European Journal of Advanced Research in Biological and Life Sciences Vol. 5 No. 1, 2017 ISSN 2056-5984
Progressive Academic Publishing, UK Page 36 www.idpublications.org
COMPARATIVE ANATOMICAL STUDY OF SOME ACACIA TAXA
SEEDS GROWN IN CENTRAL SUDAN
Eiman Mohammed Ali Mustafa, Hatil Hashim Alkamali
& Ahlam Salih Eltahir
1Department of Botany, Faculty of Science and Technology
Omdurman Islamic University, Omdurman, SUDAN
ABSTRACT
This study deals with the anatomical characters of eight species and subspecies of Acacia
(Acacia mellifera, A.nilotica ssp. adansonia, A. nilotica ssp. nilotica, A. orefota, A.
polyacantha ssp. cambylacantha, A. Senegal var. Senegal, A. seyal var. seyal, and A.
siberiana var. , siberiana) which were collected from central Sudan. Wax methods were
adopted to make transverse sections in the seeds, the prepared slides were investigated and
compared. It is found that the seeds of the studied plants are more or less similar in their
general internal structure The epidermis is formed of uniseriate cells covered by cuticle,
followed by lignified cells of different thicknesses , they are 6-7 layers in A. mellifera, A.
niloticassp, adansonia, A. nilotica ssp nilotica, and A. sieberiana var sieberiana, and 3-4
layers in A. orefota, A. polycanthas sp campylacantha, A. Senegal var Senegal and A. seyal
var seyal. Many layers of thick walled lignified parenchyma tissue ranging from 3-25 layers.
The embryos formed of two elongated cotyledons the structure of the embryo is different in
A. mellifera, A. niloticassp, adansonia, A. nilotica ssp nilotica and A. seyal var seyal . The
outermost layer of the embryo is formed of one layer of small compact cells surrounding
parenchyma cells filled with reserved food materials their nature and quantities differ from
one species to another.
Keywords: Anatomy , Seeds, Acacia, Seed coat, Embryo.
INTRODUCTION
The genus Acacia is quite abundant diverse comprising approximately 1356 species, which is
currently divided into three subgenus: subg. Acacia (c.161), subg. Acuiferum (c. 235 species)
and subg. Phyllodineae (c. 960 species).
Most species of Acacia tolerate extreme dryness and adopt well to degraded soils, and they
play an important role in the conservation and improvement of soil fertility by means of
nitrogen fixation (Allen and Allen,1981; Karlin et al; 1997). Their wood is hard, heavy, and
digable. Gum Arabic is obtained from some Acacia species (Lean de Pinto et al., 1998), and
Acacia flowers are important for the perfume industry (Allen and Allen,1981). Some species
are grown as ornamental and /or shade trees, while armed shrubs are suitable for fences.
In Sudan Acacia represented by 34 species (AL-Amin,1990). A numerical taxonomy review
on morphology of northern Sudanese Acacia species has been carried out by Kordofani and
Ingrouille (1991). Several studies emphasize seed morphology as an important tool for the
taxonomic work. In spite of the importance and stability of seed characters in systematic,
very little work seems to have been done on seed anatomy of Acacia, especially no studies
have been conducted so far regarding the seeds of Acacia mellifera, A.nilotica ssp.
adansonia, A. nilotica ssp. nilotica, A. orefota, A. polyacantha ssp. cambylacantha, A.
Senegal var. Senegal, A. seyal var. seyal, and A. siberiana var. , siberiana. (AL-Gohary and
European Journal of Advanced Research in Biological and Life Sciences Vol. 5 No. 1, 2017 ISSN 2056-5984
Progressive Academic Publishing, UK Page 37 www.idpublications.org
Mohamed, 2007). Nahed et al 2012 outlined the morphology and anatomy of the seeds of
elven species and sub species of Acacia and constructed an artificial key indicating that these
characters of the seed anatomy contribute in the classification of Acacia species. Little
studies on the seed anatomy of Acacia have been reported. Various seed microscopical
studies of leguminous taxa have been performed from time to time (Sharma et al., 1977; Buth
and Narayan, 1986; Sahai, 1999; Murthy and Sanjappa, 2002, Mallick and Sawhney 2003,
Salimpuvret al 2007, ( E-Khamali and Rehab, 2010).
The aim of this study is to identify and differentiate selected Acacia taxa seeds. In order to
achieve this goal:
The most important characters in the micro morphological differentiation of studied Acacia
taxa (viz ; A. mellifera (Val) Benth, A. nilotica ssp. adansonia, A. nilotica ssp. nilotica,
A.oerfota L., A. Polyacantha Willd ssp. campylacantha (Hochst.exA.Rich.) Brenan, A.
senegal (L.)Willd.var. .senegal Brenan, A. seyal Del. and A. sieberana DC. var A.
sieberiana). Micro morphological characters of studied taxa through anatomical studies by
Light Microscope(LM).
MATERIALS AND METHODS
Plant Materials
Acacia seeds of (8 taxa) : Acacia mellifera, A. nilotica ssp. adansonia, A. nilotica ssp.
nilotica, A. oerfota, A. polycanthas sp. Campylacantha, A. Senegal var senegal, A. seyal
var seyal and A. sieberiana var sieberiana were collected from various areas of West Sudan.
The seeds were identified by plant taxonomist Ustaz Hasan AL-Bager (Soba Research
Forests, Ministry of Science and Technology, Khartoum.). The identification of the studied
taxa was also done according to AL-Amin, 1990. Voucher specimens were kept at Herbarium
of Botany Department, Faculty of Science and Technology Omdurman Islamic University.
Methods
The anatomical investigation was achieved through transverse sections of seed by a hand
microtome and stained with safranine and light green stains (Alexander, 1940).
Preliminary treatment of the plant material
Imbibing
The seeds were soaked in running water not more than 24 hour to avoid germination, seeds
coat were partially by using filter paper.
Fixation
The seeds were sliced befor fixation so as to facilitate the passing of chemical and wax later
on.Transferred seeds into specimen bottle filled with a fixative of (F. A. A.) Formaldehyde:
Acetic acid: Alcohol (5:5:90v/v) fixed for 24 hours.
Washing
The fixed seeds were washed with distilled water threetimes interval.
European Journal of Advanced Research in Biological and Life Sciences Vol. 5 No. 1, 2017 ISSN 2056-5984
Progressive Academic Publishing, UK Page 38 www.idpublications.org
Dehydration
Dehydration by using serial concentrations of ethyl alcohol 70%, 90%, 95% and absolute
alchohol respectively, 24 hour for each step.
Clearing
For clearing the seeds they were transferred every three hours from a mixture of 1:1 cedar
wood oil: absolute alcohol, into pure cedar wood oil followed by mixture of cedar wood oil
and xylene then left over night in pure xylene.trimmed then put the specimen bottle in an
oven adjusted at 60˚C left to half hour, then pure melted wax to half hour, then again pure
wax to half hour.
Blocking
After preparing 9 bath provided with cool water-spatula then took the plant matrrial by the
spatulathen locate it in the wax to give the desired section.after that the plant segments were.
Sectioning
Seeds were sectioned using a Rotatory Microtome (Leitz1512 West Germany), with
Specimen Holder and Disposable Blade Holder. All controls were placed on the front of the
microtome ensuring convenient operation during the setting of section thickness, the
controlling sectioning of the object, and the rapid adjustment of the knife. For precise
alignment of the specimen and the knife, the specimen clamp can be tilted through 10degrees
in any direction by means of two knurled screws.
The microtome adjusted at 7 microns. Using a brush, the ribbons of sections were collected
on glassed slides, which had been wetted with egg albumin to keep the sections attached to
the slides. The slides were left overnight on a hot plate to give maximum expansions of the
seeds.
Staining
Dewaxing of seeds was done by immersing the slides with their sections in pure xylene for 3
minutes. The sections were then dehydrated by transferring then into series of ethyl alcohol
concentration 100% ,95% ,90% 70%, and 50% respectively in 3 minutes for each step and
was stained by flooding them with safranin stain dissolved in 50% ethyl alcohol. They were
then dehydrated back into 50%, 70%, 90%, 95% and 100% respectively in two minutes for
each step and then was stained with safranin stain about two minutes then was stained fast
green stain afew seconds, then washed it in absolute alcohol then xylene washed in mounted
in a drop of D.P.X, and was covered with a cover slip.
Drying
The prepared slides were left to dry in an oven adjusted at 60˚C for at least three days.
European Journal of Advanced Research in Biological and Life Sciences Vol. 5 No. 1, 2017 ISSN 2056-5984
Progressive Academic Publishing, UK Page 39 www.idpublications.org
Microscopical examinations
The prepared permanent slides were examined using (Leitz Dialux20), Microscope with large
field of view at critical sharpness to the very edge of the picture, by more than 23%
compared with conventional microscopes, using power X20, X100 and X400.
Photographing
The prepared slides were photographed using (Olympus VANOX AHBT3), Manual/Semi –
automatic Camera System with Focusing magnifier and Polaroid Camera back with Leitz
0.8X relay lens.
RESULTS AND DISCUSSION
The seeds of studied eight taxa of Acacia species were anatomically investigated. The present
work deals with the following taxa: Acacia mellifera, A. niloticassp, adansonia, A. nilotica
ssp nilotica, A. orefota, A. polycanthas sp campylacantha, A. Senegal var senegal, A. seyal
var seyal and A. sieberiana var sieberiana .
Seed sections were obtained and used to establish tissue and cell features. The internal
structure of the seed is differentiated into two distinct regions , the seed coat and the embryo.
The seed coat
An anatomically complex structure of the seed-coat is a general characterstic of all members
of the Leguminasae. Variations may be useful at the generic level.
The seed coat of Acacia species have a rough cuticle surface and rigid structure. The structure
of the seed coat shows that there are significant differences among taxa based on the layers
and cell sizes of seed coat. The seed coat is formed of:
The epidermis
The outermost layer of the seed coat, it is appeared in small regions in the sections of A.
nilotica ssp. adansonia, A. orefota, A. polycanthas sp campylacantha, and A. seyal var seyal
(plate 1 (2,4,5 and 7)) and it is not appeared in the rest of the studied species it was cut
(plate1( 1,3,6 and 8)). The epidermis is formed of uniseriate cells covered by cuticle. This
layer is called palisade layer it is formed of malphigian cells with an un evenly thickened
walls, and as stated by (Esau,1960), the palisade layer characteristic of leguminous seeds and
its structure in hard legume seeds is connected with their high degree of impermeability and
thus their germinability.
The sub epidermal layer
It followed the epidermis (plates 2-9), it is formed of two regions;
i. Lignified cells of different thicknesses , they are 6-7 layers in A. mellifera, A. niloticassp,
adansonia, A. nilotica ssp nilotica, and A. sieberiana var sieberiana, and 3-4 layers in A.
orefota, A. polycanthas sp campylacantha, A. Senegal var Senegal and A. seyal var seyal .
ii.Many layers of thick walled lignified parenchyma tissue ranging from 3-7 layers in all the
studied species except in the two sub species of A. nilotica where it is very wide (20-25
layers).
European Journal of Advanced Research in Biological and Life Sciences Vol. 5 No. 1, 2017 ISSN 2056-5984
Progressive Academic Publishing, UK Page 40 www.idpublications.org
The endosperm
Is the innermost layer of the seed coat region, it is formed of one layer of small parenchyma
cells in all the species and sub species studied Leguminous seeds are exalbuminous. The
food materials are stored in the cotyledons of the embryo.
The embryo
Dicotyledonous embryos formed of two elongated cotyledons (plates 1) the structure of the
embryo is different in A. mellifera, A. niloticassp, adansonia, A. nilotica ssp nilotica and A.
seyal var seyal but this may be due to different stages of development. The outermost layer
of the embryo is the epidermis and it is formed of one layer of small compact cells
surrounding ground tissue of parenchyma cells filled with reserved food materials their nature
and quantities differ from one species to another (plates 2-9).
1 2
3 4
5 6
7 8
Plate1 Transverse sections of the seeds (X20) of (1) Aacia mellifera,
(2) A. nilotica ssp adansonia, (3) A. nilotica ssp. Nilotica, (4) A. oerfota, (5) A. polyacantha
spp camplyacantha (6) A. Senegal var senegal (7) A. seyal var. seyal, (8) A. sieberiana
var sieberiana
European Journal of Advanced Research in Biological and Life Sciences Vol. 5 No. 1, 2017 ISSN 2056-5984
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Plate2 Aacia mellifera(X 100)
Plate 3 Acacia nilotica ssp. Adansonia (X 100)
Plate 4 Acacia nilotica ssp. Nilotica (X 100)
European Journal of Advanced Research in Biological and Life Sciences Vol. 5 No. 1, 2017 ISSN 2056-5984
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Plate 5 Acacia oerfota(X 400)
Plate 6 Acaciapolyacanthasppcamplyacantha(X400)
Plate 7 Acacia Senegal var Senegal (X100)
European Journal of Advanced Research in Biological and Life Sciences Vol. 5 No. 1, 2017 ISSN 2056-5984
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Plate 8 Acacia seyal var. seyal (X 100)
Plate 9 Acacia sieberiana var sieberiana (X 100)
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