1971 341 Polyploidy in Trema (Ulmaceae) A. S. Hans1,2,3 Panjab University, Botany Department, Chandigarh 14, India ReceivedDecember 18, 1969 Introduction Trema Lour. belongs to Ulmaceae, a small family of trees and shrubs, encompassing 15 genera and about 150 species (Lawrence 1951) in tropics and subtropics of both the hemispheres. Trema is a small genus composed of 30 tropical species of which only three species constitute the Indian flora. The members of the Ulmaceae show variation in basic chromosome number. Celtis is polybasic with x=10, 11, and 14 (Darlington and Wylie 1955), while Ulmus, Holoptelea and Zelkovia exhibit a uniform base number of 14. A few instances of inter and intraspecific polyploidy in Celtis and Ulmus exist in nature. Celtis australias has been reported to be a tetraploid (2n=40), while C. laevigata, C. sinensis, and C. occidentalis are diploid, all with 2n=20 (Bowden 1945). The report of 2n=28 in C. occidentalis (Sax 1933) is suggestive of aneuploid races in the species. Most of the species of Ulmus are diploid except U. americana where in addition to the diploid race (Krause 1930), a tetraploid race is also known (Sax 1933). Artificial triploids and tetraploids have been raised in U. glabra by Ehrenberg (1945). The two chromosomally known species of Trema exhibit variable numbers. T. orientalis has been reported to have n=18 (Arora 1960) from Banglore and n=20 (Gajapathy 1961) from Madras in South India; T. politoria has n=10+B (Mehra and Gill). In view of the discordant reports on the chromosome number (n=18, 20) in Trema orientalis, the cytological study was undertaken to ratify the chromosome number, to assess the incidence of polyploidy, and if possible to determine the base number of this small genus. Material and methods Extensive collections of the material were made during 1965 from the wild populations in Eastern Himalayas growing in nearby areas of Digboi, Shillong, and Darjeeling whose locations along with altitude are given in Table 1. 1 Present address: Tree ImprovementReseach Centre, P. O. Box 1210,Kitwe (Zambia). 2 These studies were part of a bigger project which was financedby the U. S. Govern ment from PL 480 funds in India (Grant A7-FS-12). 3 thank Professor P. N. Mehra for his suggestions during the completion of this work. 23* 342 A. S. Hans Cytologia 36 Table 1. Area of collection Flower buds, for cytological analysis, were fi xed in Carnoy's fluid and after 24 hours trans. ferred to 95% ethyl alco hol. The anthers were subsequently squashed in 1% acetocarmine, and slides were made perma nent in Euparal. Stomatal study was made after keeping the required material in 5.0% KOH solution in the bath at 60•Ž for 3 days. Pollen fertility was determined from the ability of the Fig. 1. Flowering branches of two cytotypes of Trema pollen to stain with amboinensis. A, diploid. B, 16-ploid. glycerocarmine. The voucher specimens have been deposited in the Herbarium, Panjab University, Botany Department, Chandigarh (India). Observations Trema orientalis B1. A small tree, up to 5m in height, with thin, greenish-grey, lenticelled bark. Distributed in sub-Himalayan region from Jamuna eastwards and also in Central, Western, and Southern India. Cytological observations revealed n=10 (Fig. 2) and normal meiosis leading to 100% fertile pollen formation. T. amboinensis B1. A fast-growing tree, having whitish bark with rough warts, and horizontal wrinkles. Most common in hot valleys of Sikkim, Terai, West Duars, Assam, Burma, and Andaman Islands. Chromosomal investigations showed two cytotypes with different levels of 1971 Polyploidy in Trema (Ulmaceae) 343 ploidy. Morphological characters of these are compared in Table 2 (Fig. 1). Discussion Extensive collections in the area of investigation revealed Trema orientalis to have n=10, which differed from the results of n=18 (Arora 1960) and n=20 (Gajapathy 1961) in the plants investigated from South India. Obviously two cytotypes, diploid in North India and tetraploid in South India, do exist. Polyploidy could have played a role in the extension of distributional range to South India. Morpho logical compari son of North and South Indian forms should reveal the extent of differentiation in the taxon. The com parison of the two cytotypes in T. amboinensis showed that 16 - ploid race was larger, had stouter terminal and side bran ches; longer and large stipules, leaves, and stomata; inflo rescence in denser cymes and bigger pollen grains than those in Fig. 2. Trema orientalis, diakinesis, n=10, •~1,600. Figs. 3-8. Trema the diploid race. amboinensis, meiotic chromosomes (•~1,600), stomata (•~880) and pollen (•~440). 3, diploid race, diakinesis, n=10. 4, 16-ploid race, This seemed to metaphase I, n=80. 5-6, stomata of diploid and 16-ploid race respec be indicative of tively. 7-8, pollen grains of diploid and 16-ploid race respectively. 344 A. S. Hans Cytologia36 ' gigantic effect' usually associated with polyploidy. The bivalent pairing and the course of meiosis was perfectly normal in the 16-ploid race, which there. fore, could be an allopolyploid. The fact that the 'hairiness' of the ovary (glabrous in diploid race) is a new character incorporated, also lends support to the allopolyploid constitution of the 16-ploid race. Table 2. Cytotypes of Trema amboinensis Hooker (1885) mentioned T. amboinensis to be "A tree with the habit of T. orientalis from which it differs in the tomentose leaves, and of which it is perhaps a large form as considered by Kurz". The reports of n=10, 18, and 20 in T. orientalis and n=70, and 80 in T. amboinensis show the extent of chromosomal variability in the two species. Also the morphological characteristics of these merge in each other, sometimes making the taxonomic task cumbersome. The Indian species of this genus yielded interesting results, so detailed study, especially, from cytomorphological angle of other species of the world, appears warranted. The present studies revealed that the so far lowest haploid chromosome number reported was n=10 in T. orientalis, T. amboinensis, and also in T. politoria (Mehra and Gill 1968) and could be presumed as its base number. The predominant base numbers in Ulmaceae are 10 and 14. Cytological data support the taxonomical grouping of Trema with Celtis (x=10) in the tribe Celtideae of Ulmaceae. Summary Cytomorphological studies of two species of Trema of family Ulmaceae revealed that T. orientalis with n=10 differed from the previous reports of 1971 Polyploidy in Trema (Ulmaceae) 345 n=18 and 20. In T. amboinensis, two cytotypes, one diploid (n=10) and the other 16-ploid (n=80) have been detected. The morphological differences possibly resulting from polyploidy have been brought out. The base number of the genus is suggested to be x=10. Literature cited Arora, C. M. 1960. New chromosome report I. Bull. Bot. Surv. India 2: 305. Bowden, W. M. 1945. A list of chromosomenumbers in higher plants II. Menispermaceae to Verbenaceae. Amer. Jour. Bot. 32: 191-201. Darlington, C. D. and Wylie, A. P. 1955. ChromosomeAtlas of Flowering Plants. George Allen and Unwin Ltd., London. Ehrenberg, L. 1945. Kromosomalenhos nagra Karlvaxter. Bot. Notiser 1945:430-437. Gajapathy, C. 1961. Cytological studies in some Indian medicinalplants. Bull. Bot. Surv. India 3: 49-51. Hooker, J. D. 1885. Flora of British India. Vol. V. L. Reeve and Co., London. Krause, O. 1930. Cytologische Studien bei den Urticales. Ber. deutsche. bot. Ges. 48: 9-13. Lawrence, G. H. M. 1951. Taxonomy of Vascular Plants. MacMillanCo., New York. Mehra, P. N. and Gill, B. S. 1968. In IOPB chromosomenumber report. Taxon 17: 574 -576. Sax, K. 1933. Chromosomenumbers in Ulmus and related genera. Jour. ArnoldArb. 14: 82-84..