CYTOLOGICAL STUDIES IN THE FAMILY ZINGIBERACE2E WITH SPECIAL REFERENCE TO CHROMOSOME NUMBER AND CYTO-TAXONOMY BY PROF. T. S. RAGHAVAN, M.A., PH.D. (LOND.) AND K. R. VENKATASUBBAN, M.Sc., PH.D. (Annamalai University) Received March 30, 1943 L Introduction THE family Zingiberace~e, according to Willis (1931), contains 45 genera and about 800 species. A few like Globba, Amomum, Alpinia, Curcuma, Costus and Elettaria, have come in for some investigation at the hands of the morphologists, especially in respect of the nature of the labellum. However, cytological information that is available is very meagre. The chromosome numbers known so far in this family are confined only to 11 species spread over 7 genera, a s per fist given below. This paucity of information on the cytology of this family has also been pointed out by Tischler (1937). It was mainly with a view to fill up' the great gaps in our knowledge of the chromo- some numbers' of some of the families referred to by Tischler, that the present investigation was taken up. Attention has been paid mainly to the chromosome numbers, while other cytological details, like chromosome morphology and nucleolar behaviour have been described only in a few cases. A brief discussion regarding the course of evolution in this family, with the data on hand, has also been attempted. GENUS AND SPECIES CHROMOSOME NUMBERS 2n Author year 1. Curcuma longa Linn ..... 64 Sugiura 1936 2. Zingiber officinale Rosc. .. 22 1928 Zingiber officinale Rosc. .. 24 Takahashi 1930 3. Zingiber Mioga Rosc. .. 55 ? Morinaga et al. 1929 4. Phteomeria atropurpurea 24 Boehm 1931 5. Costus cylindricus .. 8 ,, 1931 6. Costus malarotiensis .. 18 Gregory 1936 7. Costus speciosus .. 18 36 Bane~ee 1940 8. Elettaria Cardamomum Maton. 24 48 Gregory 1936 9. Hedychium Elwesi Baker 66 ,, 1936 10. Alpinia calcarata Rosc... 48 Raghavan and 1941 Venkatasubban 118 Cyfological Sludies in the Family Ziugiberace~ 119 IL Materials and Methods Materials for the present study were obtained from the Royal Botanic Gardens, Sibpur, Government Garden, Bangalore and Soundarya Nursery, Madras. Costus speciosus was collected from Tenmalai forests. We are indebted to Dr. S. K. Mukerjee of the Royal Botanic Garden, Sibpur, for help in the matter of identification. In the pre3ent investigation, chromo- some numbers have been determined, most of them for the first time, from somatic metaphase plates. Root tips were fixed in Navashin's fluid for a period of 24 hours. After the usual process of washing, dehydration and infiltration, sections were cut at a thickness ranging from 14-18 microns and stained in Newton's Iodine-Genetian-Violet. The following are the numbers determined in the present study :-- 2n 2n 1. Zingiber officinale Rosc. .. 22 14. Alpinia galanga Sw. obs... 48 2. Zingiber cassumunar .. 22 15. Alphffa nutans Rosc. .. 48 3. Zingiber zerumbet Sm. .. 22 16. Alpinia vittata Bull. .. 48 4. Curcuma aromatica Salisb. 42 17. Alpinia allughas Rose. .. 48 5. Curcuma longa Linn. 62 18. Globba bulbifera .. 48 6. Curcuma amada Roxb. 42 19. Hedychiumflavescens Cau. 34 7. Kcempferia Gibsoni 24 20. Hedychium Greenii .. 36 8. Kcempferia Gilbertii Bull. 36 22. Hedychiumflavum Roxb... 52 9. Kcempferia rotunda Linn. 54 23. Hedychium coronarium 10. Kcempferia Galanga Linn. 54 Koenig. .. 54 11. Costus igneus N.E.Br. 18 24. Hedychium Gardnerianum 12. Costus discolor 18 Rose. .. 54 13. Costus speciosus Smith. 36 25. Hedyehium gracile Roxb... 66 IIL Observations The nature of the chromosomes with reference to their morphology, could not be studied for all the species investigated, on account of their small size and comparatively large number. However, an analysis of the chromosome complements has been made for two species of Costus (C. igneus and C. discolor) and three species of Zingiber, namely, Z. officinale, Z. cassumunar and Z. zerumbet. The chromosome number for Costus igl~eus is 2n = 18 (Text-Fig. 1). Among the chromosomes, there is not much disparity of size. Almost all of them show a median attachment constriction, except the pairs AA and BB which show a subterminal constriction (Text-Fig. 2). Out of the 9 pairs, 6 are rod-shaped while the remaining are crescent-~haped. 120 T.S. Raghavan and K. R. Venkatasubban Costus discolor reveals the presence of 2n = 18 chromosomes (Text- Fig. 3), as in C. igneus. Here also, there is a preponderance of the rod-shaped chromosomes over the crescent-shaped ones. There are 6 pairs of rods and 3 pairs of crescent-shaped chromosomes as in C. igneus. Of the 6 pairs of rod-shaped chromosomes, one pair alone (A'A', Text-Fig. 4), shows the presence of subterminal constriction. It may be mentioned that this pair A'A' is the smallest of the lot. The rest of the chromosomes, both rods and crescents, exhibit median or submedian attachment constriction. The chromosome morphology in the two species described above, is qu;te similar, as can be seen from their idiograms (Text-Figs. 2 and 4). In both the species, no SAT-chromosomes could be observed. Costus speciosus shows 2n- 36 chromosomes (Text-Fig. 5). One of the chromosomes exhibits a trabant. All the three species of Zingiber examined, namely, Z. officinale, Z. zerumbet and Z. cassumunar, have the same chromosome number 2n = 22. The somatic metaphase plates of these are illustrated in Text- Figs. 6, 7 and 8. Text-Fis. 9, 10 and 11 represent their respective 9 :~'; ~ ~L ... ,. " )2-. .- " ~, ~,16' ~,'~ , 15 4 '~ ~V V~ II r ]) II r r Ir ~,,~. , wv~.. .. z'v .,.11 ,,,. ,t:1 idiograms. Though the chromosome number happens to be the same in all the three species, there are differences in their morphology. The chromo- somes of Z. officinale are somewhat thin and slender, compared to those of the other two species. The chromosomes can be classified into long, medium and short on the basis of their lengths, although the difference between the long and the medium is not very striking. Classified on this Cytological Studies in the Family ZinEiberaceoe 121 basis, the chrosmosomes can be grouped into 5 long, 4 medium and 2 short pairs. From the point of view of shape, there are 6 pairs of 'rods' (of these 2 pairs belong to the long chromosomes and the rest to the medmm), 3 pairsfG'G', H'H' and IT (Text-Fig. 9), taking the configuration of the letter V (these belong to the category of long chromosomes) and 2 pairs of ' crescents '. The 2 pairs of ' crescents ' are the shortest of the lot, as can be seen in Text-Fig. 9. All the chromosomes exhibit either sub-median or median constriction. In Z. cassumunar (Text-Figs. 8 and 11), there are 11 pairs of somatic chromosomes. The chromosomes are fairly stout and comparable in diameter to those of the species of Costus examined. In almost all these, median or submedian constrictions are exhibited, except the pairs A'A' and IT (Text-Fig. 11). These two pairs have a subterminal kinetochore. Of the 11 pairs of chromosomes, 7 are of the rod-type. Of the remaining 4 pairs, G'G' and H'H' (Text-Fig. 11), take the configuration of the letter V, while the rest of the pairs are short chromosomes of the crescent-type with median constriction. The pair H'H' (Text-Fig. 11) represents the longest chromosomes in the complement. Of the 3 pairs of short chromosomes, only the pair IT (Text-Fig. 11) exhibits subterminal constriction, the rest showing a median constriction. No trabants could be observed though several plates were examined. Zingiber zerurnbet.--The somatic number in this species is 22 (Text- Fig. 7). There is a striking similarity in chromosome morphology to that of Z. cassumunar. This can be seen by comparing their respective idio- grams in Text-Figs. 10 and 11. There is one pair E'E' (Text-Fig. 10) in which one chromosome shows the presence of a satellite at its proximal end. The satellite in its homologue, could not, however, be observed. A comparison of the idiograms of the 3 species of Zingiber studied (Text-Figs. 9, 10 and 11), would show that the chromosomes of Z. officinale are different from the rest, not only in respect of their slender nature, but in their morphology also. In Zingiber offcinale, there are 3 long pairs of V-shaped chromosomes, while in Z. zerurnbet and Z. cassumunar, there are only 2 such pairs of chromosomes. In Z. officinale, there are only 2 pairs of short chromosomes (both the pair showing median constriction) while in Z. zerumbet and Z. cassumunar, there are 3 pairs of short chromosomes (2 pairs of crescents with median constriction and a pair of rod exhibiting sub-terminal constriction). On the other hand, as has been pointed out previously, the chromosome morphology of Z. zerumbet and Z. cassumunar are almost identical as can be seen in Text-Figs. 10 and 1I. 122 T.S. Raghavan and K. R. Venkatasubban Three species of Curcuma have been included in the present study. Of these, Curcuma aromatica and Curcurna amada (Text-Figs. 12 and 13), each shows 2n = 42 chromosomes. Curcuma longa (Text-Fig. 14), on the other hand, exhibits 2n = 62 chromosomes. More than a dozen good plates were examined for confirmation of counts. Sugiura (1936) has, however, given 2n = 64 as the number for the same species. The chromosomes of all the three species of Curcuma are very small, compared to those of the Zingiber species examined. These are rod-shaped with sub-median or sub-terminal centromeres. All the three species resemble one another in the general appearance of their chromosomes. Four species of Kcempferia were studied, namely, K. Gibsoni (2n -- 24, Text-Fig.