ABOUT CYTOGENETIC MECHANISM OF CHEMICAL MUTAGENESIS - Ecological Consequences of Increasing Crop Productivity - page 261

storage), and July (11 months of storage). Distilled water was used both in the control
and experiments. Chromosome rearrangements were analyzed in plantlets (meristem
of tip roots).
In control and experiments, we used distilled water.
A total of 100 seeds were treated in an aqueous solution of phosphemid in the fol-
lowing concentrations: 1 × 10 −2 M (22.4 mg was dissolved in 10 ml water), 2 × 10 −2 M
(22.4 mg was dissolved in 50 ml), or 2 × 10 −3 M (2.24 mg dissolved in 50 ml of water).
The treatment was carried out at room temperature (19-21°C) during 3 h. Then, seeds,
which were treated by the mutagen, were washed in running water. The washed seeds
were placed in Petri dishes on fi lter paper moistened with the solution of colchicine
(0.01%). Seeds germinated in a thermostat at 25 °C, but in July 1968 because of the
hot weather, the temperature in the thermostat could reach 27 °C. In parallel control
experiments, the seeds were treated with aqua distillate.
After 24, 27, 31, and 36 h after soaking of seeds, we selected plantlets, took away
plantlets not longer than 1 mm, and named them plantlets. The term plantlet refers to
those plantlets that emerge after the beginning of soaking of dry seeds. These plantlets
were placed in a Petri dish for further germination and subsequent fi xation.
Root tips were cut off with a razor and placed in the following solution: 96 per-
cent ethanol 3 parts + 1 part of glacial acetic acid. Solution was poured out after 3—4
h. Plantlets were washed for 45 min in 70 percent alcohol for keeping. We prepared
temporary pressure preparations: fi xed root tips were stained by acetous carmine and
crushed in a solution of chloral hydrate between the slide and cover slip. We ana-
lyzed chromosome aberrations in metaphase plates of plantlets in the fi rst division
after treatment of seeds (2 n -karyotype). In each plantlet, all metaphases were counted.
Intact seeds of yields of 1966, 1067, and 1969 were used as control. These plantlets
were fi xed at different time intervals from 3 to 24 h.
Mitotic activity in the plantlets was detected on metaphase plates, depending on
the number of nuclei in plantlets in the control and experiment. We used the plantlets
in different intervals of time after the plantlet. In each plantlet, we counted between
500 and 1000 nuclei. We calculated the ratio of amount of plantlets with metaphase to
all observed plantlets at all stages of fi xation.
In all experiments, standard deviation from the mean was estimated.
In experiments with irradiation, seeds were exposed to X-rays in doses of 3,000;
2,000; and 4,000 R. Plantlets were selected for further germination for 22, 24, and 27
h after their soakage, fi xed them, and the preparations were made, as described above,
0, 2, 3, 6, and 9 h after appear of plantlets. Control tests were performed in parallel and
their results were combined.
24.4 RESULTS AND DISCUSSION
Radiation treatment by X-rays in the doses of 2000 and 3000 R evoked high percent of
rearrangements of chromosomes in the early plantlets (Table 24.1).