The first phase of plant development , the vernalization phase begins from the moment when a seed only starts to move in the growth and is held under

Vernalization in plants

The first phase of plant development, the vernalization phase begins from the moment when a seed only starts to move in the growth and is held under the influence of certain conditions of temperature and aeration, as well as the water content of the body's cells. Phase of vernalization cannot take place in the dry seed. It should be noted that the set of conditions, under which correspondent phase of development goes, is the one to which current species of plant has adapted over many generations in this climatic region. It is therefore clear that the conditions for the passage of the vernalization phase in plants of southern origin, such as cotton, are sharply different from the conditions of this phase passage in plants of more northern type, such as winter wheat. In cotton vernalization phase takes place at a temperature of 25 °C, and in winter wheat — from 0 to 5 °C (if the rest conditions present: aeration and water content of cells).

It should be emphasized that changes in growth points of the plant that were described by numerous authors are not the very essence, but merely a consequence of the vernalization process. This category of changes include changes in the isoelectric point of protoplasm proteins, increase of enzyme activity, and the formation of Prussian blue due to the processing of points of growth with Potassium ferrocyanide and ferric chloride — reaction typical for vernalized plants, according to Bassarskaya.

Phasic changes, that are associated with the passage of the vernalization phase, are carried out in the growth cones and pass from one cell to another by dividing the mother cell. Proofs of this situation are the experiments with soybeans and cotton cuttings. Cuttings of these plants taken from different parts of the stem, gave different results in flowering. While plants from cuttings taken from the top of the plant, near the growth point, gave the rapid flowering, cuttings taken from the base, in spite of his old age, were phasically younger, i. e. flowered later or never flowered. Phasical quality difference of tissues is shown on another experiment (diagram 209). Soybean plant that was grown from cuttings taken from a flowering plant, i. e. phasically older, has blossomed, and the one that was grown from cuttings taken from non-blossoming plants, i. e. phasically younger, has not bloomed. The experience was carried out under continuous light, at which the photo phase in soybeans does not pass. Taken from http://worldofschool.org

Diagram 209. Soybeans. Both plants were grown under continuous illumination. Left the plant — from cuttings taken from the non-bearing plants, the right plant — cuttings from fruiting plants. The left plant did not bloom, right — blossomed and yield a fruit

Direct experiments on cooling of the growth points in beet that were held by the Polish scientist Hrobochek by the supply of cold water in the rubber tube, showed that vernalization occurs only in the case of cooling of growth points. If you cool the plant itself, the vernalization phase won’t pass.

It is interesting to note that a number of biennial plants (beets, cabbage) pass vernalization phase only in a state of green sprouts, and do not pass it to the seed. Obviously, vernalization phase in these plants begins to take place when the plants of the heterotrophic nutrition via stockpiles, deferred by the mother plant in the seed, go to autotrophic nutrition via green leaves.

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