Vernalisation

Are plants only dependent on light to flower and germinate? Is there any other factor that influences flowering? Yes! In addition to light, another factor that influences flowering in plants is temperature. This dependency on temperature is Vernalisation. Let’s learn this concept and how it affects flowering in plants in more detail.

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Vernalisation

Vernalisation is defined as the qualitative or quantitative dependence of plants on exposure to a low temperature to flower. Temperature affects flowering, metabolic activities, and germination of seeds in plants.

Plants that grow in mild weather germinate at low temperatures whereas those that grow in hot regions germinate at high temperatures. Some plants need exposure to a low temperature to germinate. Furthermore, a plant can be induced to flower in a growing season by exposing it to low temperature. Therefore, it shortens the vegetative phase and hastens flowering in plants.

Examples of Vernalisation

Food plants such as wheat and barley have a ‘spring variety’ and a ‘winter variety’. The ‘spring variety’ is usually planted in the spring season. As a result, it flowers and produces grains by the end of the growing season. The ‘winter variety’, however, is planted in autumn. It germinates over winter, grows in the spring and is harvested in summer. In contrast to the spring variety, the winter variety will not flower or produce grains within the flowering season if planted in spring.

Biennial plants are plants that take two years to flower. They grow leaves, stem, and roots in the first year and then enter a period of dormancy in the cold months. They need this period of cold or vernalisation to flower in the subsequent months. Eventually, biennial plants flower, produce fruit and die in the next spring/summer. Examples are carrots, sugarbeet, and cabbages.

Factors Needed For Vernalisation

• Low Temperature – 50-day treatment between 2°C and 12°C.
• Water – Plants need proper hydration to receive the stimulus from cold temperatures.
• Actively dividing cells – For vernalisation to work the cells need to be actively dividing. It does not work on dry seeds and therefore, the seeds need to be moist before exposure to low temperature.
• Nutrients
• Aerobic respiration

Site Of Vernalisation

The site that perceives the cold stimulus can be different in different plants. It could be the apical meristem in the shoots, the germinating seed or the vegetative parts such as leaves.

Advantages

• Prevents plants from maturing too early in the growing season. Therefore, they get enough time to mature.
• Induces early flowering and reduces the vegetative phase of plants.
• It increases yield in plants.
• Provides resistance to cold and diseases.
• It enables biennial plants to behave like annual plants.
• Vernalisation allows plants to grow in regions they normally do not grow.
• Also, it helps to remove the wrinkles on kernels of Triticale (wheat and rye hybrid).

Solved Example For You

Question: Vernalisation reduces which phase in plants?

1. Growth phase
2. Vegetative phase
3. Differentiation phase
4. Flowering phase

Solution: The answer is ‘b’. Vernalisation reduces the vegetative phase (phase where leaves are produced) and induces early flowering in plants.