Effects of prolonged exposure to space flight factors for 175 days on lettuce seeds

73—1177/81/0401—0083$05.OO/0

8385. COSPAR, 1981. Printed in Great Britain.

Adv. Space Res. Vol.1, pp.

EFFECTS OF PROLONGED EXPOSURE TO SPACE FLIGHT FACTORS FOR 175 DAYS ON LETTUCE SEEDS L.V. Nevzgodina, E.N. Maximova and Yu. A. Akatov Institute of Medical and Biological Problems, Moscow, USSR

ABSTRLCT We have studied the effects of prolonged (up to 175 days) exposure of Lactuca sativa seeds to space flight factors, including primar~y cosmic radiation heavy ions. The data obtained evidence a significant fourfold increase of spontaneous mutagenesia in seeds both with regard to the tote]. number of aberrant cells as well as the. formation of single cells with multiple aberrations. Comparison of the present experiment with earlier works shows that the frequency of such aberrations increases with the duration of the flight. INTRODUCTION During the 1979 expedition aboard the orbital station Salyut 6 the experiment Biobloc—3M was performed. The influence of space flight factors on air—dried lettuce (Lactuca sativa) seeds under the conditions of prolonged exposure aboard the station was studied. Due to the low level of metabolic activity in the resting state, exposed biological objects were able to accumulate, over long time periods, the modifications induced at the cellular level by spaceflight. PROCEDURE Air—dried Lactuca sativa seeds, in plastic pockets, were placed in unsealed packs together with integral dose detectors • The packs were delivered to orbit by the transport spaceship Soyaz 32, launched on 25 February 1979, and transferred by the crew on board, the station Salyut 6 immediately after docking. During the 175 day expedition period the packs with the biological objects remained in a fixed position in the spaceship. At the expedition’s end the packs were returned to Earth aboard the transport spaceship Soyuz 34, landing on 19 .Angust 1979. The total dose recorded by thermoluminescent dosimeters was 3.7 rad. ~wniii*tion of the biological objects began two weeks after landing. The following parameters were studied: the number of aberrant cells, the number of single and multiple aberrations, and the number of dividing cells at the anaphase and telophase stage per rootlet. 83

L.V. Nevzgodina et al.

84

RESULTS The results of the cytogenetic analysis of Lactuca sativa seed cells In the flight and control groups are presented In Table 1. TABLE I

Frequency of Aberrant Cells In Seedlings of Lettuce Seeds Exposed Aboard The Orbital Station Salyut 6

Group Parameter

__________________________________ Control (spontaneous mutations)

Number of ama— and telophase cells eYeinined Number of rootlets examined Mean number of aim- and telophase cells per rootlet Total number of aberrant cells

Flight

5059

8185

46

101

110

81

39

288

Percent of aberrant cells

0.77 ±0.12

Number of multiple aberrations

0

Percent of multiple aberrations

0

0.28

Mean number of aberrations

1.00

1.10

3.52

±0.20

23

±0.06

per aberrant cell An inhibition of the mitotic cycle Is evidenced by a lower number of ama— and telopb.ase cells per rootlet In the flight matérial as compared with the control, 81 and 110 respectively. The number of aberient cells in seeds exposed aboard the station was four times higher then in the control: 3.52 ±0.2 % and 0.71 ±0.12 %, respectively-. Moreover, in the flight group 23 cells with multiple aberrations have been found in 101 seeds studied. Control seeds never shored such multiple aberrations • In the previoits experiments aboard the biosatellites Cosmos 368, Cosmos 782, and Cosmos 936 and orbital station Salynt, enhancement of the number of aberrant cells and cells w~.thmultiple aberrations was also observed in the flight groups /1, 2, 3, 4.1. In comparing (Table 2) the results of the above experiments and the present experiment abøard Saly-ut 6, the percentage of aberrant cells and the percentage of cells with multiple aberrations increases with the duration of the flight.

Prolonged Space Flight Effects on Lettuce Seeds

TABLE 2

Frequency of Aberrant Cells in Seedlings from Exposed Lactuca sativa Seeds Versus The Duration of Exposure

Flight Fluence of heavy Frequency of aberrant cells, duration, ions (Z~6,LET~ days 200 keVpm~), ions cm Single aber— Multiple

Flight

rations less spontaneous mutation

aberrations

not measured

1.06

0.16 ~ 0.09

1.45 ±0.30

0.13

2.40

±0.32

0.18

2.00

+

Cosmos 368

7

Cosmos 782

20

5.0 ~ 0.3

Cosmos 936

20

2.6

Salyixt

73

not measured

Salyut 6

85

175

6.3

—

33.6

(~0.3)

±3.5

+

0.24

±0.09 ±0.09

0.28

0.21 ±0.09

2.75 ~ 0.17

0.28 ~ 0.06

DISCtJSSI(~ One may suppose that frequency of multiple aberrations Is correlated with the fluence of hea’vy- Ions. Such a conjecture is confirmed by the res~lts of similar experiments with seeds directly hit by heavy ions [31. However, new experiments are necessary in order to give a quantitative interpretation of this effect. The data obtained confirm that air—dried lettuce seeds present a convenient biological model for monitoring space flight factors over time periods up to 175 days. A longer éx~osure results in a higher number of aberrant cells and cells with multiple aberrations. ~NC~ 1.

T. Gaubin, N. N. Kovalev, H. Planel, L. V. Nevzgodina, G. Gusset and B. Pianezzi, Aviation Space and Environmental Medicine ~Q, ~ 2, 134. (1979J.

2.

L. V. Nevzgodina, Tn. G. Grigoriev, N. M. Papy-an, I. S. Skukina and In. V. Farber, Space Research XI,111 (1973).

3.

Tu. G. Grigorlev and L. V. Nevzgodina, in: Edvance o~Space

Biophysics, 4-.

Pushobino,

1978,

p. 52.

Tn. V. Farber, L. V. Nevzgodina, N. M. Papyan and T. P. Soboleva, Kosm. Biol. I Med. 6, 24 (1971).