(Acanthaceae) from South India

Transcription

1 _??_ 1990 by Cytologia, Tokyo Cytologia 55: , 1990 Karyotypic Studies in a Few Species of Barleria L. (Acanthaceae) from South India Accepted December 12, 1988 R. M. Ranganath and D. G. Krishnappa Department of Botany, Bangalore University, Jnana bharathi, Bangalore , India Species of Barleria L. numbering about 230 (Airy Shaw 1973) show a wide range of mor phological variations. Some of them are of horticultural interest for their attractive flowers. Nineteen species are known to occur in South India (Gamble 1935). Cytological work in the genus, as in most other members of Acanthaceae, is very little. Though De (1966) and Datta and Maiti (1970) have described karyotypes for a few taxa from North India, those occurring in South India have not received due attention so far. The present work, however, unravels karyotypes in six species distributed in South India and discusses their relationship based on chromosome morphology. Materials and methods Places of collection of the taxa examined are shown in Table 1. The herbarium specimens are deposited in the Department of Botany, Bangalore University, Bangalore. Excised root tips were pretreated with 0.2 M solution of 8-hydroxyquinoline for a period of 2-3 hours at Ž and processed according to Feulgen schedule. Meiotic studies were made by smearing anthers in 2 percent Propionocarmine stain. Camera lucida drawings and photomicrographs were obtained from semi-permanent slides. Chromosomes were classified based on their length; Type A=long (more than 4ƒÊm), Type B=medium-sized (4ƒÊm-2.5ƒÊm), Type C=short (1ƒÊm-2.5ƒÊm) and Type D=very short (less than 1ƒÊm). The superscript m, sm, st are given to denote the median, submedian, subterminal position of the centromere and ss and sl to denote the satellites on short arms and long arms in the respective types. Results and discussion The details of karyotypes of the taxa examined are summarised in Table I and Figs. 1 to 6. Idiograms are represented in Fig. 7. A perusal of the available literature shows that the lowest number recorded in the genus is 2n=30, while the highest is 2n=42. De (1966) based on the reports of Narayanan (1951) suggested that all the known numbers in the genus are derived from alterations of the basic number of x=15. However, 2n=40 is found inmost of the species of Barleria studied so far (Table 2). It is, however, premature at present to draw a definite conclusion on the basic number of the genus when the cytological information available is meagre. Besides, some of the earlier counts need to be confirmed employing recent techniques. The presence of 2n=32, 34, 36, 38, 40 and 42 indifferent horticultural varieties of B. cristata may be attributed to aneuploid alterations and hybridization resulting in a complex. The karyotypes of B. acuminata, B. buxifolia, B. gibsoni, B. involucrata var. elata and B. noctiflora described here are new reports. The South Indian population of B. strigosa with its

2 176 R. M. Ranganath and D. G. Krishnappa Cytologia 55 Figs Photomicrographs of somatic metaphase chromosomes. 1, B. involucrata var. elata (2n=40). 2, B. buxifolia (2n=40). 3, B. noctiflora (2n=40). 4, B. acumillata (2n=40). 5, B. gibsoni (2n=40). 6, B. strigosa (2n=40).

3 1990 Karyotypic Studies in a Few Species of Barleria L. 177 new number of 2n=40 is also different from the earlier account by De (1966). All the species studied here have revealed the same chromosome number of 2n=40. The karyotypes, in general, are symmetrical with most of the chromosomes showing more or less equal arms. However, each taxon studied here is distinct in respect of the relative positions of the centromere, length of the individual chromosomes and the total length of haploid set. Table 1. Collection localities, karyotype formulae and total chromatin length of haploid set of the taxa studied Fig. 7. Idiograms of the species of Barleria L. studied. Thus, B. involucrata var. elata shows the longest chromosomes of all the species studied here (upto 7ƒÊm.). The presence of a pair of heteromorphic chromosomes is also distinct. On the other hand, B. acuminata possesses shortest chromosomes (1.73ƒÊm) with three pairs of them bearing satellites on their short arms.

4 178 R. M. Ranganath and D. G. Krishnappa Cytologia 54 Among the other four species, B. noctiflora possessing long and medium-sized chromo somes has 2 pairs of satellited chromosomes. B. gibsoni with medium-sized and short chro mosomes has a single pair of satellited chromosomes. B. buxifolia lacks satellited chro mosomes and is thus different from others. Similarly, B. strigosa is distinct with 3 pairs of satellited chromosomes, of which 2 pairs are on short arms of sub-metacentric pairs, while the third pair of satellites is on relatively longer arms of a nearly metacentric pair. Table 2. Chromosome counts known in Barleria L. along with corresponding author(s) and year(s) of publication The karyotype of B. strigosa is also known from the work of De (1966) for a population occurring in North India. The author has reported 2n=42 which is at variance with the present findings of 2n=40. Though De (1966) has recorded 3 pairs of satellites, none of them are on long arms as seen in the population studied here. Apart from the above, the taxa B. buxifolia, B. noctiflora, B. involucrata var. elata, B. strigosa and B. gibsoni are with 2, 4, 6, 8 and 14 chromosomes bearing sub-terminal centromeres, respectively. Of these, B. gibsoni with 14 acrocentric chromosomes may be treated to have a

5 1990 Karyotypic Studies in a Few Species of Barleria L. 179 highly evolved karyotype, whereas the karyotype of B. acuminata without acrocentric chromo somes in its complement appears to be least evolved. The presence of relatively long chromosomes and a relatively high basic number of x= 20 makes Barleria a distinct taxon among Acanthaceae. De (1966) has even suggested its re moval from the sub-family Justiceae on these grounds. But, paucity of sufficient cytological data in the members of Acanthaceae makes it difficult to examine this aspect judiciously, at present. Summary Karyotypes of six species of Barleria L. occurring in South India viz., B. acuminata, B. buxifolia, B. gibsoni, B. involucrata var. elata, B. noctfora and B. strigosa are studied. All the six species have the same chromosome number of 2n=40. However, each species is distinct in respect of relative positions of centromere, presence/absence and position of satellites and total haploid chromatin length. The diagnostic value of the karyomorphological details in these taxa is discussed. References Airy Shaw, H. K A dictionary of flowering plants and ferns. Ed. J. C. Willis. Cambridge Univ. Press. Datta, P. C. and Maiti, R. K Relationships of Justiceae (Acanthaceae) based on cytology. Genetica 41 (3): De, A Cyto- and histogenetical studies in the family Acanthaceae. Report Bose Inst.: Cytological, anatomical and palynological situdies as an aid in tracing the affinity and phylogeny in the family Acanthaceae I. Cytological studies. Trans. Bose Res. Inst. 29: Ellis, J. L Chromosome number in some members of Acanthaceae. Science and Culture 28: Gamble, J. S The Flora of Presidency of Madras. Vol. II. B.S.I., Calcutta. Grant, W. F A Cytogenetic study in the Acanthaceae. Brittonia 8: Hooker, J. D Flora of British India. Vol. IV. Krishnappa, D. G. and Ranganath, R. M IOPB chromosome number reports. Taxon 31: Krishnaswami, S. and Madhava Menon Cytomorphological study on some species and interspecific hybrid of Barleria L. Cytologia 39: Mehra, P. N. and Vasudevan, K. N IOPB chromosome number reports. Taxon 21: Narayanan, K. N Somatic chromosomes in Acanthaceae. J. Mad. Uni. 21(B): 232. Pal, M Chromosome numbers in some Indian angiosperms 1. Proc. Ind. Acad. Sci. 60(B): Raman, V. C. and Kesavan, P. C Cytological investigations in some cultivated and wild species of Barleria. J. Bot. Soc. 43: Saggoo, M. I. S. and Bir, S. S Meiotic studies in certain members of family Acanthaceae from South India. J. Ind. Bot. Soc. 65: Verma, S. C. and Dhillon, S. S IOPB chromosome number reports.. Taxon 16: