceae using light and scan-
ning electron microscopy had shown that the stoma-
tal and trichome types, and lamina characters (such as
mucilage cells, pectic warts and ‘unidentified cell in-
clusions’) were diagnostic characters for these genera.
According to their findings, both Cassinopsis Sond.
and Pyrenacantha Hook. had cyclocytic stomata, as
opposed to the anomocytic type in Apodytes E. Mey.
Ex Arn. The presence of a stomatal ridge in A. dimi-
diata was a useful character in separating this species
from the other two South African members of that
genus. Also, in the epidermal characters of 109 spe-
cies of the Malesian Icacinaceae and the genus Pen-
nantia from Australia and New Zealand, great diver-
sity was encountered in the stomatal types, including
para cytic, anomocytic, cyclocytic, anisocytic, helico-
cytic, and several intermediate stomata types. The
paracytic and anomocytic stomata were restricted to
a few genera and were primitive for the family, while
the cyclo cytic stomata were most frequent in the dif-
ferent genera (van Staveren & Baas 1973; Baas 1974).
In another study based on a comparative anatom-
ical investigation of the leaf lamina and petiole of six
genera of Icacinaceae in West Malaysia, Teo & Haron
(1998) reported that these genera can be classified in-
to four closely-knit groups by virtue of their many
shared characters, such as the shape of the vascular
bundles in both midrib and petiole, presence of fun-
nel-shaped palisade cells, foliar sclereids, tannin crys-
tals, a hypodermis layer and accessory or wing bun-
dles in the petiole. They also mentioned that there
is variability in the petiole outline, midrib and stem
anatomy, including vascular bundle arrangement in
the midrib of these species.
Anatomical characters of the stem have been con-
sidered key features for the intrafamily classification
of Icacinaceae (Lens & al. 2008). Lens & al. (2008)
noted that wood structure of the four Icacinoideae
sub families (Icacineae, Iodeae, Sarcostigmateae, and
Phytocreneae) does not offer straightforward characters
to define the family boundaries, because Icacinaceae
s. str. are probably not monophyletic (Kårehed 2001).
Nevertheless, some wood features merit special em-
phasis because of their predictive value to assign a
species to one of the four subfamilies. Also, within
Icacinaceae s. str., the Icacina-group (including the
bulk of the climbing genera plus some non-climbing
ones) is rather homogeneous and can not be easily
distinguished from the other Icacinaceae lineages,
due to a combination of anatomical characters. These
include simple vessel perforations, solitary vessels
plus tangential multiples, a tendency to alternate
vessel pitting, and relatively short vessel elements
and fibers (Kårehed 2001). In another member of
Icacinaceae, Patel and Bowles (1978) reported more
or less evenly distributed vessels, angular, and mostly
solitary, with frequent false tangential pairs, owing
to the overlapping oblique end walls, sometimes in
radial multiples of 2–3, occasionally in tangential
57Phytol. Balcan. 27(1) • Sofia • 2021
pairs. In our study, we have observed mainly solitary
vessels with no visible rays, seldom in radial pairs or
multiples in I. mannii, tangential and radial pairs in I.
oliviformis, and tangential pairs and radial multiples
of 2–6 vessels in I. trichantha.
This study confirms non-occurrence of druses in
I. mannii as reported by Lens & al. (2008), presence of
druses (calcium oxalate crystal) in I. oliviformis only
in the midrib and petiole of this species, and absence
of druses in I. trichantha. Lens & al. (2008) have also
observed the presence of crystals in clusters: raphides
and prismatic crystals. In this study, the authors have
recorded a cluster of crystals in the midrib of I. olivi-
formis. Their finding is in conformity with Metcalfe
and Chalk (1950), who reported absence of druses in
most members of Icacina, and with Lens & al. (2008),
who reported that druses are absent in I. mannii.
Abundance of sclereids differed from species to
species in the studied corm of the species, and thick-
walled sclereids were observed in the roots of I.
trichantha. The Icacina species contained tannins and
starch in varying amounts. These compounds have
different medicinal properties (Ezeigbo 2010; Sarr &
al. 2011, Timothy & Idu 2011; Onakpa & Asuzu 2013;
Okoronkwo & al. 2014; Shagal & al. 2014) and starch is
a major food substance (Fay 1991). Starch in the corms
and tannins in the leaves and stems of the Icacina species
have been confirmed in the diet of different peoples in
Africa (Fay 1991, 1973; Ezeigbo 2010; Sarr & al. 2011;
Timothy & Idu 2011; Onakpa & Asuzu 2013; Shagal &
al. 2014; Okoronkwo & al. 2014).
The existing reports have shown that differences in
the trichome (hair) ontogeny, type, size, shape, abun-
dance, and distribution could be useful in delimiting
the plants of the same family and genus (Levin, 1973;
Payne, 1978; Werker, 2000; Yang and Ye, 2013; Wag-
ner et al., 2004; Ma & al. 2016). These trichomes are
epidermal appendages, unicellular or multicellular,
branched or unbranched, glandular or non-glandular
(Levin, 1973; Werker, 2000; Yang and Ye, 2013). Ma &
al. (2016) have used trichome morphology, structure
and ontogeny, diversity, and distribution to delimit
34 species of Vitis (Vitaceae). The indumentum of
Pyrenacantha consists of simple (unmodified), ‘glob-
ular’ and ‘uncinate’ trichomes, whereas that of Apo-
dytes and Cassinopsis consists of simple hairs. Muci-
lage cells were found only in members of Apodytes.
Intercellular, predominantly wart-like pectic protu-
berances are present in the mesophyll of mature leaf
samples of A. geldenhuysii van Wyk & amp; Potgieter
and Cassinopsis (Potgieter & van Wyk 1999). Simple
non-glandular unicellular hairs and sessile or short-
stalked stellate hairs were observed in the studied spe-
cies, varying from 8.1 µm in I. mannii to 146 µm in I.
oliviformis. I. trichantha could be easily distinguished
from I. mannii because of the presence of short-stalked
stellate hairs and the length of trichomes.
The study on the Icacina species has shown some
morphoanatomical similarities. Midrib vascular bun-
dle arrangement, outline of the petioles, abundance of
hair, percentage of palisade cells, thickness of lamina,
presence or absence of druses in petiole and midrib,
stomatal types, stomatal index, and presence of galls
on the leaves of I. oliviformis are reliable characters for
distinguishing the studied species.
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