II. 31. Effect of aeration during sodium azide treatment of barley seeds on the physiological damage in M1 seedlings.
J.L. Molina-Cano, La Cruz del Campo S.A., Malting and Brewing Company, Apartado 53, Savilla, Spain. "R"
Oxygen is known to be a major modifying factor of biological, including genetic, damage induced by radiations in seeds (Conger et al., 1977). On the other hand, the mutagenic action of sodium azide was tentatively related to its character as a respiratory inhibitor and hence to oxygen, although the exact mode of action of the mutagen has not yet been elucidated (Nilan et al., 1976). Several workers; e.g., Walther (1976), Konzak (1977), have suggested using aerated solutions of N3 Na during the mutagenic treatment, but the effect of anoxia in the subsequent M1 plant injury has not been measured. This effect, measured as M1 plant height and survival, is very important because of its known correlation with M1 mutation frequency (Gaul, 1959).
To study the modifying effect of oxygen during mutagenic treatment with sodium azide, an experiment arranged in randomized blocks with four replications was laid out. Twelve lots each of 50 seeds of Trumpf barley were prepared by screening a 100 g. sample over a 2.5 mm. sieve and dividing it by using a Boerner sample divider. The samples were soaked - using separate flasks - in distilled water for 15 hours at 2°C, then transferred to oxygenated distilled water for 4 hours at room temperature. Each four of them were then randomly allotted to one of the following treatments:
1. Air bubbled phosphate buffer at pH 3.
2. Air bubbled 10-3 M sodium azide solution in phosphate
buffer at pH 3.
3. 10-3 M sodium azide solution in phosphate buffer at pH
3 without bubbling.
The duration of all three treatments was 2 hours at room temperature. After that the seeds were rinsed six times in deionized water and 39 of them from each treatment were sown in moist vermiculite. Each block consisted of a 41 cm x 48 cm plastic tray filled with moist vermiculite 5 cm deep, in which the three treatments were arranged at random. Each treatment was represented in each block by a 3 row plot - distance between rows 5 cm, distance between seeds with a row 3 cm. They were grown under continuous light - Osram HQLS 80 W lamps located 80 cm above the trays - and a temperature of about 25°C, and were supplied with nutritive solution by capillarity following heading.
Two measures were recorded when the first leaf ceased to grow:
a) Length of the first leaf of all surviving plants. b) Number of surviving
plants per treatment.
The averages are presented in Tables 1 and 2. The anaylses of variance of these data are presented in Tables 3 and 4, and the individual contrasts, according to Dixon and Massey (1969), in Tables 5 and 6. From all that body of data it may be concluded:
a) Sodium azide itself induced a nearly null physiological damage.
b) Anoxia had a very strong modifying effect which was expressed by an increase of mortality and a decrease in leaf length. It should be pointed out that the leaf length decrease was highly significant (Table 5) and the increase in mortality was not (Table 6) but its confidence interval was strongly skewed to the right.
These results were confirmed in the field because the M1 plants coming from treatment C were suffering strong stunting, stripping and flecking, and only 35% of them set seed.
Table 1. Average length of 1st leaf (cm)
Table 2. Number of non-germinating seeds (mortality)
Table 3. Analysis of variance (1st leaf length)
Table 4. Analysis of variance (mortality)
Table 5. Individual contrasts (1st leaf length)
Table 6. Individual contrasts (mortality)
References:
Conger, B.V., C.F. Konzak and R.A. Nilan. 1977. Radiation sensitivity and modifying factors. In Manual on Mutation Breeding, 2nd edition, IAEA, Vienna. pp. 40.
Dixon, W.J. and F.J. Massey. 1969. Introduction to statistical analysis. 3rd edition, Mc-Graw Hill. pp. 163
Gaul. H. 1959. Determination of the suitable radiation dose in mutation experiments. Proc. 2nd Eucarpia Congress. Koln. pp. 65-69.
Konzak, C.F. 1977. Azide treatment of cereal seeds. In Manual on Mutation Breeding. 2nd edition, IAEA, Vienna. pp. 79-80.
Nilan, R.A., A. Kleinhofs and C. Sander. 1976. Azide mutagenesis in barley. In Barley Genetics III. Ed. H. Gaul. Verlag Karl Thiemig, Munich. pp. 113-122.
Walther, F. 1976. The influence of storage on sodium azide treated barley seeds and on the efficiency of the chemomutagen. In Barley Genetics III. Ed. H. Gaul., Verlga Karl Thiemig, Munich. pp. 123-131.
