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306 Cytologia 21

Cytological Studies in l-lelobiae, I. Chromosome idiograms and a list of chromosome numbers in seven families1

Ititaro Harada Biological Institute, Faculty of Science, Nagoya University, Nagoya

Received Decemnber 27, 1955

Introduction

As a part of the cooperative work on the karyotypic investigations of monocotyledonous , directed by Dr. Y. Sinoto, the writer has been studying the Helobiae since 1940. The writer will report the cytologi cal evidences, principally the karyotypic analyses in seven families of Helobiae. The Order Helobiae, otherwise called Helobiales, Fluviales or Najadales, is a unique group in Angiosperms, growing in aquatic habitat. Further, from several points of view, Helobiae is regarded as a systematically or phylogenetically important group. It is said that Helobiae is an ecological group involving those plants growing in fresh water or marsh and in sea or brackish water. "Sea grasses ", the submarine phanerogamous plants, are found solely in Helobiae. Growing surroundings of each are as follows2:

1. Potamogetonaceae emerg. flow. and some with (Althenia) brackish water, submerged fl oat. leav. (Cynzodocea) sea water, submarine 4. Scheuchzeriaceae (Diplanthera) sea wat., submar. (Lilaea) marsh Phyllospadix sea wat., submar. (Maundia) marsh (Posidonia) sea wat., submar. Scheuclazeria marsh Potarnogeton fresh or brackish wat., sub (Tetroncimn) marsh merged, with floating and Trigloehin freshwater marsh or seaboard emerging . marsh Ruppia brackish or sea wat., submerg. 5. or submar. Alisma Zannichellia brack. or fr. wat., submerg. (Burnatia) 2. Najadaceae Caldesia fr. wat., submerg. (Damasonium) 3. Aponogetonaceae Echinodorus Aponogetonn fr. wat., submerg., with (Elisma) fr. wat., submerg.,

1 The principal part of the work was carried out from 1940 to 1950 at The Cytogenetical Laboratory, presided over by Dr. Yosito Sinoto, of Botanical Institute, Faculty of Science, University of Tokyo. 2 Classification of the genera is after Engler's sytem (Engler, A. and Diels, L. 1936. Syllabus der Pflanzenfamilien , llte Aufl.), Chromosome numbers of those in parenthesis have not as yet been studied. 1956 Cytological Studies in Helobiae, 1. 307

Limnophyton with float. leva. and leav. and emerg, flow. (Lophotocarpus) emerg. flow.; marsh Limnocharis marsh (Ranalisma) Tenagocharis marsh (Rautanenia) 7. fr. wat., submerg. () (Boottia) fr. wat., submerg., with emerg. 6. Butomaceae flow. Butomus marsh Elrodea fr. wat., submerg., with float. Hydrocleis fr. wat., submerg. with float. flow.

Figs. 1-35. Potamogetonaceae. ca. •~2200. 1-2, Phyllospadix (RT): 1 a, P. iwatensis

(•Š). 1 b, P. iwatensis (_??_). 2 a, P. japonica (•Š). 2 b, P. japonica (_??_). 3-22, Potamo

geton (RT): 3, P. alpinus. 4, P. anguillanzcs. 5, P. apertus. 6, P. biwaensis. 7, P. crispus. 8, P. cristatus. 9, P. dentatzas. 10, P. distinctus. 11 a and b, P. Fauriei.

12, P. Fryeri. 13, P. gramineas. 14, P. lcanzogawaensis. 15, P. Maackianus. 16, P,

malaianus. 17, P. malainoides. 18 a, b, c and d, P. mnonoginus. 19, P. natans. 20, P.

nipponicus, 21, P, numasalcianas. 22, P. oxyphyllus. 308 I. Harada Cytologia 21

() sea wat., submar. emers., flow. sea wat., submar.H fr. wat., submerg., with emerg, ydrilla fr. wat., submerg. fl ow. fr. wat., submerg., with fr. wat., submerg., with emerg. float. leav. and emerg. flow. fl ow. () fr. wat., submerg., with () sea wat., submar. emerg. flow. Trianea fr. wat., submerg. () fr. wat., submerg., with fr. wat., submerg.

Figs. 23-35. 23-28, Potamogeton (RT): 23 a and b, P. panormitanus. 24, P. pectinatus. 25, P. perfoliatus. 26, P. praelongus. 27, P. pusillus. 28, P. Vaseyi. 29, Ruppia maritima. ca. x2200 . a (RT), b (PMC-I). 30, Zannichellia palustris. ca. x2200. a (RT), b (PMC-I). 31-35, Zostera. ca. x2200. 31, Z. asiatica (RT). 32, Z. caespitosa: a (RT), b (PG-I). 33, Z. caulescens: a (RT), b (PG-I). 34, Z. marina: a (RT), b (PMC I), c (PG-I). 35, Z. nana (RT). 1956 Cytological Studies in Helobiae, 1. 309

It is one of the writer's aims to reveal some relationship between these ecolo gical surroundings and the cytological evidences. So far, however, the writer has detected nothing tangible about it, especially about a plausible relationship between the aquatic habitat and the karyotypic characteristics. But some of the submerged limnetic species and, as far as studied, all species of submarine sea grasses exhibit respectively the characteristic form and the polli

Figs. 36-44. Najas. ca. •~1700. 36, N. ancistrocarpa (RT). 37, N. foveolata (RT).

38, N. gracillima (RT). 39, N. graminea (RT). 40, N. major: a and b (•Š, RT), c and

d (_??_, RT), e (PMC-I), f and g (PG-I). 41, N. minor (RT). 310 I. Harada Cytologia 21 nation pattern, revealing an elaborate adaptation to the aquatic surroundings. For long it has been said by several botanists that Helobiae was a group having the phylogenetically most primitive type in and could be regarded as a stock in the phylogenetical development of Monocotyledons. Moreover, many botanists have assumed that HeIohiae was standing in a joint

Figs. 42-47. 42, N. oguraensis (RT). 43, N. tenuicaulis (RT): a (•Š), b (_??_). 44, N. sp.

45, Aponogeton distachyus, ca. •~2200. a (RT), b (PMC-I), c (PG-I). 46 and 47, Scheu chzeriaceae. ca. •~2200. 46, Scheaehzeria palustris (RT). 47, Triglochin maritimum:

a and b (RT), c (PMC-I). ing point between Dicotyledons and Monocotyledons; especially a phylogenetical relationship between Ranales and Helobiae has been often discussed. The first cytological work on this problem was published by Liehr (1916). With the same idea, principally from the karyotypic standpoint , the present writer studied the chromosome number of some water plants in Ranales and of 1956 CytologicalStudies in Helobiae, I. 311

other dicotyledonous water plants (Harada 1952). Further, for a contribution to the cyto-phylogenetical relationship of Helobiae, the writer studied the chromosome number of Pandanales (Harada 1949 a), which is systematically arranged in closer rank to Helobiae in Engler's system and is also regarded as one of the more primitive groups in Monocotyledons. Considerations concern

Figs. 48-53. Alismataceae. ca.•~1700. Figs. 48 and 49. Alisina: 48, A. eanatieutatum, a (RT), b (PMC-I). 49, A. orientale, a (RT), b (FMC-I). 50, Caldesia renaformis, a (RT), b (PMC-I). 51-62, Sagittaria: 51, S. ayinashi, a (RT), b (PMC-1). 52, S. falcata (RT). 53, S. montezidensis, a (RT), b (PMC-I).

ing the cyto-phylogenetical relationships above mentioned will be reported in

detail in later papers of the series "Cytological Studies in Helobiae" by the

writer. 312 I. Harada Cytologia 21

In the present paper are given the idiogramatical figures of chromosomes of 22 genera of 7 families and a list of chromosome numbers of 27 genera including the results obtained by several authors. Although some of the figures in the text and of the numbers of chromosomes in the list were already reported by the writer, they are again included in the present paper, since

Figs. 54-60. Aliomataceae. 54, S. natans, a (RT), b (PMC-I), c (PG-I). 55, S. platy phylla (RT). 56, S. pyymaea, a (RT), b (PMC-I), c (PG-I). 57, S. subulata, a (RT), b (PMC-I), c (PG-I). 58, S. trifolia (RT). 59, S. trifolia form. longiloba (RT). 60, S. trifolia form. plena (RT). most of them were published in preliminary brief notes in Japanese with or without figures, or printed as given in lectures before meetings of the Socie 1956 Cytological Studies in Helobiae, I. 313 ties. In later papers of this series the writer will report fully karyotypic an alyses of each group, i.e. of genera or of families, the microsporogenesis and the pollination of some species, and other cytological evidences in a number of species.

Figs. 61-65. 61, S. trifolia form. ,jzitensis, a (RT), b (PMC-I), c (PG-I). 62, S. trifolia

var. sinensis form. eoerulea, a (RT), b (PMC-I). 63-65, Butomaceae. ca. •~1700. 63,

Butomus umbellatus (RT). 64, Hpdrocleis nym,phoides, a (RT), b (PMC-I). 65, Limno charis (lava, a (RT), b (PMC-I).

Acknowledgment

It is a pleasure to record here a debt of gratitude to Dr. Yosito Sinoto for his general guidance and his ceaseless encouragement given the writer to 314 I. Harada Cytologia 21

carry out this work, especially for his plotting the object of research, the karyo typic analysis of Helobiae. Further, the writer wishes to express his hearty thanks to Dr. Shigeru Miki1 who permitted the use at will of the several water plants cultivated by him for the writer's cytological materials, and who always rendered to the writer adequate aid in collecting the plants in several localities and identifying the names of species collected. The writer is in

Figs. 66-78. Hydrocharitaceae . ca. •~2200. 66-68, Blyxa (RT): 66, B. ceratosperma.

67, B. Japonica. 68, B . sp. 69 and 70, : 69, E. canadensis, a (•Š, RT), b (_??_, RT), c (PMC-I). 70, E. densa, a (_??_, RT) , b (PMC-I). 71, Halophila ovata, a (•Š, RT), b (_??_, RT), c (PMC-I), d (PG-I).

1 Dr. S, Miki was until 1948 associated with The Botanical Institute, Faculty of Science, Kyoto University, and is now with The Institute of Polytechnics, Osaka City Unversity. 1956 Cytological Studies in H elobiae, I. 315

Figs. 72-78 . 72, zerticillata (RT). 73, Hydrochariss asiatica, a (RT), b (PMC I). 74, , a (RT), b (PMC-diakinesis). 75-78, Vallisneria (RT): 75, V, asiatica, a (•Š) , b (_??_), c (unknown as to the sexuality). 76, V. asiatica var. biwaensis. 77, V. denseserrulata, a (•Š), b (_??_). 78 a and b, V. sp. 316 1. Harada Cytologia 21

debted as well to various members of Dr. Y. Sinoto's Laboratory in University

of Tokyo, especially to Dr. Tadamasa Miduno, Dr. Dyuhei Sato and Dr.

Nobunori Tanaka for their advices.

Materials and methods

The majority of plants of Helobiae is wild aquatic weeds; the writer was

successful in collecting almost all of the Japanese species thanks to the direc

tion by Dr. S. Miki. Some of them collected were transported in pot or basin

in the Laboratory field and were used for cytological studies. In the Botanical

Garden of Kyoto University many species of water plants were collected and

cultivated by Dr. S. Miki, some of which as follows were used for study by

the writer: Pota7nogeton, Zannichellia, Najas, Sagittaria, Butornus and

Elodea. Aponogeton, Hydrocleis, Limnocharis and three species of Sagit

taria (S. montevidensis, S. natans and S. subulata), all ornamental plants,

were obtained in florists or in botanical gardens. and its

varieties or forma cultivated as the esculent plants were got from farmers.

Root tips were fixed with either Navashin's solution or Bonn-modification of

Flemming's solution and sections made by the usual paraffin method were stained

with gentian violet after Newton's method or with Heidenhain's iron-haematoxy

lin; staining with fuchsine after Feulgen's method was employed in cases where

tips had different cytoplasmic inclusions. Pollen mother cells and young

pollen grains were smeared and stained with acetic carmine for observation of reduced chromosome set; otherwise, buds were fixed with Carnoy's

fluid, or with Bouin's or Navashin's solutions and then preserved in 75%

alcohol; on occasion, of the preserved buds the anther sacs were taken

out and smeared in acetic carmine , or following the course of the ordinary paraffin method the sections of these buds were stained with either gentian violet or baematoxylin.

The figures were drawn with Abbe's drawing apparatus. Magnification of figures represented in the text is for the most part ca. •~2200 , except for Najas, Alismataceae and Butomaceae where it is ca. •~1700, as shown in the explanation of figures respectively. The abbreviations used in the explana tion of figures are as follows: RT=root tip, PMC-I=the first meiotic me taphase of pollen mother cells, and PG-I=metaphase of the first mitosis of pollen grains.

Results

Chromosome numbers, viz. somatic numbers 2n in root tips and reduced numbers as n in microsporogenesis or microgametogenesis, are given in the list, including the results obtained by the previous authors. Details of the

Dr. Y. Sinoto has presided over The Cytogenetical Laboratory, Botanical Institute,

Faculty of Science , University of Tokyo, until his retirement in 1953. 1956 CytologicalStudies in Helobiae, I. 317 results obtained by the writer will be reported in later papers, but a few brief remarks will be given here. 1) The karyotypes of each group (families, genera, subgenera, etc.) or of each species of Helobiae represent various types; the writer has no success to find out any common and unique characteristics as to the karyotype throughout Helobiae. Any karyotypic properties related to the aquatic habitat are not detectable. 2) Among every seven families there are some which exhibit common karyo typic characteristics while there are others which involve species or groups having various karyotypes. The former is as follows: Najadaceae, Scheu chzeriaceae, Alismataceae and Butomaceae. The latter is as follows: Potamo getonaceae and Hydrocharitaceae. In this respect there is nothing to be said concerning the family Aponogetonaceae, because its cytological studies are scanty.

3) Potamogetonaceae

a) The genus Phyllospadix, a sea grass unique to the northern coast, has an interesting chromosome complement, possessing the "multiple sex

chromosomes" (•Š: 2n=20=10 autosomes+10Xs, _??_: 2n=16=10 autosomes

+5Xs+Y; Harada 1944 and Harada unpubl.) . The male plants are also found which represent 2n=17=16+Y, and 2n=18=17+Y (Harada 1949 b).

Further, a monoecious clone, having both female and male flowers in one and the same inflorescence, is found and its karyotype is of the female type,

i.e. 2n=20 (Harada unpubl.). These evidences may contribute to the solving of the problem of sexuality and sex chromosome. Chromosome Y represents itself as a distinct heteropycnotic body in the interphasic or metabolic nucleus.

Such a heteropycnosis is found first in Phanerogams.

b) Species of Potanzogeton may be arranged into two polyploid series consisting of basic numbers b=13 and 14.

c) Ruppia maritima of Japan is a high polyploid type in comparison with foreign ones. Its karyotype is a so-called Yucca-Agave type.

d) As to the genus Zannichellia there is nothing to be mentioned in detail karyotypically.

e) All species of the genus Zostera, a cosmoplitan sea grass, have 2n =12 as far as studied by the writer and others; the genus may be considered as one of the so-called homopolid types.

4) Najadaceae (possessing only one genus Najas)

a) In the subgenus Caulinia, a monoecious group, almost all the species represent a polyploidy with wide ranges among inter and intra-species. The subgenus, therefore, may be named as a group of so-called "oscillating chromosome numbers" and regarded as standing in an unstable step of evolu tion (Harada 1943a and Chase 1947)

b) Najas major belonging to the subgenus Eunajas, a dioecious group, has been long studied by several investigators. However, no polyploidy has 318 1. Harada Cytologia21 been found as yet. About the occurrence of sex chromosome some arguments were presented. In 1943a the writer also reported that male plants have a sex chromosome Y; but by a closer investigation it was revealed that it was an oversight and the concerned chromosome (Y) was merely an extra chro mosome which could have no relation to the expression of sexuality (Harada 1954). Nuclear plates with various chromosome numbers (n=5, 6, 7 and 8) were often observed in the mitosis of pollen grains (Harada 1943 b) and not infrequently were also observed different abnormalities in the anaphase of the second meiotic division of pollen mother cells, in the pollen tetrads and in the pollen grains in early stage. 5) Aponogetonaceae (possessing only one genus Aponogeton) Intra-specific polyploidy may be recognised in A. distachyus. 6) Scheuchzeriaceae a) In Triglochin there exist inter and intra-specific polyploidy; speci mens collected in Okayama Pref. (Western Japan) have 2n=48, while those in Tiba Pref. (Eastern Japan) and in Hokkaido (Northern Japan) have 2n= 120 respectively. b) About the genus Scheuchzeria there is nothing to be mentioned in detail karyotypically. 7) Alismataceae All genera, as far as studied, exhibit throughout a characteristic karyo type having larger chromosomes; it is desirable to research another genera not yet studied karyotypically. a) The species of Alisma have so different chromosome numbers, reveal ing inter and intra-specific polyploid or heteroploidy, that it is difficult to decide any basic number by means of simple comparison of karyotypes. b) Also in Echinodorus ranunculoides different numbers of chromosome are remarked as in the species of Alisma. c) In the genus Sagittaria, on the contrary, all species studied have one and the same karyotype; in respect to the chromosome number the genus would be called as a typical homoploid one (2n=22). d) The karyotype of Caldesia is strictly the same as Sagittaria. e) Concerning the karyotyps of Limnophyton there is nothing to be mentioned in detail. 8) Butomaceae a) Karyotypes in this family resemble those in Najadaceae and Hydro charitaceae. The genus Butomus is regarded as a karyo-phylogenetically in teresting one, having a karyotype of the so-called Yucca-Agave type. How ever, that may be, the karyotyps of Ruppia (Potamogetonaceae) is a more typical Yucca-Agave type (see 3)c). Also systematically the family Butoma ceae is regarded as an important group. Butoinus umbellatus exhibits an occurrence of intra-specific polyploidy. b) As to another genera of the family, e. g. Hydrocleis, Limnocharis 1956 Cytological Studies in Helobiae, I. 319

and Tenagocharis, there is nothing to be mentioned in detail concerning the karyotypical evidences. 9) Hydrocharitaceae a) In the genus Blyxa an occurrence of inter-specific polyploid is remarked. b) As to the genera Hydrocharis and Ottelia some evidences will be referred to later papers. Hydrocharitaceae involves genera some of which possessing dioecious plants: c) Sex chromosomes in the genus Elodea are famous for being the first in the history of discovery. In two species of Elodea the writer has not so far succeeded in identifing the sex chromosomes, X and Y; chromosomes of Elodea are considerably small; the writer will study more closely the nature of sex chromosomes of Elodea in abundant materials. d) In the genus Hydrilla a relationship of sexuality and karyotype was suggested by Sinoto (1928 and 1929); in this respect the writer's data will be reported in detail in later papers. e) The genus Halophila, a sea grass in temperate and tropical zones, is dioecious; but the karyotypes of female and of male are one and the same. f) In the genus Vallisneria there was some dispute on the occurrence of sex chromosomes. Every species studied by the writer has an identical karyotype in the female and the male. Several karyotypical aberrations, mainly dimensional, are observed among inter and intra-species.

Table 1. List of chromosome numbers of 7 families in Helobiae (), computed number as n. (()), computed number as 2n. *, after Tischler 1950. **, after Love and Love 1948. ***, after Love and Love 1944. ****, after Darlington and Janaki Ammal 1945. ***, after Blackburn 1929.

1 See the text p . 317.

Cytologia 21, 1956 22 320 I. Harada Cytologia 21 1956 Cytological Studies in Helobiae , I. 321 qqq I. Harada Cytologia 21

1 See the text p . 318. 1956 Cytological Studies in Helobiae, 1. 323 324 I. Harada Cytologia 21 1956 Cytological Studies in Helobiae, 1. 325

1, 2, 3 Unknown as to the sexuality in the material plants used, 326 I. Harada Cytologia 21

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Cytologia vol. 21, no. 3 (pp. 223-328) Issued October 30, 1956 Ausgegeben am 30, Oktober 1956 Paru le 30 octobr. 1956