CARYOLOGIA
Vol. 52, n. 1-2: 59-64,1999
Karyomorphology of eight taxa of Hymenocallis
from South India
G. JEE and B. VIJAYAVALLI1 *
Tropical Botanic Garden and Research Institute, Pacha, Palode, Thiruvananthapuram - 695 562, India. 1
Department of Botany, University of Kerala, Kariavattom, Thiruvananthapuram - 695 581, India.
Abstract — Karyotypes of eight taxa of Hymenocallis Salisb. viz., H. harrisiana Herb
(2n=74), H. littoralis Salisb. (2n=46), H. speciosa Salisb. (2n=54), H. rotata Salisb. (2n=46), H.
occidentalis Kunth. (2n=46), H. daphe Herb. (2n=42, 44 and 46) were studied. It is suggested
that polyploidy and aneuploidy have contributed significantly in the evolution of
chromosomes in the genus and n=23 is the secondarily derived basic number for the genus.
Key words: aneuploidy, chromosome evolution, Hymenocallis, karyomorphology, polyploidy.
INTRODUCTION
Hymenocallis Salisb., an entirely American
genus of the family Amaryllidaceae with about
100 species distributed along the warmer parts
of North, South and Lateral America as well as
West Indies (FLORY 1976). The different species
of the genus Hymenocallis studied so far
evince 46 and from 60 to 100 as their somatic
chromosome constitution (JANAKI AMMAL 1945).
The karyomorphological details of several
species have been worked out by many authors
(NAWANKITI 1985; FLORY 1975, 1976; MEHRA and
SACHDEVA 1976; SHARMA and BAL 1956; SATO 1947).
However, karyomorphological data of tropical
South Indian species is very much lacking.
Moreover inspite of the apparent general
similarity among the different species of
Hymenocallis, they envisage karyomorphological
diversity in finer details. Results of the
karyotype of these species are reported here.
MATERIALS AND METHODS
Plant specimens were collected from different localities of Tropical South Indian states of Kerala and
Tamil Nadu. Chromosome numbers were determined
from root tip cells. Root tips were allowed a
* Corrisponding author: fax +91-471-433977.
pre-fixation treatment in 0.002 M aqueous solution
of 8-hydroxy-quinoline for 3 h at 4°C. The chromosomes were stained in 2% acetocarmine. Photomicrographs were taken from temporary preparations.
Karyomorphological analysis was made following
STEBBINS (1958) and LEV AN et al. (1964).
RESULTS
The karyotype details of the eight taxa presently studied are given in Table 1 and idiograms
in Figs. 8-15. H. harrisiana showed 2n—74 chromosomes, H. littoralis 2n=46, H. speciosa
272=54, H. rotata 2n=46, H. occidentalis 2n=46
chromosomes, while three accessions of H. daphe
carried 2n=42, 44 and 46 chromosomes each
(Figs. 1-7). In H. littoralis chromosome 2 and 7
exhibited size heteromorphism between its
members of homologue, chromosome 21 was
heteromorphic with only one of the pair having
a satellite in H. speciosa and in H. occidentalis
chromosome 3 showed size heteromorphism.
DISCUSSION
Of the 8 taxa currently studied 4 belonged
to the karyotype category 2B, 3 to 3B while 1
was of 2C type. Karyomorphological data suggested no evidence of gross structural alterations of chromosomes both within and between
different species. Although H. speciosa fell into
60
the category 2C, their chromosome size showed
remarkable resemblance with their counterparts,
but for the satellite on one of the homologous
members of chromosome 21. It has also been
observed that some of the chromosome of the
basic types were duplicated 2 , 3 or 4 times in
almost all taxa studied. Inspite of the general
agreement in chromosome numbers, gross total
amount of chromatin matter among different
species of Hymenocallis, on many occasions the
observations on structural details of the karyotype were not in perfect harmony with each
other, thus rendering the possibility of evolving a
basic karyotype for the different taxa as a whole
futile. The presence of 2n=46 has been reported
in H. littoralis by many authors (SATO 1938; SNOAD
1963; RAIN A and KHOSHOO 1971) including the
present study. However their observations on
structural details of karyotype were often far from
congruity. RAINA and KHOSHOO (1971) and SNOAD
(1963) envisaged the association of 8 metacentric,
35 submetacentric and 3 subtelocentric
chromosomes which is contrary to present as
well as earlier studies. The currently studied H.
littoralis reveals 25 m-, 19 sm- and 2 st type of
chromosomes, thus the absence of telocentric
chromosomes finds parallel with the report of
SHARMA and BAL (1956) in classifying H. littoralis
to be an "atelocentric"
JEE and VIJAYAVALLI
species of the genus Hymenocallis. The present
observation of 10 telocentrics in H. daphe with
2n=46 is contrary to the contention of FLORY
and SCHMIDHAUSER (1959) that teleocentrics are
not found in plants accounting for 2n-46 or 69 or
40. FLORY (1976) has cited instances of
centromeric misdivision in 2n=46 species resulting in taxa with chromosome numbers in
which metacentric chromosome got replaced by
telocentrics.
Another feature observed was that the ACL
(average chromosome length) of different taxa
presently studied showed a proportionate increase or decrease with respective increase or
decrease in chromosome numbers ie., ACL reduced with increase in chromosome number and
vice versa. The data reveal that the genus
exhibits chromosome numerical dynamism at
both intra-and inter-specific levels, the like of
which is not prevalent in any other genera of the
family. The genus exhibits an array of chromosome numbers which are based on n=23 which is
ostensibly too high and therefore should be a
secondarily derive one. SATO (1938) and SNOAD
(1955) regarded n=23 as the basic number of the
genus since a majority of the species possessed
2n=46. SHARMA and BAL (1956) considered both 22
and 23 as possible base numbers because of the
presence of 2n=44 and 2n=46.
KARYOMORPHOLOGY OF HYMENOCALLIS
Figs. 1-7. — Somatic chromosomes oiHymenocallis. 1. H. harrisiana, 2n=74. 2. H. littoralis, 2n=46. 3. H. rotata, 2n=46. 4. H. occidentalis, 2n=46. 5. H. daphe, accession I, 2n=44. 6. H. daphe, accession II, 2n=42. 7. H. speciosa, 2n=54. x900.
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JEE and VIJAYAVALLI
Figs. 8-11. — Idiograms of the haploid complements of Hymenocallis. 8. H. harmiana, 9. H. daphe, accession III. 10. H. littoralis. 11. H.
speciosa.
(1963) believed n=23 to be of dibasic
origin, the two primary basic numbers involved
are x=ll, which is common in the family and
x=12 found in H. quitonensis, while RAINA and
SNOAD
(1971) suggested 3 basic numbers of
x=10, 11 and 12 for the genus. However all of
them agree that this is of secondary origin. Further presence of more than one chromosome
KHOSHOO
KARYOMORPHOLOGY OF HYMENOCALLIS
63
Figs. 12-15. — Idiograms of the haploid complements of Hymenocallis. 12. H. rotata. 13. H. occidentalis. 14. H. daphe, accession II. 15. H.
daphe, accession I.
number in several species has been observed.
The 3 accessions of H. daphe currently studied
revealed the presence of 2=42,44 and 46 chromosomes as their somatic complement. The ex-
istence of variation go on to prove the extent of
role played by polyploidy and aneuploidy in the
evolution of chromosome in this genus. STEBBINS (1971) has held that by far the common
64
JEE and VIJAYAVALLI
variation in chromosome numbers in vascular
plants are doubling and higher multiplication of
entire chromosome sets and that aneuploid
variation from series in which gametic numbers
of related species form consecutive series, or
more rarely they differ each other by 2 or more
chromosome. Further the complex chromosome
situation in Hymenocallis shows that the genus
is in an evolutionarily dynamic state with
significant degrees of cytological euploidy and
aneuploidy as well as chromosome repatterning
prevalent.
REFERENCES
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Chromosome numbers for several species of
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—, 1976. — Distribution, chromosome numbers and types of
various species and taxa of Hymenocallis. Nucleus, 19: 204227.
FLORY W.S. and SCHMIDHAUSER T.P., 1957. — Mitotic chromosome
numbers in Hymenocallis with a consideration of factors
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JANAKI AMMAL E.K., 1945. — In: A. Janaki and C.D. Darlington
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LEV AN A., FREDGA K. and SANDERBERG
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Received 26 April 1999; accepted 30 May 1999.