Chromosome Numbers in the Coryphoideae1

Transcription

1 Chromosome Numbers in the Coryphoideae1 Robert W. Read Received January 10, 1965 The Fairchild Tropical Garden, Coral Gables, Florida 33156, U. S. A. The Coryphoideae comprise some 34 genera of induplicate palmate and c ostapalmatel eaved palms distributed in nearly all tropical and subtropical regi ons of the world. Of these about 20 genera are represented as mature specimens in cultivation at th e Fairchild T ropical Garden, the Coconut Grove Palmetum (the former Montgomery Estate) a nd the United States Department of Agriculture Plant Introduction Station all near Miami, Florida, U.S.A. The remaining 14 genera are either represented as juvenile plants at the Fai rchild Tropical Garden, (i.e. Brahea, Chelyocarpus, Colpothrinax, Hemithrinax, Johannesteijsman nia, Pholidocarpus, Schippia, and Tessmaniodoxa) or not in cultivation in the United States at all, (Chuniophoenix, Liberbaileya, Haitiella, Maxburretia, Pritchardiopsis, and Wissmannia). Because the identification of some palm species in cultivation has been in confusion, many species already studied by early workers are doubtfully identified. Therefore an attempt has been made to restudy chromosome numbers of species in all genera, wherever available, in order to verify previous findings and to prevent the possibility of using counts from misidentified taxa. Voucher specimens representing all material used for the chro mosome counts reported by the present author are deposited at both the Liberty Hyde Bailey Hortorium, Cornell University and at the Fairchild Tropical Garden. Materials and methods All materials used by the present author for pollen-tube mitotic studies came from the gardens listed earlier. Pieces of inflorescences having flowers at anthesis or buds about to open, are brought into an air-conditioned laboratory and allowed to remain several hours or overnight in order to dry somewhat before pollen is collected or sown. Most of the anthers which open during this time should be relatively free from fungal contamination and will have pollen ready for culture. Pollen is sown on a nutrient medium (100 ppm H3BO3 in water; 0.02% colchicine in distilled water; 5-12% lactose and 5% gelatin) for the study of pollen-tube mitosis. After the medium is heated slightly it is applied to cover glasses by means of a small cotton swab. The pollen is dusted lightly over the surface of the dry medium and the cover glass is then overturned onto a Van Tieghem cell which is lined with moist absorbent paper. The Van Tieghem cells are maintained in an incubation chamber 26 Ž for about 8 hours, or until examination of sample slides indicates that mitosis is taking place. The cover glasses are then processed by placing a drop of acetocarmine on the preparation, a clean slide is lowered over the cover glass until it adheres. Slides are made permanent by means of a vapor-transfer technique described elsewhere (Read 1964). Chromosome numbers The following list (Table 1) brings together the chromosome numbers 1 From work related to a project supported by National Science Foundation Grant No. G and extension No. G. B

2 386 R. W. Read Cytologia 30 Table 1. Chromosome numbers in the Coryphoideae * Indicates counts made by the author and reported here for the first time. Numbers in parenthesis refer to voucher specimens. (to be contiuned)

3 1965 Chromosome Numbers in the Coryphoideae 387 (contiuned) (to be continued)

4 388 R. W. Read Cytologia 30 (contiuned) Fig. 1. Camera-lucida drawings of palm chromosomes, enlarged approximately 1,945 times. a, Chamaerops humilis. b, Cryoso phila aculeata. c, Zombia antillarum. d, Washingtonia filifera. e, Livistona chinensis. f, Serenoa repens. g, Copernica yarey var. yarey h, Nannorrhops ritchiana. i, Sabal palmetto. j, Pritchardia thurstonii. for the subfamily published to date with the addition of more recent work by the author (Figs. 1-3). The nomenclature has been brought up to date except where it is impos sible to determine which species was actually used by former workers. Where the botani cal name used by the original worker differs from that which is presently accepted or is in doubt it is en closed within brackets -[ ]-. It is significant that with the exception of a single genus, Licuala, (reported to have both n=8 and n=14 as haploid numbers), all species repre sented in the

5 1965 Chromosome Numbers in the Coryphoideae 389 present study of the subfamily Coryphoideae have a haploid number of n=18. This number occurs again in Borassus of the Borassoideae, another group of induplicate costapalmate-leaved palms. The same number also occurs throughout the induplicate, pinnate-leaved genus Phoenix which has often been closely associated with coryphoid genera; and again in the anomalous arecoid genus Roystonea, which has reduplicate pinnate leaves. the The size of chromosomes varies considerably within a single genus and even to some extent in a single species or preparation, often depending on the pretreatments amount of squash ing and pressure applied glasses. to the cover However, or there is such a significant differ ence in the size of chromosomes tween certain be groups within the subfamily that it is thought to be worthy of note. Coryphoid genera with a great amount specialization modification inflorescence of floral and of the gen erally have the largest chromo Fig. 2. Photomicrographs of palm chromosomes, corresponding to the camera-ludica drawings in Fig. 1, except j. somes. Chamaerops humilis, Rhapidophyllum hystrix, Trachycarpus fortunei and Rhapis hunzilis, all dioecious or polygamodioecious, have chrom osomes measuring 1.8 to 3ƒÊ in length at pollen-tube mitosis when colchi cine is used. Trithrinax brasiliensis and Cryosophila sp. (aculeata?) are not dioecious but have very condensed and large-bracted inflorescences and Cryosophila species have flowers which are specialized to the degree that

6 390 R. W. Read Cytologia 30 apparently the pistils are not receptive until after the pollen has been shed. Both taxa have large chromosomes measuring 1-2 p. Thrinax, Coccothrinax and Zcnibia have bisexual flowers and are morphologically closely allied, with greatly reduced perianth parts and form a third group, with medium sized chromosomes. And Sabal, Livistona, Corypha, Nannorrhops, Pritchardia, Washingtonia, Acoelorrhaphe, Erythea, Copernicia and Serenoa, with the least modified inflorescences, all have very small chromosomes ,u long with very few up to 2 p in length. Fig. 3. Photomicrograph and camera-lucida drawing of the chromosomes of Coccothrinax argentata, the Florida silver-palm. 2,700 ~. This photomicrograph was made with the aid of a Reichert Phase-contrast microscope, recently acquired for cytological work. Literature Bosh, Erich Blutenmorphologische and zytologische Untersuchen an Palmen. Ber. Schweiz. Bot. Ges. 57: Bowden, W. M A list of chromosome numbers in higher plants. Amer. Jour. Bot. 32: 193. Darlington, C. D. and Janaki-Ammal, E. K Chromosome Atlas of Cultivated Plants. Allen and Unwin, Ltd., London. Eichorn, Andre Etude caryologique des Palmiers. I. Revue Cytol. et Biol. Vegetales 14: Nouvelle contribution a l'etude caryologique des Palmiers. Revue Cytol. et Biol. Vegetales 18: Olah, Leslie V The cytology of Corypha umbraculifera L. Part I. Ann. Bogor 1: Cytology of Corypha elata Roxburgh: The behavior of the nucleus during meiotic prophase. Bull. Torrey Club 89: Read, Robert W Palm Chromosomes, Principes 7: cited

7 1965 Chromosome Numbers in the Coryphoideae Palm chromosome studies facilitated by pollen culture on a colchicine-lactose medium. Stain Tech. 39: Sato, D Karyotype alteration and phylogeny VI. Karyotype analysis in Palmae. Cytologia 14: Sharma, A. K. and Sarkar, S. K Cytology of different species of palms and its bearing on the solution of the problems of phylogeny and speciation. Genetica 28: Sinoto, Y Chromosome studies in dioecious plants with special reference to the allosomes. Cytologia 1: Venkatasubban, K. E Cytological studies in Palmae, Part I. Chromosome numbers in a few species of Palms of British India and Ceylon. Proc. Indian Acad. Sci. 22: