temperature Influence. Morfogenetichesky effects

you are: temperature Influence

Very small speed of chemical reactions in a plant at low temperatures provides coordination of changes of growth with climatic changes. Besides, the temperature influences many processes sensitive by the photoperiod, changing critical length of the dark period though the mechanism of this phenomenon is not found out. As presence of Fdk could break an induction of flowering at a plant of short day at night, it would be possible to expect that the high night temperatures accelerating destruction of phytochrome and transformation by Fdk in Fk, will favour to an induction of flowering at such plants. Actually the opposite effect is usually observed. some plants it is possible to force to blossom by means of long dark nights or low night temperatures. Probably that each of these influences is capable to activate any process conducting to synthesis florigena.

Germination of seeds, interruption of rest of kidneys and preparation for a bookmark concern the most dramatic effects of low temperature flower bugorkov. The nizkotemperaturnoe influence promoting germination of seeds, name stratification, and facilitating initsiatsiju flowerings - jarovizatsiej. The first interferes with premature germination, and the second provides biannual type of development. As the optimum temperatures necessary for germination and jarovizatsii, for different plants are various, the temperature is the important factor influencing geographical distribution of plants and regulating time of flowering and plodoobrazovanija.

The Considerable part of data about jarovizatsii has been received in the researches spent on annual and biannual lines of a rye (Secale cereale). The annual line finishes the reproductive cycle for one vegetative period, and biannual rewintering is necessary for flowering in the field. dvuletnik in the first year forms only vegetative bodies; flower bugorki cannot be put until the plant will not undergo to long influence of low temperatures. Only after such influence it is capable to react to appropriate photoperiodic stimulus.

This requirement for low temperatures can be satisfied in any phase ontogeneza after germination of seeds. For example, if seed dvuletnika to allow to absorb a quantity of water to start germination, and then about six weeks to hold at low temperatures (approximately 2-5°С), the plant will behave as if it has worried cold winter after a year of growth, and will blossom at spring crops if there will be a corresponding photoperiod (fig. 12.23). As distinctions between annual and biannual races at the majority of plants, apparently, depend on one gene, the low temperature for the biannual form, possibly, takes the place of any genetically controllable biochemical event occurring at the annual form without influence of a cold.

Holodovoj stimulus is perceived by a runaway top, a fabric in which there is also a formation of flower kidneys. Therefore the effect of such stimulus unlike florigena, induced by the photoperiod, does not have necessity to move on a plant. The majority of the plants demanding jarovizatsii, are dlinnodnevnymi, and the photoperiodic induction after germination is necessary after a while to them. It allows to assume that the cold causes any local change of cages which gives the chance to them to react on florigen. The changes caused in low temperature, at the majority of plants after an induction remain vaguely long time. For example, jarovizirovannoe the condition is reproduced at thousand cellular divisions in apikalnyh meristemah; thus, jarovizatsii it is enough any kidney for transfer of its effect to all cages arising from this kidney.

At some dvuletnikov influence gibberellinom on the plant which has been not subjected jarovizatsii, probably, replaces low temperature, causing at the favorable photoperiod a fast bookmark flower bugorkov.

But as gibberelliny not always can replace holodovuju processing, it seems improbable that the effect jarovizatsii is entirely caused by synthesis increase gibberellinov. According to other assumption, jarovizatsija ' derepressiruet ' special genes in the cages processed by a cold - raises the blockade interfering specific processes of a transcription and translation. It is an attractive hypothesis as both at stratification, and at jarovizatsii synthesis of many enzymes amplifies.