Cytotogia

Irradiation

Studies

on

the

II.

Karyology

Ultraviolet

Y. S. R. K. Sarma Laboratory

Received

October

of

42: 291-295,

1977

Charophyta

light

and

S. B. Singh

of Algal Cytology and Cytogenetics, Department of Botany, Banaras Hindu University, Varanasi-221005, India

18, 1975

The effects of ultraviolet light on green algae have been studied by many work ers interested in different fields but the studies of UV particularly in relation to algal karyology are very few. Cytological studies of UV irradiated chromosomes have been carried out in Prorocentrum micans (Dinophyceae) by Dodge (1964). Chromo some and chromatid exchanges giving rise to anaphase bridges were reported by him. Other UV studies made on Oedogonium cardiacum by Parker and Harsley (1972) and in Chlamydomonas by Davies (1965). Kimball (1966) pertained mainly to radiosensitivity studies in relation to different stages of mitotic cycle. But so far as the authors are aware, the present work is the first study to demonstrate that UV is capable of inducing chromosomal aberrations in charophytes. Material Two and

species

one

mental

in

the

were

same

carefully

water

which

were

charophyte

taxa in

were

were a mixture

terials

were

nique

(Godward

the

ergs/mm2),

24hr

at of

cytologically 1948)

to

different

3:1

absolute studied

throughout

sizes

by

effects

24, and

48, glacial

Godward's course

of

of

of 72

and

taxon pond

23cm

(51 time

3mt

96

materials

irradiation

and

of were The

following

acid. alum

ex

(9.18•~

the

hr

ergs/ of

photoreactivation.

acetic iron

study.

filtered

ergs/mm2),

after

labo

each

the

All

the

further

of

increasing

W.)

experi

environment

of

a distance

medium

the of

alcohol

for

suitable

D.

as to

natural

respectively.

eliminate

employing

brought

5ml

R.

used

medium

(6.12•~103

culture

intervals

at

achieved 2 mt

fresh

A)

Br.)

were

in

containing

ergs/mm2)

the

of

(2537

was

W.)

were

culture

light

(A.

D.

growing

antheridia

doses

to

R. taxa

were

petridishes

UV

(12.24•~103

for fixed

in

flagelliformis em

different they

light,

to

transferred

darkness

antheridia in

4mt

N.

Bruz.

(soil-water)

exposed

(3.06•~103 and

and

of

which

placed

in

methods

ex.

plants in

biphasic

variation

Ag. Ag.

ultraviolet and

then

from 1mt ergs/mm2)

placed

water

with

The

posure

selected

to

opaca

.fibrosa

The

selected

mm2/sec).

(N. (C.

pond

irradiation

were

ation

Nitella Chara

transferred

For

103

of

materials.

ratory and

of

species

and

The

acetocarmine

irradi fixed

ma tech

investigation.

Observations

The karyology of the spermatogenous filaments of N. opaca (n=6), N. flagelli formis (n=9) and C. fibrosa (n=14) was critically examined and the cytological

292

Y. S. R. K. Sarma and S. B. Singh

effects produced ities

in dividing

frequently were

as a result cells

observed

stickiness

and

of UV irradiation

were effects

scored commonly

clumping

were recorded.

at metaphase met

Cytologia

with

of chromosomes

and

The mitotic

anaphase

in all the

at metaphase

at

anaphase,

chro

chromosome

metaphase

formation

chromosomes,

most

degrees,

anaphase

erosion,

breakage

The

to varying and

mosome

abnormal

stages.

taxa,

42

and of

anaphase

ring

bridges,

laggards, unequal separation chromosomes, granulation

of and

vacuolization of interphase nu clei and degenerating nuclei. These

effects

were

those

obtained

with

gamma-rays, illustrated

in

similar X-rays

to and

as described and the preceeding

paper.

The most frequently ob served effects in all the three taxa used for experimental work were stickiness and clumping of chromosomes even in materials exposed to 1mt. Besides, the chromosomes appeared faintly stained with fuzzy outlines. With a dose of 1mt treatment, breakage of chromosomes was observed though infrequently at metaphase and anaphase stages in N. opaca and N. flagelliformis but when the dose was increas ed to 2mt, generally one to two fragments in C. fibrosa and upto three fragments in N. opaca and N. flagelliformis were recorded. It was observed that with the Figs. H1-H3. H1,histogram show ing percentage of affected cells in Nitella opaca subjectedto UV light. H2a histogram showing percentage of affectedcells in Nitellaflagellifor missubjectedto UV light. H3ihisto gram showingpercentageof affected cells in Chara fibrosa subjected to UV light.

1977

Irradiation

Studies

on the Karyology

of Charophyta

II

293

administration of higher dose of 3mt and 4mt more than two fragments were noticed in C. fibrosa and more than three in both the species of Nitella. One the whole the percentage of affected cells scored at metaphase and anaphase at lowest dose of 1mt in N. opaca and N. flagelliformis to be 2.00 to 3.11 and 3.85 to 4,75 respectively, whereas no visible abnormalities were scored in C. fibrosa at the same dose level. However, at higher dose of 4mt the percentage of affected cells in creased to 14.44 to 17.78 in N. opaca 16.47 to 18.38, in Ns flagelliformis and 10.00 to 13.79 in C. fibrosa (cf. H1-H3). Apart from the chromosome fragments, anaphase bridges were also noticed. But the nature and shape of anaphase bridges varied from cell to cell at different doses. Among the anaphase bridges, sticky bridges were generally found at low doses of 1mt and 2mt in all the test materials. But at higher doses of 3mt and 4mt most of the bridges were formed of long continuous strands associated with some fragments. In some cases anaphase bridges were constituted by chains of fragments. Formation of ring chromosomes, though infrequent were also recorded in N. opaca and N. flagelliformis both at metaphase and anaphase stages. The other chromosomal abnormalities which were common in all the taxa were laggards, unequal separation of daughter chromosomes to the two poles, and chromosome erosion. Irradiated samples fixed after 96 hr following irradiation with high dose of 4mt showed very few mitotic figures and the frequency of vacuolated and granu lated interphase nuclei was very high. Most of the nuclei in a degenerating con dition. Discussion

The UV induced qualitative effects on the chromosomes of three charophyte taxa studied here are very much similar to the results obtained with X-rays and gamma-rays (see first paper in the series). Stickiness and clumping of chromosomes were found to be more frequent upto 24hr after irradiation at all doses ranging from 1mt to 4mt. Such types of ab normalities were frequently observed in Wada and Izutsu (1961) in Tradescantia cells, Bajer and Bajer (1961) in Haemanthus endosperm which were again con firmed by the observations of Zirkie, Bloom and Urtz (1956). Similar observations also made by Stadler and Uber (1938), Bloom et al. (1955), Gaulden and Perry (1958), Izutsu (1959) and Takeda and Izutsu (1961) pointed out that stickiness was usually "confined to the irradiated pole side of the chromosomes or those lying near the irradiated areas" in Tradescantia. However, in the present study, stickiness was found to be general along the length of the chromosomes. Chromosome breakages were also observed though infrequently in species of N. opaca and N. flagelliformis at a low dose of 1mt whereas generally one to two rarely three fragments were recorded at a dose of 2mt and more than three at higher dose levels. Sticky bridges were more common in comparison to other types of bridges. At high doses of 3 and 4mt anaphase bridges were made up of long con tinuous strands with some fragments. The three taxa viz. N. opaca, N. flagelli

294

Y. S. R. K. Sarma and S. B. Singh

formis

and

ference

C.

in

scored

it

to

light

UV

may

to to

ergs/cm2,

and

dose

of

were

made

of

2•~103

108

ergs/cm2.

appear

at

of

the

more

or

of

of

effects

with

percentage

of

flagelliformis

were

slight

dif

affected more

of

cells sensitive

dose

of

5•~108

the

observations

of

it

seems

the

earlier the

at to

at

on of

UV

dose

uniform

30 of

Tradescantia on

of

Stad

a

reported

a higher

workers effects

in a dose

observations

who

48%

too

25%. to

Similar

Tradescantia

and

that

were

chromosomes

Tradescantia

deficiency.

in

ergs/cm2

of

it increased of

of

Tradescantia

abnormalities

ergs/cm2,

(1957)

0.52•~108

shattering

endosperms

Criag

of fragments

chromosomal

11.6•}1.6%

study,

chromosomes chromosome

reported

cent

and of

tube

per

scored

a dose

less

N.

ergs/mm2

subjecting

the

type

basis

pollen

(1953)

a higher

present

similar the and

2.5•~103

one

Smith

From

basis

of

after

Kirby,

cells

when

of

ergs/mm2,

by

abnormal

the

at

(1942)

opaca

Lovelace

extent

but

Uber

N.

that

a dose

scored. the

less On

42

C. fibrosa.

noticed

be

or

cells.

that to

with

Tradescantia

ler

concluded

(1964)

numerous

more

affected

compard

irradiated

5•~106

showed of

be as

Bailey were

fibrosa

percentage

Cytologia

1.18•~ and

charophyte

on taxa

similar.

Summary The N.

experimental

opaca,

district. to

tative A and less

N.

flagelliformis

The

exposure

12.24•~103

titatively

changes

were

similar

on

were

very

charophyte

radioresponse

similar

to

those

UV

recorded

in

local

to

4mt

each

and

anaphase with

on the

light

under

found

effects

UV

from 1mt

metaphase

chromosomal taxa

to

from effects

at

to

collected

ranged

cytological

much of

subjected

fibrosa,

UV

estimated

assessment

those

C.

of The

qualitatively

comparative

that

and time

ergs/mm2).

and

of

materials

antheridium

ponds

of

(3.06•~103

stages.

X-rays

study

and by

of

Varanasi ergs/mm2

experiment

Tradescentia present

are

were

quan

The

quali

gamma-rays. earlier

revealed

workers more

or

light.

Acknowledgements

of

The

authors

wish

Botany

for

providing

to the second

author

to express

their

laboratory

by the

gratitude

facilities.

authorities

of Banaras

to the The

Head

financial Hindu

of the

Department

assistance

University

provided

is also

grate

fully acknowledged.

Literature

cited

Bajer, A. and Mole-Bajer, J. 1961. UV microbeam irradiation of chromosomes during mitosis in endosperm. Exp. Cell Res. 25: 251-267. Bailey, P. C. 1964. A comparison of X-rays and UV induced aberrations in pollen tube chromo somes of Tradescantia I. Dose curve response to varying moisture conditions. Rad. Bot. 4: 115-119. Bloom, W. and Leider, R. J. 1955. Changes in refractive index of chromosomes by UV or proton microbeam irradiation. Rad. Res. 3: 214-215. Davies, D. R. 1964. Repair mechanism and variations in UV sensitivity within the cell cycle. Mut. Res. 2: 477-486.

1977

Irradiation

Studies on the Karyology

of Charophyta

II

295

Dodge, J. D, 1964. Effects of UV light on the survival and nuclear division of a dinoflagellate . Protoplasma 59: 485-493. Gaulden, M. E. and Perry, R. P. 1958. Influence of the nucleolus on mitosis as revealed by UV microbeam irradiation. Proc. Nat. Acad. Sc. 44: 553-559. Godward, M. B. E. 1948. The iron alum acetocarmine method for algae. Nature (London). 161: 203. Izutsu, K. 1959. Irradiation of parts of single mitotic apparatus in grasshopper spermatocytes with an ultraviolet microbeams. Mie Medical Jour. 9: 15-29. Kimball, R. F. 1966. A repair premutational damage in L. G. Augen Stein, Ronald Mason and Max Zella (Eds). Advances in Radiation Biology, Acad. Press, New York. 2:135-166. Kirby, Smith, J. S. and Criag, D. L. 1957. The induction of chromosome aberrations in Tradescan tia by UV radiation. Genetics 42: 176-187. Lovelace, R. 1954. Chromosome shattering by UV radiation (2650 A). Proc. Nat. Acad. Sc. 40: 1129-1135. Parker, K. E. and Horsley, R. J. 1972. The UV radiosensitivity of Oedogonium cardiacum cells at various stages of the cell cycle. Rad. Bot. 12: 239-248. Sarma, Y. S. R. K. and Singh, S. B. 1977, Irradiation studies on the karyology of Charophyta I. X-Rays and gamma-rays. Cytologia 42: 279-290. Stadler, L. J. and Uber, F. 1938. Genetic effects of UV light on maize. Genetics 23: 171. - and 1942. Comparison of genetic effects of different wavelength of UV light on maize. Genetics 27: 84. Takeda, S. and Izutsu, K. 1961. Effect of UV microbeam irradiation upon cell division. Jap. J. Genetics 36: Supl. 1: 105-114. Wada, Bungo and Izutsu, K. 1961. Effects of UV microbeam irradiations on mitosis studied in Tradescantia cells in vivo. Cytologia 26: 480-491. Zirkle, R. E., Bloom, W. and Uretz, R. B. 1956. Proc. Int. Conf. Peaceful Uses of Atomic Energy. Geneva 1955. 11: 273.

Irradiation studies on the karyology of Charophyta. II. Ultraviolet light.

Cytotogia Irradiation Studies on the II. Karyology Ultraviolet Y. S. R. K. Sarma Laboratory Received October of 42: 291-295, 1977 Charop...
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