Cytologia 49: 781-787, 1984

New Basic Chromosome Numbers and Cytology for Some Scrophulariacious Weeds of Bihar (India)

A. R. P. Sinha

Department of Botany , Govt. College, Port Blair-744 104, India

Received February 9, 1983

Cytologically the taxa of the family Scrophulariaceae is poorly known . Only a few taxa having ornamental or economic importance have been investigated cytologically in detail. In the present investigation chromosome number for five weeds are reported for the first time and new chromosome numbers for two species of the same genus are reported. All the taxa under investigation are important weeds, mainly growing in the paddy fields of Bihar (India). A detailed cytology of the species has been observed and discussed.

Materials and methods

All the plants for which chromosome counts are reported here were collected from different paddy fileds as well as from grassland as mentioned in Table 1. Flower buds were collected at random from natural populations. Fixation of flower buds thus collected was made in Carnoy's fixative between 8AM and 10AM. A few drops of ferric chloride were added in the fixative as a mordant to obtain good staining of the chromosomes.

All the stages of meiosis were obtained by squashing anthers in 2 per cent acetocarmine. Photomicrographs were taken from temporary slides.

Voucher specimens of all the plants taken for the present investigation have been deposited in the Herbarium of the Department of Botany, Magadh University, Bodhy-Gaya (India).

Table 2 summarises the result of cytological observations on seven weeds belonging to five genera. Details of morphological and cytological observations of the weeds are the following.

All the weeds undertaken for present investigation are annual and grow mainly in paddy fields of different localities as mentioned in Table 1. There is not much morphological variation between the plants of different localities except in Lindernia crustacea where there is much differences between the plants of Lc 0977, Lc 2077

population and the plants of Lc 0778 population. Measurements for the chraracters have been made in 20 plants selected at random for each of the populations growing in different localities. Plants of the population Lc 0977 and Lc 2077 were 6 to 7.5cm in height, average length of the leaf was about 1.7cm and breadth 1.2cm; internodes about 0.8 to 1.4cm long, branches were 3 to 5 per plant. In contrast to these, the plants of population Lc 0778 were 17 to 19cm in height; the average

782 A. R. P. Sinha Cytologia 49

Table 1. List of materials with locality and period of their collection

Table 2. Chromosome number, percentage of pollen size variation and percentage of sterile pollen

(See Table 1 for species names of the populations)

* Indicate first report of chromosome counts .+ Indicate new base number .a Raghavan and Srinivasan (1940).b Biswas (1975).c

Bhattacharyya (1968).

1984 Cytology for Some Scrophulariacious Weeds of Bihar (India) 783

length of leaf was about 2.3cm and breadth 1.6cm; internodes were about 1.5 to 1.8cm long; branches were 6 to 7 per plant.

In most of the cases, the plants flower over a long period , extending from July to March, but Centranthera tranquobarica flower only between September and November, and Sutera dissecta has been seen in flowering condition from November to April.

Detailed meiotic studies have been made in plants of all the populations mentioned in Table 1, and gametic chromosome numbers as listed in Table 2 have been confirmed for all the weeds (Figs. 1 to 5, 10, 11, 13, to 20).

Mitotic studies have been made in Lindernia crustacea and Lindernia multiffora. The somatic chromosome number has been determined to be 2n=4x=28 in Lin

dernia crustacea (Lc 0977) and 2n=2x=14 in Lindernia multiflora (Lm 0877).Meiotic division in general was found to be non-synchronized, different stages

of division right from pachytene to anaphase II being present in the same anther squash.

In Centranthera tranquobarica, Dopatrium junceum, Lindernia multiflora and Lindernia viscosa multivalents were observed frequently at diakinesis and metaphase I, but no multivalent was seen in Limnophila indica and Sutera dissecta. In Lindernia crustacea multivalent was seen in its cytotype with chromosome number n=21 but found absent in the cytotype with n=14. In addition to multivalent formation secondary association of chromosomes was frequently seen in these plants. But frequency was more in Dopatrium junceum.

Univalent formation, clumping and precocious separation of chromosome were observed in about 15 to 30 percent of the pollen mother cells at diakinesis and metaphase I. Clumping and stickiness of chromosome was more pronounced in

Centranthera tranquobarica and Lindernia multiflora.A peculiar and interesting phenomenon of fusion of two PMCs was noticed

commonly in Dopatrium junceum (Figs. 7 and 8). Presence of laggards, simple bridges and unequal separation of chromosomes to the poles at anaphase I and It was also recorded (Figs. 6 and 12). In addition, the phenomenon of cytomixis was observed at various stages of division (Figs. 2, 9 and 21).

In almost all the weeds studied except Lindernia crustacea and Sutera dissecta,

pollen grains were found to be of variable size. Varying percentage of micropollen, giant pollen and sterile pollen were recorded from population to population (Table 2).

Discussion

Meiotic studies of seven species belonging to five genera of the family Scro

phulariaceae have been done for the first time.Non-synchronization of the meiotic phases has been observed frequently in

most of the plants in question. This indicates that this is a common phenomenon. Non-synchronization of meiosis in the Scrophulariaceae has been reported by some earlier workers as well. Frankel (1940) has attempted to co-relate the phenomenon with male sterility along with other kinds of meiotic irregularities in Hebe townsonii.

784 A. R. P. Sinha Cytologia 49

Figs. 1-11. 1, Centranthera tranquoharica. Metaphase showing 13 bivalents and one quadrivalent.

2, cytomixis between 4 PMCs at tetrad. 3-9, Dopatrium junceum. 3-4, diakinesis and metaphase

showing 14 bivalents. 5, anaphase I showing 14 chromosomes at each pole. 6, anaphase I with

laggards. 7-8, two PMCs in process of fusing with each other. 9, cytomixis between 2 PMCs

at anaphase II. 10-11, Limnophila indica. 10, diakinesis showing 16 bivalents. 11, anaphase I

showing equal separation of chromosomes. All•~750.

1984 Cytology for Some Scrophulariacious Weeds of Bihar (India) 785

This was regarded as an effect of a male sterility gene. In Russelia, on the other hand, Pal (1961) did not find any such correlation between pollen sterilty and nonsynchronization. In present case, non-synchronization along with other meiotic irregularities leading to some degree of pollen sterility has been found. This supports the correlation theory to some extent.

Figs. 12-21. 12-13: Limnophila indica. 12, anaphase I with laggards. 13, anaphase II showing

equal separation. 14-15, Lindernia crustacea. Diakinesis and metaphase showing 14 bivalents.

16, anaphase I showing equal separation. 17, L. multiflora. metaphas showing 7 bivalents. 18,

L. viscosa. Metaphase showing 10 bivalents. 19-21, Sutera dissecta. 19, metaphase showing 12

bivalents. 20, anaphase I showing equal separation. 21, cytomixis between 2 PMCs at meta

phase through a prominent cytoplasmic tube. All•~750.

Presence of one or more multivalents in Centranthera tranquobarica, Dopatrium

junceum, Lindernia multiflora, and L. viscosa suggests that some chromosomes are represented more than twice in their complements and lend support that these species are polyploids. In case of Limnophila indica and Sutera dissecta multi

786 A. R. P. Sinha Cytologia 49

valents were absent. Still interesting is the case of Lindernia crustacea. Multivalents were observed in tis cytotype with the chromosome number n=21, but these were found absent in the cytotype with n=14. This may be attributed to some "special genotypically controlled tendency to bivalent formation" in polyploids as

found by Muntzing and Prakken (1940) in Phleum twins, Riley and Chapman

(1958) in wheat and Khoshoo (1960) in Sisymbrium irio. Equally surprising is the presence of multivalents in Lindernia multiflora (n=7). Translocation may be responsible for this situation. High pollen sterility in them gives some support to this idea.

Appearance of univalents may be attributed to the precocious disjunction of chromosomes. Powell (1968) has recorded an instance of origin of univalents as a result of precocious separation of chromosomes in some species of Perityle (Com

positae).Clumping and stickiness of chromosomes, at metaphase I and anaphase I and

II were common phenomenon among the weeds undertaken for the present investi

gation. But this phenomenon was found to be more acute in Centranthera tranquobarica and Lindernia multiflora. This anomaly may be due to some environmental as well as physiological conditions. Clumping and stickiness of chromosomes have been observed more frequently in case of Gamma-ray irradiated plants (Sudhakaran 1972), chemically treated plants (Mehra and Mann 1974) and UV irradiated

plants (Sarma and Singh 1977). In nature high temperature and cosmic irradiation are mainly responsible for the phenomenon.

Other anomaly is secondary association of bivalents at metaphase I. This is regarded as an indication of polyploidy and further proves the polyploid origin of most of the Scrophulariaceae weeds. Pal and Pal (1971) working on Lindenbergia indica and Mazus japonicus have also supported this view.

The phenomenon of cytomixis and fusion of two PMCs are being discussed in detail in two separate papers.

Variable size of pollen grains and various degree of pollen sterility as mentioned in Table 2 are outcome of the meiotic irregularities already discussed above.

Acknowledgement

I acknowledge my deep sense of gratitude and reverence to Late Prof. V . Thakur, the then University Professor and Head of the Department of Botany , Magadh University, Bodh-Gaya, for his consistent guidance throughout the course of the

present investigation. I am thankful to U. G. C. for financial assistance through F. I. P.

Abstract

New chromosome numbers and detailed cytology for seven weeds (Scrophulariaceae) from Bihar are reported here. First counts are reported for five species belonging to five different genera Centranthera tranquobarica n=15 , Dopatrium junceum n=14, Limnophila indica n=16, Lindernia viscosa n=10 and Suterad issecta

1984 Cytology for Some Scrophulariacious Weeds of Bihar (India) 787

n=12 and new numbers are also reported for two species of one genus Lindernia i.e. Lindernia crustacea n=14 and Lindernia multiflora n=7 . Meiosis in general was non-synchronized. And anomalies like univalent and multivalent formation

, secondary association of chromosomes etc , have been observed in some pollen mother cells (PMCs) at metaphase 1. In most of the weeds pollen grains were found to be of variable size.

References

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