Glossary:
Initial cells - the cells of meristem.
Cambium - a group of initial cells forming a circle in the center of the stem (meristem).
Meristem -a formative plant tissue usually made up of small cells capable of dividing indefinitely and giving rise to similar cells or to cells that differentiate to produce the definitive tissues and organs.
Mutation - a sudden change in hereditary material responsible for keeping genetic information and its transmission from cell to cell and from descendant to descendant.
Parenchyma - a tissue of higher plants that consists of thin-walled living cells forming polyhedrons of more or less equal sizes in all the directions.
Plastids - any of various cytoplasmic organelles of photosynthetic cells forming a complicated system of inner membranes and fulfilling different functions.
Nucleous DNA (chromosomes) - deoxyribonucleic acids of the nucleus of the cell

Sowing of March, 1997 did not differ from other sowings. For instance, the seeds of Weingartia lanata cv. Endorama got from V.Romanov (Rostov-on-Don) germinated on the 3rd day. The seedlings were of ordinary coloring and grew well. I had about 100 of them.

photo 1. The implantation of the "snowy" shoot of Weingartia lanata cv. Endorama succeeded in spite of its small size. Soon it began to develop thorns of more or less normal size. But its color began to change from "snowy" to pale yellow without any green at all though

By July 2000 they needed badly another singling - the forth. The seedlings were rather big and grew very close to one another. I postponed the singling during a year. One day a friend of mine dropped to my place and asked for a seedling of Weingartia lanata. I hardly squeezed the tweezers through the thorns. With great difficulty, in spite of mellow substratum, I managed to pick up a random seedling. At the free space I noted something white. Amazed I stared at it to find a snow-white shoot with tiny thorns of the neighbor seedling. I cut carefully this miracle that grew in the full darkness. I was still more amazed when I found at the basis of the stem pale-green spots. I wished I could keep this part of the stem uncut for the implanting. During the implanting to the short (3 cm high) Trichocereus sp. I found still paler green spots on the shoot near the cambial circle. That means a part of tissues containing chlorophyll remained inside the grafter. I was glad.

The color of old and new thorns did not differ at all. All of them unlike at other seedlings of Weingartia lanata were white without dark tips.

All the mentioned features are still without changes though the plant is kept without any shade at the south balcony. Meanwhile, the 3 year old plant that gave a "colored" shoot gave other two, unfortunately green.

In the case of Weingartia lanata cv. Endorama the mutation of most plastids took place, a part of initial cells of cambium kept chloroplasts that is why there is parenchyma containing chlorophyll in some parts of the stem. Kernel DNA are unlikely to mutate, so, the "colored" Weingartia will give seeds which will give rise only to the green seedlings. This form can be reproduced only by implanting shoots (by vegetable way)

photo 2. The seeds of Gymnocalycium not germinated by the beginning of the experiment gave seedlings of absolutely typical coloring. As for "colored" plants Gymnocalycium ritterianum P219 (photo 2) has pink-brown epidermis

In the sowing of spring 2000 I had 5 kinds of seeds of Gymnocalycium. I decided to experiment with them using UV rays. The irradiation took place the third day after the sowing of the seeds. The distance from the quartz lamp to the soil was not more than 16 cm. The irradiation lasted 15 minutes. By the moment of irradiation the skin of some seeds had already burst. Further these seeds gave "colored" seedlings. Unfortunately I could not examine every seed and can not say how many seeds had burst skin by the moment of irradiation and how many of them gave "colored" seedlings. The first signs of the change of the color of epidermis appeared at the first week of their lives.

At the same time of 5 kinds of Gymnocalycium seeds only 3 changed the coloring of epidermis. Two others - Gymnocalycium. micidum P36 and Gymnocalycium ferrari GN95 (Gert Neuhuber) that had burst skin - gave the seedlings of the normal color. That is the seeds of these species did not react to the aggressive influence of UV rays.

photo 3. The seeds of Gymnocalycium not germinated by the beginning of the experiment gave seedlings of absolutely typical coloring. As for "colored" plants Gymnocalycium glaucum VS48 (photo 3) - dark purple.	photo 4. and Gymnocalycium guanchinense cv. Renewal (photo 4) turned to be bi-colored, green and pink (it has two pink spots in different parts of the stem).

All the colored seedlings have been developing on their own roots for three months reflecting the sufficient quantity of chlorophyll in their photosynthesizing tissues.

Glossary:
Recessive gene - a latent gene producing no phenotypic effect when occurring in heterozygous condition with a contrasting allele.
Zygote - a cell formed by the union of two gametes I paid special attention to this sowing as the seeds were the result of crossing Gymnocalycium mihanovichii '=ibotan Nishiki' and Gymnocalycium mihanovichii var. friedrichii 'variegatum'.

photo 5. The seedlings were mostly one-color and only 5% of them were variegated. The coloring of the stem of the latter changed smoothly from green to yellow and then to pink.

The seeds germinated in normal conditions and were not exposed to mutagens. The variegation of the seedlings is the result of recessive genes of the kernels of the embryo of the seed. These genes were passed to the posterity from the parent plants.

Certainly, almost all the seedlings got as a result of this crossing carry recessive genes that provoke mutations of plastids. But only a small part of such genes inside one zygote can give rise to the changes of coloring of epidermis in the process of postembryonic development. In this case the maternal plant was not rich in these genes, that is why the percentage of plants that are plastid mutants is rather low though the paternal plant is rich in them.

Glossary:
Genotype - all or part of the genetic constitution of an individual or group
Mutagens - agents that tend to increase the frequency or extent of mutation
Somatic mutation - genetic changes of vegetable cells.
Phenotype - the visible properties of an organism that are produced by the interaction of the genotype and the environment.

Fresh seeds of hybrid Neochilenia scoparia ї Neochilenia odieri were sown to the same tray with the seeds of other 14 species of cactuses in January 1999. The next day after the sowing I irradiated the whole tray with UV rays during 17 minutes. The distance from the seeds to the quartz lamp was not more than 20 cm.

photo 6.

The first seedlings appeared in 25 days after the irradiation. Their coloring corresponded to the "Chilean" norm, but they developed rather slowly. Losing patience in July I implanted 4 biggest seedlings to the short (1.5 cm high) Trichocereus sp.

The seedlings began to grow quicker on the grafts. In spring and summer 2000 they felt well on the south balcony. But in September I noticed strange changes of color on one of the grafted seedlings - it had reddish spots on the stem (photo 6). photo 6.

I am not sure in the causes of bi-color coloring of the plant. Phenotypic reaction of somatic mutation almost in two years after the mutagen influence seems rather strange. Though everything is possible.

Three shoots of the same Thamaecereus silvestrii were grafted to the stocks of three species (photo 7): Cleistocactus tupizensis - on the left, Trichocereus sp in the center and Cereus peruvianus on the right.

photo 7.

In a year the habitus of grafted "aurei" began to change so that three plants with identical genotype became different in phenotype though they developed in the same conditions. Each stock "set" its own "seal" on the graft.

Cleistocactus tupizensis "allowed" its graft to have long and thick thorns, and its epidermis had got a brownish shade. The graft of Trichocereus sp developed thick thorns too but rather short and white. Its epidermis remained yellow. The graft of Cereus peruvianus developed long rare white thorns, and its top was pink during the whole summer. The rest of epidermis was yellow.

Translation Irina Koudina, Moscow, Russia, e-mail: irink@os2.ru