Obtaining Twin Plants In Dahlias

G. I. Rodionenko and E. I. Zaar

This article was originally published in Russian in Priroda in 1951. It is presented here as part of the Dahlia Archive, with images of the original article included for reference.

The English translation was prepared with AI assistance and reviewed against the original Russian text. As with any historical translation, especially from a technical article of this period, some wording reflects editorial judgment rather than a one-to-one rendering of Russian syntax.

This article is believed to be in the public domain. It is reproduced here on The Dahlia Archive for historical and educational purposes.

Russian:
Родионенко, Г. И. и Заар, Э. И. Получение растений-близнецов у георгин. Природа, 1951, № 5, с. 62–63.

English:
Rodionenko, G. I., & Zaar, E. I. “Obtaining Twin Plants in Dahlias.” Priroda, 1951, no. 5, pp. 62–63.

In experimental work involving the directed alteration of plant nature, the need often arises to have two plants from a single seed while still in the cotyledon stage of development, one of which can later serve the researcher as a control.

For large seeds, for example in plants of the legume family, cases are known in which two plants have been obtained from one seed by dividing it during germination (M. A. Nikonenko, "Twin Plants," Yarovizatsiya, No. 6, p. 107, 1940).

For an experiment studying the influence of external conditions on the double-flowered nature of dahlia inflorescences, we needed to have starting plants that were identical in hereditary terms at an early stage of development.

The seeds of dwarf dahlias used for the experiment are considerably smaller than the seeds of Gleditsia, with which M. A. Nikonenko worked. In addition, the cotyledons of dahlias do not possess a large reserve of nutritive substances.

The technique for obtaining twin dahlia plants consisted of the following. The seeds were germinated on moist filter paper. From a seed that had begun to germinate, the outer coat was carefully removed with forceps. When selecting germinated seeds for cutting, it is very important that the length of the emerging root not exceed 0.2–0.5 cm.

A safety-razor blade, previously rinsed with alcohol, was used to cut the seed. Experience showed that it is better to make the cut by dividing the seed between the cotyledons. In this case, the wounded area is considerably smaller and is quickly covered with callus.

The halves cut in this way are placed in rows, cut side upward, on filter paper lowered into water slightly colored with potassium permanganate.

Figure 1 

General view of a crystallizing dish with seeds cut into halves: 1 — reflector; 2 — glass; 3 — seed "halves"; 4 — small plate; 5 — cork; 6 — filter paper.

Figure 2

a — seed before cutting; b — after cutting; c — development of the growing point and root in the “twins.”

In our experiment, the seed halves were placed in the crystallizing dish until callus had formed at the cut site and roots and shoots had developed (Fig. 1). The temperature in the crystallizing dish was 16–18°C; when the electric lamp was switched on, it rose to 25°C, which accelerated the development of the shoot and root from the callus. The electric lamp remained switched on for 14–16 hours per day.

Under the influence of light (with a 40-watt electric lamp serving as an additional light source), the surface of the cotyledons began to turn green as early as the second day after cutting. On the 3rd–4th day, swellings visible to the naked eye appeared at the cut sites—callus. From these calluses, the growing point and root later formed (Fig. 2), and in individual cases, 2–3 shoots developed at once from a single callus at the cut site.

After one and a half to two weeks, the plants were suitable for transplanting into the soil of a hotbed or into pots for greenhouse culture.

The experiment with seed halves was begun on February 15. The twin plants were planted outdoors on May 14. The experiment was completely successful. By the end of summer, we had 50 pairs of dahlia plants grown from seed halves. The plants developed quite normally.