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JOURNAL OF RESEARCH IN NATIONAL DEVELOPMENT VOLUME 6 NO 2, DECEMBER, 2008

MORPHOLOGICAL AND PALYNOLOGICAL OBSERVATIONS IN SOLANUM MELONGENA AND SOLANUM NIGRUM (SOLANACEAE)

C.U. Nwachukwu
Department of Biology, Alvan Ikoku College of Education, Owerri
Nicodemus U. Duru
Department of Biotechnology, Federal University of Technology, Owerri; and
Franca Ezennaya
Department of Plant Science, Imo State University, Owerri

Abstract
Morphological and palynological observations were made on Solanum melongena and Solanum nigrum of the tribe Solaneae and order Solanales from Imo state with aid of light microscope. This is with a view of establishing intra-specific relationship between the two  taxa.The results of the vegetative and floral morphology showed that there exist similarities in the habit, leaf attributes of type,shape,arrangement, attachment,margine,base sepal number and colour, petal number and colour, while differences exits in the colour of the stem, leaf texture, apex and size(length and breadth).The result of the palynology revealed that the species  share common features in the pollen symmetry,shape,aperture and sculpturing(scabrate) while differences exist in the pollen sizes. That of S.melongena having polar dimension(21.2µm),equatorial dimension(19.0µm), pollen form index(1.12µm) and exine thickness(2.15µm)while S. nigrum has polar dimension(20.1µm),equatorial  dimension(18.4µm),pollen form index(1.09µm) and exine thickness (1.65µm).The morphological and palynological results obtained above alongside other taxonomic differences  can be used to enhance proper understanding of the two species in particular and the genus Solanum in general
.
Keywords: Taxonomy, Solanum, Morphology, Palynology, Pollen, Solanaceae.


Introduction
Solanum melongena and Solanum nigrum belong to the family Solanaceae (order Solanales).They are mostly twinners with 90 genera and 2000 species (Willis, 1985). The genus Solanum has about 1,700 species which are widespread in distribution. They are dicotyledonous plants bearing berries with numerous seeds. According to Benson (1957), Solanum species are herbs, Leaves are simple, pinnate and alternate. Flowers are radially or rarely bilaterally symmetrical, with hypogenous discs, sepals are usually coalescent for almost their full length, the calyx is persistent often enlarging in fruits, corolla rotate to tubular,carpels 2,the style 1,the ovary usually 2 chambered or sometimes 3-5 through irregularities of the placenta,plantae axile,ovules numerous in each carpel, fruit berry.

The use of vegetative and floral morphology in the systematic grouping, characteristics and classification of different taxa is no more a new event. For example, Pandey (2000) used morphological features in recognition of two Solanaceae subfamilies of solanoideae and cestroideae.Edeoga et al (2000) used vegetative and floral characteristics to classify some species of Dioscorea.

Similarly, Mbagwu and Edeoga (2006) did similar work in 8 Vigna species. Further more, Nwachukwu and Okeke (2001) used morphological characters in the characterization of Maesobotrya, barteri var bateri. Equally important is the pollen morphology. Study of pollen grains has been very helpful in assigning the status of plant since pollen grain wall has specific characters.


Journal of Research in National Development 6(2) December, 2008


An excellent review of the systematic application of palynology is given by Erdtman (1952) and good examples of the use of pollen in systematic studies are given by Agwu and Beug (1982), Cowan (1969) in genus Swartzia, Edeoga et al (1996).

 Economically members are used in the production of drugs e.g. pharmaceutical steroids. The leaf juice is used in treating inflammation of the kidney and bladder and in gonorrhoea, dropsy, heart diseases. Bile and enlargement of the spleen, Pandey (2000).Pollen grains on the other hand have been used by forensic experts in criminal cases.

Despite the numerous economic and agronomic importance of the Solanum species, there is absence of clear taxonomic criteria especially in the morphology and palynology to delineate these taxa. Hence, the objective of this study is to provide detailed morphological and palynological information on the two Solanum species for accurate description and proper identification of the species.

Materials and Methods
Morphological studies were made on fresh samples of S.melongena and S.nigrum.The

collections was made from different locations in both Imo and Anambra states such as Egbeada, Okigwe, Akokwa, Umuchu and Achina.The length and width of the leaves were measured using a 30cm meter rule. This was done by spreading the middle leaflet on a flat surface of a laboratory bench. For the width, the same median leaflet was chosen to avoid being biased.

For the pollen study, pollen grains from each species were collected by tearing out fresh and mature flowers of these floral on a slide. Samples were made on fresh flower from September to October 2007 at the science laboratory of University of Nigeria, Nsukka.Samples for the light microscope were acetolysed following slight modifications (Erdtman, 1996).Unstained, acetolysed pollen grains were mounted on slides and covered with a zero size cover slip, sealed with nail polish. The photomicrographs of pollen grains were taken from the slides using a LEITZ WETZIAR ORTHOLUX microscope fitted with a vivitar-V335 camera.

Results
The results of the morphological study of the two Solanum species are tabulated below in table 1 a


 

Table 1 a: Vegetative Morphology of S. melongena and S.nigrum.


CHARACTERS                           S.melongena                                 S.nigrum

Habit
Height
Stem
Type
Colour
Leaf
Texture
Arrangement
Attachment
Type
Shape
Margin
Venation
Apex
Base
Length
Breadth

Herb                
90-150cm

Erect and much branched
Light green/grey

Hairy
Alternate
Axillary
Simple
Ovate
Undulate
Reticulate
Long acuminate
Obtuse
7-14.5cm
4.5-5.5cm

Herb
70-120cm

Erect
Green

Smooth
Alternate
Axillary
Simple
Ovate
Undulate
Reticulate
Shortly acuminate
Obtuse
2.5-7cm
2.4-5.0cm

 

 

Table 1 b: Floral Morphology of the two Solanum species studied

cvcccvzcvcxccvcvCHARACTERS                       S.melongena                                             S.nigrum                                                       
 
INFLORESCENCE
Type                                         Short cyme                                                Extended cyme                
Floral symmetry                       Actinomorphic                                                Actinomorphic 
SEPAL
Number                                      5                                                                         5
Colour                                        green                                                                green
Freedom/Fusion                       fusion                                                                 fusion
PETALS
Number                                     5                                                                  5
Colour                                       White                                                          White
Freedom/Fusion                      Fusion                                                          Fusion  

ccvcvc

 

PICTURE                                                                 (a)                                                                                                        PICTURE 1                                                                                         (b)                                                                     Fig. 1:             Morphology of (a) S. melongena (b) S. nigrum
                                                                                               

 

    PIC 1      PIC 2                                                         (a)                                                                   (b)
Fig.2: Pollen grain of two Solanum species (a) showing thick exine wall of 2.15µm and (b) showing thick exine wall of 1.65µm


The results of the vegetative features of the two species studied showed that the species share certain morphological characteristics in common. These include habit (herb), leaf type, shape (ovate), margin, venation, leaf base (obtuse) e.t.c .Table 1 a, 1 b, fig. 1 and 2. In contrast, the stem bark of S. melongena is grey while that of S.nigrum is green in colour. The texture of S.melongena is hairy while that of S.nigrum is smooth. The leaf apex of S.melongena is long acuminate with broad leaves while that of S. nigrum is short acuminate with small leaves.
The floral morphology (Table 1 b) showed that the species studied share almost the same feature in common except for the inflorescence type which shows its short cyme in S.melongena and extended cyme in S.nigrum.The important characters of the pollen grains of the two species of Solanum studied are summarised in table 2


xXcXXcXcXcxcTable 2: Palynomorphological features of two Solanum species studied.
ccATTRIBUTES                                                
S.melongena                                                    S.nigrum
Wall Sculpture                                     scabrate                                   scabrate
Aperture                                              Tricolporate                             Tricolporate
General appearance of pollen  Subspheroidal              Subspheroidal
Symmetry                                            Grain polar & radially  Grain polar & radially symmetrical symmetrical
Polar view shape                                  Quinquangular             Quinquangular
Equatorial view shape                          Elliptic                                     Elliptic
Exine thickness                                    2.15µm                                    1.65µm
XcX 



 

The pollen grains of the two Solanum species studied showed similarities in their pollen attributes of wall sculpture, aperture, and symmetry e.t.c. Table .2 However, the greatest variation observed in pollen morphology of the Solanum species lies in the size of their pollen wall. The greatest thickness of the exine (2.15µm) was observed in S.melongena while 1.65µm was recorded in S.nigrum.This observation reported for the first time could be of taxonomical importance.

Discussion
The results of the morphological features of Solanum melongena and Solanum nigrum studied show some specific characteristics that can be used for taxonomic decision. The variation in height, branching, leaf texture, apex and fruits (Table 1 a, 1 b and 1.2) of the

species studied constitutes an important distinguishing factor that could be used for establishing intraspecific relationship. Solanum melongena grows up to the height of 90-150cm while that of Solanum nigrum range between 70-120cm.S.melongena is much branched and hairy when compared to that of S.nigrum which is less branched and smooth. The leaf apex of S.melongena is long acuminate with bigger fruits unlike that of S.nigrum that is short acuminate with small fruits. This confirms the works of earlier research findings of Benson, 1957; Schipper, 1996; Mbagwu and Edeoga, 2006; Nwachukwu and Mbagwu, 2006; who used morphological variations in taxonomic characterization of plants.

Despite their numerous differences, the two species show similarities in some respects such as habit, leaf type, arrangement, floral symmetry, sepal and petal numbers e.t.c .as shown in Table 1 a, this is in line with the work of Nwachukwu and Edeoga who used floral similarities in the genus Indigofera in establishing intraspecific relationship among species. Similarly, the pollen morphology of the two species of Solanum studied showed slight variations. It was observed that the pollen grain of S.nigrum is small in size (1.65µm) when compared with that of S.melongena (2.15µm).This variation in size may be due to indiscriminate mating leading to hybridization which may be operating in this complex. This is not surprising since previous workers have made similar observations in other groups of angiosperm (Bonnefille and Riollet, 1980; Moore and Webb, 1978; Agwu and Osibe, 1992; Anozie, 1985; Agwu and Beug, 1982).

The pollen shape expressed as the ratio of the length of polar axis to that of equatorial dimension (Erdtman, 1952), is found to be more or less quinquangular in polar view and elliptic in equatorial view in both species. Further more, similarities are found in aperture type (tricolporate), pollen shape (sub spherical) and wall struchcture (scabrate) of the pollen grain of the two Solanum species studied.

The results of the morphology and palynology of the two species of Solanum studied have proved to be of immense assistance in interpreting problems related to plant classification. The results could therefore be utilized with information from other discipline in clarifying taxonomic relationships of these taxa with other genera, species or subspecies.

 

Reference
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Agwu, C.O.C. and Osibe, E.E. (1992): Air borne Palynomorphs of Nsukka during the months of February- April (1990). Nigerian Journal of Botany, 5:117-185

Anozie, G.A. (1985): Pollen analysis of water and sediments from Lake Nguru, Nsukka.B.Sc Thesis.           University of Nigeria, Nsukka.pp .29

Bonnefille, R. And Riollet, G. (1980): Pollen des savannes de Afrique Orientale.Edition du CNRS.Paris

Benson. L. (1957): Plant classification. Lexington: D.C Heath and Company.pp.221-226

Cowan, R.S. (1969): Harleyodendron, a new genus of Leguminosae (swartzieae).Brittonia.31:72-78
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Erdtman, G. (1952): Pollen morphology and Plant taxonomy of Angiosperm.Walthan Mass Herfner             Press.p.515

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