INTRODUCTION. Variability is one of the main characteristics of a living organism. This is what makes them different from unvaried inanimate objects. This characteristic is as important as metabolism, propagation, heredity and others.

The term "variability" is rather vague and is understood in different ways. As a prominent Dutch geneticist and botanist Gugo de Friz said in his work "The Theory of Mutation" (1901): "There is nothing more variable than the meaning of the word "variability". Some authors use it in such a wide sense that you can not understand what they mean".

The Great Darwin considered variability as one of the two most important factors of evolution but did not classify its phenomena as did not realize fully their diversity. He used a general term "variation".

In 1913 a Dutch geneticist B.Iogansen divided the phenomena of variability into two groups: hereditary and non-hereditary, which was an important contribution.

Now it is individual variability or difference between individuals within a species that is understood under variability.

On the other hand, you can find group variability or intraspecific polymorphism. We tell about it when there are groups of individuals (breeds, sorts, subspecies, clones and others) that differ significantly within a species. According to a Soviet geneticist Yuriy A.Filipchenko (1925), we use this meaning when we say that hens are more variable than peacocks or turkeys, dogs are more variable than cats1 and so on.

Yuriy A.Filipchenko was right to assert that the term "variability" includes two elements – static (variability as a state) and dynamic (variability as a process). He also said that "the studies of variability go from static that demands variational and statistical method to groups and then to variability as a process".

In 1972, S.A.Mamaev – Director of Botanic Garden of the Ural department of the Russian Academy of Sciences – singled out 6 main forms of variability basing on literature and his own researches: individual, sexual, temporal (chronographic), ecological, geographical and hybridogene.

Later he also singled out endogene variability which he understood as variability of even-aged structures within an organism.

In our opinion and in other researchers' opinion, one should start studying variability with endogene variability because it allows to find "in pure form" the differences between genetically similar and even-aged structures (tissues, organs and others) of the same plant which are caused by the exterior influence and are connected neither with time nor with genotype differences.

I should mention that actually endogene variability stands close to ecological one as it is caused mostly by environmental factors that influence genetically similar material. In other words, studying endogene variability allows to certain degree to model ecological variability.

So, when we started examining individual variability of the contents of pigments of CFC we began with endogene variability, or the differences within an organism caused by different locations of the tissues within a plant, and temporal (chronographic) variability connected with age differences of the tissues.

MATERIAL AND METHOD. In June 2001 the contents of chlorophylls a and b and of carotinoids at a big 5-year old and six 2-years old CFC "Multicolor" (a three-color yellow-red-green variegated form ("Hibotan") were studied in Botanic Garden of the Ural University. (Photo1)

Before the research the plants were kept in a green-house at temperature of +20-25(С with good natural light during a month. The orientation of the cacti to the light was the same during 2 years.

We took mainly the parts of the exterior zone of the rind together with hypodermis and epidermis 1.5 mm thick of different age (1 to 5 years old) from the ribs and between the ribs, from the Southern and the Northern sides, and also the following:

• 1-year old parts of the interior rind 3-4 mm deep from the surface;
• 1-year old parts of the core inside the ring of conducting clusters (the so-called "cambial ring");
• scions of about 1 cm in diameter;
• buds and flowers including separate petals.

We weighted the samples on the torsion scales and fixed them in ammonia vapor. Then the samples were reduced to fragments, and the pigments were extracted by acetone. The concentration of pigments in mg/g of raw weight was determined with spectrophotometer "Lomo" SF-46. The test was repeated three times for each variant.

RESULTS AND DISCUSSION

1. THE INFLUENCE OF THE TYPE AND ORIENTATION OF TISSUES As we have already mentioned "there are more differences in the different parts of the same plant that are genetically similar. There is a graphic example: CFC "Multicolor" develops scions of different colors – from almost black to almost purely orange-red. The former have almost twice as many pigments, especially chlorophylls, as the latter. The conclusion was proved by further researches (table 1)

Table 1

There are more pigments in buds than in all the somatic tissues except black scions. There are less pigments in petals than in the basis of ovary.

The contents of photosynthetic pigments are much lower in the interior zones of rind, 2-3 mm beyond the surface and still much lower in the core (more than 10 mm below the surface) where the light is unlikely to penetrate.

Probably the process of photosynthesis is more active in buds than in somatic tissues except black scions. High values of АВ/С and А/В indicators also point to this.

Table 2

The data from table 2 is very indicative. It is known that the ribs of a cactus absorb more sunlight than zones between ribs as the ribs shade them. This is why the index АВ/С differs 2-3 times. Index А/В showed opposite results with different stocks (echinopsis, eriocereus) and needs additional study.

Significant differences at the same tissues of the same cactus prove that there is a connection between these indices and:

• environmental parameters;
• different intensity of metabolism in somatic and generative tissues.

2. THE INFLUENCE OF ORIENTATION NORHT/SOUTH. As one of cactophiles' rules is to keep the orientation of light to the plants we observed it with test plants. It is obvious that "northern" and "southern" parts of a cactus are in unequal conditions of light and temperature. Does it influence the quantity of pigments of CFC?

Table 3 shows very clearly this influence. At the southern side there are less chlorophylls (AB) and pigments in general (АВС), the ratio " chlorophylls to carotinoids" is also less (АВ/С), and there are more chlorophyll a as compared to chlorophyll b (А/В). The contents of carotinoids at the southern and northern sides are practically equal.

Table 3

3. THE INFLUENCE OF THE AGE OF TISSUES. We all know that CFC are short-lived. Aging plants look "paler" than young ones. At what age do the tissues contain the maximum of pigments and when does it start decreasing?

Table 4 shows the maximum contents of chlorophylls, pigments in general, ratio "chlorophyll to carotinoids" and " chlorophyll a to chlorophyll b" at the second year of the life of tissues. The maximum contents of carotinoids were found at the growth of the current year that is in the youngest tissues of the rind close to the top of the cactus.

Table 4

Starting from the third year (the second – for carotinoids) all the mentioned indices go down smoothly. It is best seen at the age of 5.

As we have already mentioned the contents of carotinoids is 5-6 times higher in young tissues (the growth of the current year) than in 4-5 years old tissues. It means that in aging tissues the contents of photosynthetic pigments decrease quickly, almost arcwise. (Skoulkin, Artemieva, 2000).

As we see now 5-6 times difference may not occur, but one can certainly find 2-3 times difference between young and old tissues.

I would like to specify the idea of "almost arcwise" decrease of pigments with age. Probably it is correct with reference to carotinoids. As for other indices they increase till the second year of the life of tissues and than begin to decrease smoothly that is "almost" (thought not exactly) arcwise.

CONCLUSIONS

1. We found significant differences of the contents of pigments and their indices in different parts of the same plant by the example of CFC "Multicolor". The contents of pigments is higher in scions than in the young tissues of maternal plant, and they are 2-3 (up to 5-6) times higher in the latter than in below lying tissues of 4-5 years old. It proves the idea of quick aging of CFC when the contents of photosynthetic pigments decrease quickly.

2. The amplitude of endogene and ontogene variability or the maximum difference between the parts of the same plant is more than 10х for the sum of pigments, up to 9х for ratio А/В, up to 7х for АВ and С, and only 3х for АВ/С (chlorophylls to carotinoids).

3. Indices АВ, С, АВС, АВ/С of black scions surpass those of light-orange (orange) scions. They are higher at the Northern side than at the Southern and between ribs than on them, they are maximum in 2-years old tissues as compared to younger or older ones though the contents of C is maximum in the youngest tissues.

4. АВ/С (1,15-3,89; average 2,17) is very low as compared both to shade-requiring plants – sciophyte (5,3-5,7) and light-requiring – heliophyte (3,6-4,6). The cause is mostly evident. It is very low contents of chlorophylls.

5. Though А/В is higher at black scions as compared to light ones and is maximum in 2-years old tissues it is significantly higher at the Southern side than at the Northern. Its value in CFC "Multicolor" is very low as compared to the data described in the literature (0,5-2,2; average 1,4 vs 2,3-3,0 for sciophytes and 4,4-5,6 for heliophytes). [The data to be compared is from: Goryshina, 1979]

6. To compare different species and forms of cacti it is necessary to take parts of corresponding tissues of the same age and to observe their orientation to cardinal points, otherwise significant endogene and ontogene variability will not allow to recognize clearly the differences between species and forms that is group variability.

LITERATURE

1. Mamaev S.А. Variability and Methods of Study. Sverdlovsk, 1972
2. Skoulkin.I.М., Artemieva Е.P. The contents of photosynthetic pigments at CFC and some other succulent plants. "Not Only Cacti", 2000,№ 4.
3. Skoulkin.I.М., Koulmina I.А. Comparative analysis of influence of different types of stocks over the growth and development of CFC. "Not Only Cacti", 2000,№ 1.
4. Filipchenko Yu.A. Variability and Methods of Study. Moscow-Petrograd, 1923

Translation Irina Koudina (Okounkova , Mosсow, Russia, e-mail: irinkos2@yandex.ru)