Vernalization

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Vernalization

The induction in plants of the competence or ripeness to flower by the influence of cold, that is, temperatures below the optimal temperature for growth. Vernalization thus concerns the first of the three phases of flower formation in plants. In the second stage, for which a certain photoperiod frequently is required, flowers are initiated. In the third stage flowers are unfolded. See Flower, Photoperiodism, Plant growth

Vernalization

 

the reaction of a plant that is in the vegetative state to the effect of low, above-freezing temperatures (2°–10°C) for a certain period of time. Vernalization finds expression in the plant’s unique preparation to form the rudiments of flowers at the growing point. The German botanist J. G. Gassner was the first to study the phenomenon of vernalization (1918).

The phenomenon is characteristic of winter plants and some biennials and perennials. In some plants the formation of the flower rudiments may be an immediate result of vernalization. In many, for example, winter grasses, biennial henbane, and winter rape, flowering after vernalization will only occur during long days. Some plants show a capacity for vernalization at an early age. In winter grasses the reaction is observed during seed germination, and in biennial henbane it occurs after one month.

Vernalization is the result of the adaptation of plants to seasonal changes in climate. The physiological mechanisms of vernalization are probably associated with the formation of the plant hormones involved in inflorescence development.

The term “vernalization” is also used to designate an agricultural procedure by which the seeds of winter crops are exposed to a low, above-freezing temperature before planting so that the plants will blossom when planted in the spring. The technique is used in the selective breeding of plants.

V. Z. PODOLNYI

vernalization

[‚vərn·əl·ə′zā·shən]
(botany)
The induction in plants of the competence or ripeness to flower by the influence of cold, that is, at temperatures below the optimal temperature for growth.
References in periodicals archive ?
(1960) Vernalisation and its Relations to Dormancy.
Relationship between vernalisation requirement and winter hardiness in doubled haploids of barley.
RFLP mapping of the vernalisation (Vrn-1) and frost resistance (Fr-1) genes on chromosome 5A of wheat.
With their requirement for vernalisation -- exposure to a period of winter cold -- Arabidopsis ecotypes from northern Europe have something in common with fruit trees such as cherries and apples, and the winter wheats of colder regions of Europe and North America.
Plant Industry chief Dr Jim Peacock wondered if methylation might be the mysterious mechanism responsible for vernalisation. Perhaps exposure to cold stripped methyl molecules off the DNA to reactivate a suppressed gene in the flowering pathway for winter wheat?
`Nobody believed us when we suggested that methylation controlled vernalisation by suppressing the genes involved in flowering,' Dennis says.
Now they have shown that cold-shocking cold-tolerant ecotypes of Arabidopsis seedlings to simulate vernalisation suppresses the FLF gene's activity, initiating early flowering.
Dr Jim McVittie, the HGCA Recommended Lists manager, warns however that most winter wheat varieties do require a period of cold (vernalisation) before they will flower so complete crop failure can result if they are sown too late.
``The vernalisation requirement is different among the varieties on the HGCA Recommended Lists so some can be sown later than others,'' said Dr McVittie.
Winter oats do not have a vernalisation requirement so can be sown at any time in the spring, but yields of winter varieties tend to be lower than those of spring varieties when sown after the first week of March.
For example, new machinery, herbicides or tillage practices may enable earlier sowing and the best adapted cultivars to these conditions may require different sensitivities to photoperiod or vernalisation than for currently grown cultivars.