|Reseach Article (Open access)|
Int. J. Life. Sci. Scienti. Res., 4(6): 2116-2121, November 2018
Karyomorphological Studies in Three Species of Alocasia (Schott.) G.Don.- An Ethno-medicinally and Economically Important Genus
Bandana Nabis Das*
Associate Professor, Department of Botany, Handique Girls’ College, Guwahati, Assam, India
*Address for Correspondence: Dr. Bandana Nabis Das, Associate Professor, Department of Botany, Handique Girls’ college, Guwahati, Assam, India
ABSTRACT- Karyomorphological studies in Alocasia macrorrhiza (L.) G.Don., Alocasia fornicate (Roxb.) Schott, Alocasia longiloba Miq. belonging to the family Araceae using root tip squash technique was carried out. It was observed that the chromosome number for the three species was found to be 2n=28 and chromosomes are smaller in size. The chromosomes in Alocasia longiloba were found to be longer in length in comparison to Alocasia macrorrhiza, Alocasia fornicata. Present studies also reveal that the karyotype is a symmetric type. The present karyomorphological study has been undertaken as it is an established fact that karyomorphological analysis forms a prerequisite for the genetic improvement of any plant species. This study would be helpful in the protection, conservations of the species by establishment of germplasm bank.
KEY WORDS- Alocasia macrorrhiza, Karyomorphology, Karyotypes, Symmetric type, Chromosome
INTRODUCTION- The genus Alocasia (Schott) G. Don belongs to the family Araceae consisting of about 2,500 species . There are 79 species native to tropical and sub-tropical Asia to Eastern Australia and wildly cultivated elsewhere . The species of this genus have been distributed in the Northeast and South India, Sri Lanka, and Bangladesh . These are generally grown in marshy lands, but sometimes also in shady damp places in the forest and in village thickets. In this study, three species of Alocasia (Schott) G.Don, A. macrorrhiza (L.) G.Don, A. fornicate (Roxb.) Schott, A. longiloba Miq. were selected. These species are ethno-medicinally and economically important plants. According to IUCN Red list- Alocasia atropurpurea and Alocasia sanderiana are tagged as Critically Endangered .
Several medicinal applications of Alocasia have been reported for South-East Asia. Boiled stems of A. macrorrhizos are used as a laxative, chopped-up roots and leaves as a rubefacient, and juice from the petiole against a cough. The plants are applied for stimulating the skin, e.g. in cases of fever and to remove blotches. The rhizome is sometimes used as a poultice to treat furuncles. The pounded stems are applied as a paste to snakebites and scorpion stings. Alocasia fornicata (Roxb.) Schott is important as food and ethno-medicine in Asia and Africa since time immemorial. In India, many people have been using rhizome paste to treat wounds, cure heel cracks and kill worms in domestic animals. A number of chemicals could be isolated from this species. The antioxidant properties of the edible parts of different plants have already been established . There is growing industrial interest towards the production of herbal antioxidants that can be supplemented in medicine, cosmetics, and nutraceuticals in the modern world.
The tissues of Alocasia contain calcium oxalate crystals, which produce irritation of the skin and inflammations of the oral cavity and mucous membranes. Sapotoxin is also present, and the toxic effects include gastroenteritis and paralysis of the nerve centres. Hydrocyanic acid is often present. The poisonous substances can be removed by repeated cooking, but the rhizomes and bases of petioles of A. macrorrhizos which are sometimes used for food usually contain few poisonous substances. A lectin has been isolated from the rhizome of A. macrorrhizos, which showed potent mitogenic activity on human peripheral blood lymphocytes in the [3H]-thymidine uptake assay. It was a T-cell mitogen and did not induce any appreciable DNA synthesis in B-enriched lymphocytes. This species also contains a protein which inhibits both the enzymes trypsin and chymotrypsin. The seed extract showed antifungal activity. There is also a report on HIV-1 protease inhibitory activity .
Alocasia is a plant of great economic value. Experimentally antimicrobial, antifungal, antioxidant, hepatoprotective, anti-diarrheal, anti-protozoal, anticancer properties have been found in many species of Alocasia. As such it needs conservation and detailed chromosome studies would aid in creating germplasm .
Hence, the present study has been undertaken:
To conduct karyomorphological studies in three species of Alocasia (Schott) G.Don:
o Alocasia macrorrhizos (L.) G.Don
o Alocasia fornicate (Roxb.) Schott
o Alocasia longiloba Miq.
MATERIALS AND METHODS
In the present investigation three species of Alocasia (Schott) G.Don were collected from different localities of Greater Guwahati. The saplings were potted inside the institute campus for collection of fresh roots for the experiment. The following investigation proceeded for 5 months i.e. from January to May 2017.
Cytological investigation- For chromosome characterization in A. macrorrhiza, A. fornicata and A. longiloba detailed karyotypic studies were undertaken. Karyotypes were prepared from the somatic chromosomes. For cytological studies, root tips squash technique is done. Very young root tips were collected from the plant between 7:45 AM - 8:15 AM washed in double distilled water and pre-treated with saturated solution of Para dichlorobenzene at a suitable temperature for 3 hours at 4°C ± 2°C. Pretreated young root tips are fixed in a suitable fixative such as Carnoy’s fluid- 2(1:3:6; Glacial acetic acid: Chloroform: Ethanol) for 24 to 28 hours at room temperature. After fixation the root tips were thoroughly washed with 70% ethanol and finally they were stored used for cytological work. For the preparation of slides the root tips were first hydrolysed with 1N HCl and stained with aceto orecin and warmed over flame for 10 to 15 minutes and kept for 2 - 3 hours at room temperature. Single root tip was taken in a drop of 45% acetic acid on a slide. Only the dividing tip region was taken discarding the other tissue. Cover slip was placed over the tip and squashed by applying uniform pressure with the thumb through a piece of blotting paper, a gentle tapping followed by heat fixing and finally sealed with paraffin for further studies [8,9].
The temporary slides thus prepared were observed under compound microscope at a magnification of 1000x using oil immersion (10×100x, oil immersion). This procedure was standardized through trial and error method. Metaphase plates were selected for karyomorphological analysis of the chromosomes. Perfectly stained chromosomes were photographed using Trinocular microscope-N400-M, CMOS camera 5M with image analysis system. The drawings of the chromosomes were made with the help of camera lucida apparatus. Idiograms were then constructed on tracing paper.
Following parameters of the chromosomes were considered:
i) Length of the long arm
ii) Length of the short arm
iii) Total length of the chromosome
iv) Volume of the chromosome
v) Relative length
vi) Centromeric position
On the basis of the length, the chromosomes lengths were categorized under the following types-
Type A= 3.00 µm and above
Type B= 2.50 µm - 2.90 µm
Type C= 2.00 µm - 2.49 µm
Type D= 1.00 µm - 1.90 µm
Type E= 0.01 µm - 0.99 µm
The volume of an individual chromosome was calculated as chromosome volume (V) = πr2h.
Where, r =radius of the chromosome; h=length of the whole chromosome. The total chromosome volume was then expressed by adding the volumes of all the chromosomes. On the basis of centromere position, the chromosomes were classified into metacentric, sub-metacentric, sub-telocentric, and telocentric following the nomenclature system of Levan et al. .
Fig. 1 (a-d): Karyotype and Ideogram of somatic chromosomes of Alocasia macrorrhiza (L) G.Don