Cytologia 46: 149-160, 1981

Cytotaxonomy of 11. Chromosome number and karyotype analysis of Thespesia, , , and .

Aparna Dasgupta and R. P. Bhatt1 Departmentof Pharmacy,S. V. Govt. Polytechnic, Bhopal(M. P.), India ReceivedMay 22, 1979

The family Malvaceae comprises 88 genera and 2300 species, distributed in warm temperate and tropical regions of the world (Hutchinson 1967). The mem bers of the family have been studied by a number of taxonomists, but the views expressed by them concerning delimitation of various taxa are different. The cytological work in the family has been attempted by a number of workers. Most of the earlier works were confined to reports of chromosome numbers of various taxa, though the cultivated or ornamental taxa were worked out in detail. There is no consensus in the conclusions drawn regarding the basic number or numbers and the envisaged phylogenetic relationships in these works. In the present work an attempt is made to understand the phylogenetic re lationships of the allied taxa and to evaluate their systematic positions as understood at present. The genus Hibiscus, Thespesia and Abelmoschus selected for the present in vestigation belong to the tribe Hibisceae while Pavonia and Malachra belong to the tribe Ureneae. Detailed analysis of the karyotype of one species of Thespesia i.e. T. populnea has been carried out. Five species of the genus Hibiscus were studied viz H. mutabilis, H. trionum, H. hirtus, H. ovalifolius and H. caesius. In the avail able literature chromosome number is reported for H. ovalifolius, but karyomor phological study has been done for the first time here. A new report of chromo some number is made for H. caesius and its karyomorphology is studied. Two species of Abelmoschus i.e. A. manihot and A. angulosus are taken. The somatic chromosome number and karyotype analysis of A. angulosus has been done for the first time. Two species of Pavonia are studied. It is apparent from the available literature that the species P. zeylanica has remained unexplored cytologically, which has been done in the present study. Detailed karyomorphology has been done for the first time in P. patens. One species of Malchra i.e. M. capitata is included in the present work.

Materials and methods

Source of the material Taxa Source

1 Department of Botany, Faculty of Science, M. S. University, Baroda, India. 150 Aparna Dasgupta and R. P. Bhatt Cytologia 46

Hibiscus mutabilis Linn. Dehra Dun Hibiscus trionum Linn. Kolar Hibiscus hirtus Linn. Baroda Hibiscus ovalifolius (Forsk.) Vahl Harani Hibiscus caesius Garcke Chhotaudepur and Vasad Abelmoschus manihot (Linn.) Medik. Rajpipla (Steud.) Wt. and Arn. Dehra Dun Thespesia populnea (Linn.) Soland. Baroda and Pavagadh Malachra capitata Linn. Khedbrahma and Baroda Pavonia zeylanica Cav. Baroda, Vasad Pavonia patens (Andr.) Chiov. Kutch

The seeds collected from different localities were given separate voucher num bers and voucher specimens were deposited in departmental Herbaria. All collec tions were grown in Botanical Garden, the M. S. University of Baroda, for cytolo gical investigations. Excised root tips were pretreated with saturated solution of para-dichlorobenzene (Meyer 1945) and fixed in acetic-alcohol mixture. Tjio and Levan's (1950) aceto-orcein squash technique was adopted for mitotic preparation.

Drawings were made at table level on a steindroff research microscope using

E. Leitz Wetzler cameralucida apparatus at 30•~120 (apochromat) magnification, chromosomes with satellites and secondary constriction are represented by out lines.

Observations

For better comparison of karyotypes uniform categorization based on size difference and the ratio of short arm/long arm (R1) and long arm/short arm (R2)

(Adhikary 1974) was made. The chromosomes of all the investigated species can be classified into the following types. Type A and B

Long chromosomes (more than 5ƒÊ) with nearly median (nm) and nearly sub median (nsm) centromeres respectively.

Types C, D and E

Medium chromosomes (3ƒÊ to less than 5ƒÊ) with median (M), nearly median

(nm) and nearly sub-median (nsm) centromeres respectively. Types F, G and I

Short chromosomes (1ƒÊ to less than 3ƒÊ) with median (M), nearly median

(nm) and nearly sub-median (nsm) centromeres respectively. Types J, K and L

Very short chromosomes (less than 1ƒÊ) with median (M), nearly median (nm) and nearly submedian (nsm) centromeres respectively.

In the different types of chromosomes values of R1 and R2 are the following: Median (M) =R1 and R2=1.0 Nearly median (nm) =R1=0.99-0.61 and R2=1.01-1.63 Nearly Submedian (nsm)=R1=0.60-0.34 and 0.32-0.23 1981 Cytotaxonomy of Malvaceae II. 151

and

R2=1.64-2.99 and 3.01-4.26

Super script:

S Denotes satellites (SATs)

S•L Denotes Secondary constriction on long arm

(Sec. Cons.)

Table 1. Chromosome numbers in investigated taxa

Tribe: Hibisceae

Genus; Hibiscus Linn.

1. H. mutabilis Linn.

2n=120=F6+G62+Gs4+Gs•L2+I38+Is2+Is4•L+L2

The present report of 2n=120 is not in agreement with the earlier reports Table

1. The karyotype analysis reveals the presence of 3 pairs (F-type) of chromosomes

with median, 34 pairs (G-type) with nearly median and 23 pairs (I and L-types) with

nearly submedian centromeres (Figs. 9 and 6a). Chromosomes are short to very

short sized, ranging in length from 2.55ƒÊ to 0.94ƒÊ with a mean length of 1.51ƒÊ. 152 Aparna Dasgupta and R. P. Bhatt Cytologia 46

Figs. 1-8. Somatic metaphase plates of T. populnea, H. ovalifolius, H. caesius, P. patens, H. trio num, P. zeylanica, M. capitata, and H. hirtus, respectively. 1981 Cytotaxonomy of Malvaceae II 153

Figs. 1a-8a. Idiograms of T. populnea, H. ovalifolius, H. caesius, H. trionum, H. hirtus, H. muta bilis, A. angulosus, and A. manihot, respectively. 154 Aparna Dasgupta and R. P. Bhatt Cytologia 46

In the work of Sharma and Sharma (1962) satellited and secondarily constrict ed chromosomes are represented by 6 and 7 pairs in the complements of 84 and

110 chromosomes respectively. However, 6 pairs of chromosomes with satellites and secondary constrictions are observed in the complement of 120 chromosomes in the taxon analysed at present (Figs. 9 and 6a).

2. H. trionum Linn.

2n=56=D2+G32+Gs4+Gs2•L+I16

Earlier reports of other workers except that of Medvedeva (1936), Nakajima

(1936); Rao (1941) and Kachecheba (1972) i.e. 2n=28 are confirmed in the present study (Table 1). The complement is seen to consist of 20 pairs (D and G-types) with nearly median and 8 pairs (I-type) of chromosomes with nearly sub-median centromeres (Figs. 5 and 4a). Chromosomes are medium to short sized, ranging in length from 3.32ƒÊ to 1.53ƒÊ with a mean length of 2.22ƒÊ.

Figs. 9-11. Somatic metaphase plates of H. mutabilis, A. angulosus and A. manihot respectively.

Rao (1941) reported 3 pairs of chromosomes with satellites (Trabants) in the taxon analysed by him. In the present study, 2 pairs of SAT-chromosomes (G" type) and 1 pair (Gs•L-type) of secondarily constricted chromosomes in the somatic complement are observed (Figs. 5 and 4a).

3. H. hirtus Linn.

2n=64=G36+Gs•L2+I24+Is2

The present report of n=32 and 2n=64 is different from that of Sharma and

Sharma's (1962) report i.e. 2n=70 (Table 1). The somatic complement consists

of 19 pairs (G-type) of chromosomes with nearly median centromeres and 13 pairs

(I-type) with nearly sub-median centromeres (Figs 8 and 5a). Chromosomes are short sized, length ranges from 2.38ƒÊ to 1.02ƒÊ with a mean length of 1.55ƒÊ.

Karyomorphological studies of Sharma and Sharma (1962) reveals the pre

sence of 3 pairs of secondarily constricted and 2 pairs of satellited chromosomes in

the taxon they have analysed. In contrast to this, only 1 pair of satellited and 1

pair of secondarily constricted chromosomes were noticed in the present study (Figs. 8 and 5a).

4. H. ovalifolius (Forsk.) Vahl

2n=32=E2+G24+I6

In contrast to the earlier reports, the present study show n=16 and 2n=32

chromosomes in the taxon analysed (Table 1). This is the first report of detailed

karyomorphological study for the species. The somatic complement has 12 pairs 1981 Cytotaxonomy of Malvaceae II 155

(G-type) of chromosomes with nearly median centromeres and 4 pairs (E and I types) with nearly submedian centromeres. No chromosomes with secondary

constrictions or satellites were observed (Figs. 2 and 2a). Chromosomes are

medium to short sized, range in length from 3.06ƒÊ to 1.45ƒÊ with a mean length of

2.17ƒÊ.

5. H. caesius Garcke

2n=36=D2+G18+Gs•L2+I12+Is2

No earlier record of the cytological work for the species is mentioned in the

available literature. The chromosome number 2n=36 and n=18 are therefore,

the first reports for the species. The complement contains 11 pairs (D and G

- types) of chromosome with nearly median and 7 pairs (I-type) with nearly sub

median centromeres. One pair (Gs•L-type) has secondary constriction on long arm

and another pair (Is-type) of chromosome has satellites (Figs. 3 and 3a). Chromo-

Figs. 9a-1 la. Idiograms of P. patens, P. zeylanica and M. capitata respectively.

somes are medium to short sized, ranging in length from 3.15ƒÊ to 1.87ƒÊ with a

mean length of 2.41ƒÊ.

Genus-Abelmoschus Medik.

6. A. manihot (Linn.) Medik. 2n=130=F8+G74+Gs•L4+I10+Is•L2+J8+K14+L10

Only chromosome record 2n=66 by Skovsted (1935 Syn. H. manihot) for the

species could be traced in the available literature (Table 1). The detailed cytologi

cal study revealed the chromosome number to be 130 in somatic nucleus and 65

in the generative nucleus. The somatic complement contains 8 pairs (F and J-types)

of chromosomes with median, 46 pairs (G and K-types) with nearly median and 11

pairs (I and L-types) with nearly sub-median centromeres (Figs. 11 and 8a). In all 3 pairs (Gs•L and Is•L-types) of chromosomes have secondary constrictions on long

arms. Chromosomes are short to very short sized, ranging in length from 1.80ƒÊ

to 0.68ƒÊ with a mean length of 1.33ƒÊ.

7. A. angulosus Wight and Arn. 2n=130=F10+G98+Gs2+Gs•L2+I14+Is2+K2 156 Aparna Dasgupta and R. P. Bhatt Cytologia 46

This is the first report of 2n number and karyotype analysis. 130 chromosomes

were observed in the somatic complement. The karyotype analysis reveals the pre

sence of 5 pairs (F-type) of chromosomes with median, 52 pairs (G and K-types)

with nearly median and 8 pairs (I-type) with nearly sub-median centromeres. In

all, one pair (Gs•L-type) of chromosome is with secondary constriction on long arm

and two pairs (Gs and P-types) with satellites (Figs. 10 and 7a). Chromosomes

are short to very short sized, ranging in length from 2.55ƒÊ to 0.94ƒÊ with a mean

length of 1.60ƒÊ.

Genus-Thespesia Soland. ex corr.

8. T. populnea (Linn.) Soland. ex corr.

2n=28=A2+B6+D10+E4+G4+I2

In contrast to the earlier reports the present observations are n=14 and 2n=28

(Table 1) for the species. The somatic complement is seen to consist of 8 pairs

(A, D and G-types) of chromosomes with nearly median and 6 pairs (B, E and I - types) with nearly sub-median centromeres (Figs. 1 and 1a). Within the complement

8 chromosomes are long, 14 are medium and 6 are short in length. They range

from 6.04ƒÊ to 2.55ƒÊ with a mean length of 4.33ƒÊ.

Hazra and Sharma (1971) have reported I pair of chromosome with secondary

constriction in var. I and 2 pairs in var. II. In Youngman's work (1931) as well

as in the present work, chromosomes with secondary constriction are not noticed

(Figs. 1 and 1a) Tribe-Ureneae

Genus-Malachra Linn.

9. M. capitata Linn. 2n=56=G20+I30+Is6

The present report of 2n=56 and n=28 are in line with the previous report

(Table 1). Karyotype analysis of the somatic complement show 10 pairs (G-type) of chromosomes with nearly median and 18 pairs (I-type) with nearly sub-median

centromeres (Figs. 7 and 11a). Chromosomes are short sized, length ranges from

1.96ƒÊ to 1.02ƒÊ with a mean length of 1.37ƒÊ.

Skovsted (1935) has reported two pairs of chromosomes with satellites. Hazra

and Sharma (1971) have reported 2 pairs of chromosomes with secondary constric

tion and 1 pair with satellited in the taxa they have analysed. The present investi

gation of 2 populations show 3 pairs of satellited chromosomes in the somatic com

plement (Figs. 7 and 11 a). Genus-Pavonia Cav.

10. P. zeyanica Cav. 2n=56=D8+E2+G28+Gs2+I16

It is apparent from the available literature that the species has remained un

explored cytologically. The n and 2n numbers recorded are 28 and 56 respectively.

The somatic complement consists of 19 pairs (D and G-types) of chromosomes with

nearly median and 9 pairs (E and I-types) with nearly sub-median centromeres

(Figs. 6 and 10a). Only 1 pair (Gs-type) of chromosome is with satellites. Chro mosomes are medium to short in size, ranging from 3.40ƒÊ to 1.79ƒÊ with a mean

length of 2.56ƒÊ. 1981 Cytotaxonomy of Malvaceae II 157

11. P. patens (Andr.) Chiov.

2n=28=D2+G22+Gs2+I2

In the present work n=14 and 2n=28 are the chromosome numbers recorded

for the species which confirms the earlier report of n=14 by Bates (1967) . The somatic complement contains 13 pairs (D and G-types) of chromosomes with

nearly median and only 1 pair (I-type) with nearly sub-median centromeres. One

pair (Gs-type) is with satellites (Figs. 4 and 9a). Thirteen pairs of short and one

pair of medium chromosomes are present in the complement. They range from 3.23ƒÊ to 1.62ƒÊ with a mean length of 2.27ƒÊ.

Discussion

The observations presented mainly concern the number and morphology of

chromosomes of 5 genera and 11 species. Different primitive basic numbers pro

posed for the family are 7 (Davie 1933); 5, 6 and 7 (Skovsted 1935) and 6 (Menzel 1966, Hazra and Sharma 1971). All the workers are unanimous regarding the

polyphyletic course of evolution of different genera and species within the family. As multiple of 7 is metwith in the majority of the genera of the two tribes studied,

number 7 can be considered more deep seated in the family. It was suggested that

6 can be the basic number (Bhatt and Dasgupta 1976) on the basis of the study of

H. panduraeformis (2n-24). However, a more primitive nature of the karyotype

metwith in Thespesia poplnea having 2n=28 shows that the number 7 can be a base

number and other numbers observed are presumably derived from the basic number 7 though aneuploidy.

Of the two tribes, the tribe Ureneae is very homogenous in having chromosome

numbers which are simple multiple of 7. In contrast to this members of the tribe

Hibisceae, have chromosome numbers, which are multiple of 6, 7, 8 and 13.

Precise determination of TF% (Total form percentage; Huziwara 1958) and

a rm ratios (R1 and R2) of the karyotypes reveals that chromosomes are with median,

nearly median or nearly sub-median types of centromeres only (Table 2). No chro

mosomes with terminal or sub-terminal centromeres are observed. The karyotypes

n general appears more or less symmetrical as the TF% is between 36.89 and 42.75. the absolute symmetry of karyotype is attained, when the TF% is 50, which is not

noticed in the karyotypes studied for the present work.

The degree of symmetry varies with different taxa, that forms the basis for

s pecific distinction. Moreover, on this basis the genus should be considered as a _??_ rimitive or an advanced one, in which speciation thourgh structural changes must

nave taken place.

On the basis of cytological observation the 3 genera and its species of the tribe

Hibisceae studied can be arranged in the following evolutionary sequence.

The genus Thespesia with low chromosome number longer chromosomes and

more or less symmetrical nature of the karyotype indicates a very primitive nature. T he complement of T. populnea contains 28 chromosomes, which is the multiple of 7.

T he chromosomes range from 6.04ƒÊ to 2.55ƒÊ in length with a mean length of 4.33ƒÊ.

The chromosome number recorded for the genus Hibiscus in the present work Table 2. Comparison of the somatic chromosomes of investigated taxa 1981 Cytotaxonomy of Malvaceae II 159 as well as in the earlier investigations (viz. Davie 1933, Skovsted 1935, 1941, Mad vedeva 1936, Nakajima 1936, Rao 1941, Menzel and Wilson 1961, 1963, Sharma and Sharma 1962, Hazra and Sharma 1971, Kachecheba 1972) show a wide range from 2n=22 to 2n=225. Among the species investigated presently the lowest number 2n=32 in H. ovalifolius and the highest number 2n=120 in H. mutabilis are recorded. Passing from more primitive to more advanced, the different species of Hibiscus under consideration may be placed in the following sequence (Table 2), H. ovalifolius, H. caesius, H. trionum, H. hirtus and H. mutabilis (Figs. 2a-6a). It is quite evident that different levels of ploidy accompanied by structural alterations in chromosomes might have played a significant role in the speciation of the genus Hibiscus. Between the two species of the genus Abelmoschus studied A. manihot shows evolved nature of the karyotype as compared to that of A. angulosus (Figs. 7a and 8a). Cytological work of different genera under the tribe Ureneae is done by Sko vsted (1935, 1941), Bates (1967), Kootin-Sanwu (1969), Hazra and Sharma (1971). In the present work as well as in the earlier investigations homogeneity in the chro mosome number is noticed. The 2 species of Pavonia studied show different chromosome numbers viz. 2n=28 in P. patens and 2n=56 in P. zeylanica. The karyotypes of both the species resemble each other in their gross morphology and in having a pair of chromosomes with satellites (Figs. 9a and 10a). P. zeylanica appears more advanced than that of P. patens due to the higher ploidy level and less TF% (39.38-Table 2). The chromosome number of Malachra capitata is 2n=56. As the karyotype has more number of nearly sub-median types, 3 pairs of SATs (Fig. 11a), low TF% (36.89-Table 2) and comparatively shorter chromosomes, the species can be con sidered more evolved than Pavonia. Both the tribes show difference in the chromosome number, morphology and represent primitive to advanced type of karyotypes. Thus, by karyomorphological observations, it is apparent that both these tribes must have diverged very early in the course of evolution. The members of the tribe Ureneae show karyotypes, which are less evolved than those of the tribe Hibisceae, as they have lesser chro mosome numbers in their somatic complements (Viz. 2n=28 and 56). It is pro bable that polyploidy has not played that significant role in the tribe Ureneae as in the case of Hibisceae, in the evolution of various taxa of the tribe.

Summary

Five genera of the family Malvaceae are considered for the present work. On the basis of the cytological work 3 genera of the tribe Hibisceae studied can be ar ranged in the following evolutionary sequence i.e. Thespesia, Hibiscus and Abel moschus. In the tribe Ureneae the studies of two genera show the evolved nature of karyotype of Malachra capitata over Pavonia. The most primitive nature of the karyotype is found in Thespesia populnea having 2n=28 suggest number 7 can be a base numbers. 160 AparnaDasguptaandR. P. Bhatt Cytologia 46

Acknowledgement

The authors are grateful to Professor C. H. Pathak, and Dr. S. D. Sabnis, De partment of Botany, The M. S. University of Baroda, for their constant help during the course of the work.

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* Not consulted in original .