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the biological body cell has "sub-totipotency property"
Chen Shao Xiong
The Comprehensive Secondary School of Jieyang,Guangdong Province
Abstract:Three years of repeated experiments,with the technology of tissue culture and on the materials of sansevieria,dracaeba and banana sprout tips,show that the plant body cell not only has "totipotency property" but also has "sub-totipotency property".
Keyword:totipotency property; sub-totipotncy property; plant body cell; tissue culture; body cell breeding; bio-diversity; clone animal; body cell choosing;
The biotechnology,rising vigorously in the world at present,has been bringing about an enormous change in agriculture and forestry.It has already been widely used in such a lot of fields as variety seed selection,improved seeds fast reproduction,etc.Tissue culture is an extremely important field of biotechnology.Of research in cytology,heredity,physilolgy,biochemistry,etc.,tissue culture is one of the effective means,too.Its development has helped promote a lat of foundational coueses of biology greatly.
I.Reserch and Development of the Theory on Plant Cell's All-round Property
The means of tissue culture,wihch can contribute to fast reproduction of a loat of plants,has already been applied to production extensively.Ti has opened up a new field for fast reproduction of the nursery stock.And the theory on cell's totipotnecy property and its confirmation provide the theory and practice for fast reproduction with a foundation.
As far back as 1902,G.Haberlandt,German botanist,proposed that high plant tissues and organs can be split apart constantly,until the individual cell,and each cell has ability of splitting further,separating and development.He attempted to culture a mesophyll cell and then grow it a complete plant outside the body.But,because of the limitation of experimental conditions at that time,the result is not successful.However,the scientific hypothesis that he put forward has been attracting and instructing a lot of scientific workers to continue exploring research all the time.
White,American scientist,by experimenting on tobacco stem section forming layer as a material,cultured a tobacco plant in 1937,and it could breed and develop in the test tube.At the same time,he cultured tomatoes and carrot root tips into asexual system successively.Thus,on the basis of gathering a lot of scientific experiments,he put forward the theory that "the plant cell is totipotent"in 1943.In other words,every cell of the plant like embroy cell,can be cultured into a complete plant outside the body.
Steward of USA tried to culture the individual carrot body cell by liquid rotation in 1958,adjusted the proportion of culture media to many kinds of hormones repeatedly,and induced a complete plant at last,which could blossom and bear fruit.This great break-through not only verified G.haberlandt's imagination that "the cell is totipotent",but also opened a new field for research of organ formation and embryo growth in the tissue culture.
II.Proposition of Plant Cell's Totipotency Property
Through 20 years of biological teaching,cytology experiment,theoretical research and practice of plant tissue culure,the author finds that the plant body cell shows "sub-all-round" property in tis relization of"getting totipotent".Namely,some body cells,during the process of performing their"totipotent property" to become a complete plant,surmount or fail to totally express the hereditary properties of their species and functions in some hereditary properties and function characteristics,until new hereditary properties and functions are produced.That is to say,between cells of the same plant tissue and cells of different organs and different tissuues of the same plant,have existed different hereditary properties and different functions.
III.Evidence of Plant Cell's Sub-totipotency Property
1.Experiments on Sansevieria
In horticulture,the breeding methods of sansevieria include the plant-split breeding approach and the leaf-inserted bleeding approach.In the golden-rimmed sansevieria reproduction, if the plant-split reproduction approach is applied,the posterity generated can keep the beautiful color of yellow leaf edge;if the leaf-inserted reproduction approach is used,the posterity will not show the yellow leaf predestination like this beautiful color.The author made the comparison of these two kinds of reproduction methods during different seasons through three years from 1988 to 1991,and obtained the same result.
2.Experiments on Dracaena
The author,through four years between 1991 and 1995,eight times in different seasons,sectioned the stem of agate coral dracaena(golden-rimmed) and cultured it as outside plant body by the means of tissue culture.Nearly one thousand test tube plant shoots were produced each experimental time. The result was that over 90% of tube shoots could not keep yellow beautiful color of leaf predestination(golden-rimmed)each time,and all grew green leaves.
3.Experiment on Banana Sprout Tips
The peel of ordinary bananas changes its color from green to yellow,and the peel of red-peeled bananas turns from mauve to red.The author sectioned the sprout tips of red-peeled bananas to culture it into seedlings by the method of tissue culture six times in diffrent seasons between 1996 and 1997.5000 test tube shoots were cultured each time.95% of the plants grown from the test tube shoots bore the mauve fruits in the production of land for growing field crops,about 5% of the body-connected baby-plants produced the green fruits,and six times of test tube shoots resulted in almost the same proportion.Interestingly,we found in the production of land for growing fields crops that one maternal plant bore the mauve fruit,and the body-connected young plants bore the green fruit.We also found that another maternal plant bore mauve fruits,and a body-connected yound plant located in northeastern direction bore green fruits,but a body-connected young plant in southwestern direction still formed the mauve fruits. In this way,one maternal plant reproduced two different kinds of young plants asexually at the same time.
IV.Initial Analysis of the Theory on the Cell's Sub-totipotency
In terms of genetics, every cell is developed from the fertilized egg by mitosis. It is supposed to carry the same genetic information, and has the same shape structure and the same genetic functions. But the fact is not so. Every individual body grows different tissues and different organs by cell division and cell split. Therefore, cell split provides organism complication with the necessary material bases in the precess of the individual body growth.
Cell split is a process in which cells or organs form different structures and their functions or potential growing modes change. It results in the new structures and new proteins of cells and organs.
Cell split is a kind of response to chemical environment. Particularly, it refers to an embryo cell's changing appropriately in chemistry and on the shape, making it remarkably different from its initial state. Cell split happens when cells combine into the different proteins. Gene duplication leads to the protein characteristics. Cell split, as a result, helps cells to discern each other, thus join gluing together selectively to form a tissue. The response of the tissue cell in various degrees to the chemical environment determines the different hereditary properties and functions.
In suitable conditions, cells have reversible rotating property, which can split up, stop splitting up, and re-split up.
The cell splits up and forms the tissue, which has very important meaning to living beings. First, the tissue has offered the material base for forming more complicated organism structure. The cells of multicellular organism, because of their great number and big size, can form more complicated structures by splitting up in broader scope and at multi-layer levels---tissues, organs, and systems---which can make the structure of the biological organism more complicated and more advanced. Second, the tissue has offered the shape foundation for the individual body to exchange with the external enviroment. Multicellular organisms exchange materials with the external environment, and it will present the contradiction between the surface area and volume unavoidalbly. Plants solve this contradicion by means of the mass of leaf surface, developed root systems and vascular bundles composed of various kinds of tissues. Third, the tissue is an important form which improves physiological function and efficiency. The cell which has already been split into the tissue is not the totiotent cell like the embryo cell any longer. It may surmount or fail to totally express the originally inherent "totipotency", but it carries out a certain specific function more efficiently, and its other funcions weaken greatly. This is an important leap in the biological evolution course of multicellular organisms. However, while realizing the important evolving leap, multicellular organisms make the different organs and different tissues of the same plant show different hereditary properties and different funcions unavoidably.
V.Problem and Expecion
At present, biotechnology is widely used in production and people hope for a perfect explanation of bio-diversity. So it is undoubtedly important and meaningful to explore the cell's sub-totipotence. It can help people, according to their own purposes, screen and choose the modes of tissue culture and cell plasm body culture to produce the regenerated variation plant, and carry on alternative body cell breeding to shorten the breeding cycle. It can help people screen aimed cell, raise the secondary supersession produce output based on the plant cell culture technology. And it can help people to provide the theoretical foundation for explanation of bio-diversity.
The animal's cell has "sub-totipotency", too. The British "many jasmine" sheep was cloned by the mammary gland cell two years ago. Japan and New Zealand scientist not long ago succeeded in cloning with the ovary and oviduct cell respectively. Yang Xianzhong, scientist of Chinese origin of U.S.A., has succeded in cloing "Amy" with ox's ear cell recently. It is reported the British "many jasmine" sheep appears early ageing phenomenon already, which puts forward on to people one remain-solving problem that is worthy of study: we must choose the ideal cell to clone while cloning animals, thus we could achieve the goal of optimizing.
(Particular thanks are due to Gang Zgou, professor with Shantou University, Ceng Xiaolong, Associate Professor with Guangdong Institute of Education, for their guidance and modification of this paper.)
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