Vernalisation

Introduction

The artificial method of vernalisation was discovered by a Russian worker, Lysenko, in 1928. The term “vernalisation” originated from the Latin word ”Vernalis” which means “of the spring.”

Vernalisation is an artificial exposure of plants (or seeds) at low temperatures to stimulate flowering or to enhance seed production. It refers to the acceleration of flowering that occurs following prolonged exposure of seeds or young seedlings to low temperatures. 

Plants that are vernalised do not flower immediately upon exposure to higher temperatures but later, such annual and biennial plants can be grown at a low temperature or in a moistened seed environment. 

Gibberellin is a hormone that replaces vernalisation.

Conditions

The process of vernalisation is affected by the following factors:

• Age of the plants
• Site of vernalisation
• Provision of suitable low temperature
• Oxygen
• Duration of exposure to water

Examples: Spring and winter are two varieties found in food plants like wheat, barley and rye.

• Spring – It produces grains before the same growing season
• Winter – They are planted in autumn. These varieties are planted between September and October for germination during winter

Spring varieties of crops are harvested by mid-summer.

• Biennials – The life cycle of these plants is two years, where flowering occurs at the end of the second year. Some examples are carrot, beet, cabbage and turnip

Functions

• The stimulus of cold treatment which is known as vernalisation is readily perceived by the shoot tips, embryo tips and other meristematic regions of the plant
• Many plants grow in a temperate climate in low winter temperatures to initiate the flowering process to ensure reproductive development and seed production in spring and winter rather than autumn
• The plants must reach vegetative maturity before reproduction
• Fruit trees, including apples and peaches require minimum cooling in winter to produce a good crop
• Too warm winters can damage the trees’ health or even kill them over time

Process

• The process of vernalisation is significantly employed in food plants, such as wheat, barley and rye etc.

• Biennial plants such as cabbage, sugar beet and carrot etc.
• Perennial plants like chrysanthemum etc.

• The gardeners’ version of vernalisation can be placed in an airtight bag or container in some lightly moistened clay for two weeks
• Flowering is facilitated by a cold treatment provided to a completely hydrated seed or to a growing plant
• The vegetative phase of the plant is restricted, which leads to early flowering
• Without the cold treatment, those plants that need vernalisation exhibit a delayed flowering or stay in a vegetative state

Importance

• Vernalisation ensures that plants do not flower in the fall when the environmental conditions are unfavourable for reproduction
• Photoperiodic/photoperiods determine the season in which a particular plant shall come to flower
• The strength of the vernalisation requirement can vary within the plant species
• It lifts the yield, providing obstruction to parasitic illnesses
• It builds the chilly obstruction of plants
• It aids in the progress of harvest

Method

The system of vernalisation is clarified by two primary speculations: synthetic nature hypothesis and stage advancement hypothesis.

1. Synthetic nature of vernalisation: 
2. Melchess accepted that a theoretical chemical named vernalin is created during the low-temperature treatment.

• The upgrade is obtained by the separating cells of the shoot for example apical meristem or the undeveloped organism tip
• The vernalin chemical prompts a physiological change in the plant that incites blossoming
• Be that as it may, a few physiologists accept that the plant development of the chemical gibberellin increments during vernalisation

2. Physic/Aphasic development theory: 

The Russian physiologist Lysenko set forward the phasic improvement hypothesis. He recommended that each plant goes through two periods of improvement: thermo phase and photo phase. Ecological variables control these two stages.

• Thermo phase: The thermos/therms phase is in the beginning stage of life and requires an unmistakable temperature for improvement. It is mostly applied for the development of seeds and seedlings
• Photo phase: The photo phases are in the late period of life and require an unmistakable light and dim period for blossoming

Advantages

The advantages of vernalisation are:

• It induces early flowering and reduces the vegetative phase of plants
• It increases yield in plants
• Because of it, winter variety crops can be easily converted to spring variety crops
• It can remove seed tips in wheat and rye fusion
• Its resistance towards different types of mitosis/meiosis is increased in a given environment
• Fewer cases of tropical plants grow in temperate areas
• Its resistance capacity for cold or frost is increased
• It provides resistance to the cold and diseases
• It enables biennial plants to behave like annual plants

Note

• Vernalisation prevents precocious reproductive plants by exposing the plants to low temperatures to reach maturity
• Rice doesn’t show vernalisation, whereas spring and winter require cold treatment

Types of Vernalisation

• Obligate vernalisation – Plants at lower temperature for specified period. For example, cabbage
• Facultative vernalisation – Biennial plants

Similarities

• Both are physiological and have agrarian applications
• Plant chemicals interfere with the two cycles

Differences between Photoperiodism and Vernalisation

• The key difference between photoperiodism and vernalisation is that photoperiodism is regulation of plant development in the length of day/night, while vernalisation is low-temperature treatment that promotes flower growth
• Vernalisation is an artificial treatment, whereas photoperiodism is a natural process
• Vernalisation produces early flowering, but photoperiodic/photoperiods regulate plant development and early flowering
• Vernalisatrion is reversed by exposure to high temperature and photoperiodism by exposure to unfavourable conditions

Photoperiodism vs. Vernalisation

Both photoperiodism and vernalisation are significant for the inception of blooming.  

Photoperiodic/photoperiods are the reaction of plants to the general lengths of light and dim periods. Above all, the inception of blossoming is an aftereffect of photoperiodism. Then again, vernalisation is the chilly treatment that advances early blooming in angiosperms. Consequently, this is the critical distinction between photoperiodism and vernalisation.

Importance of Photoperiodism

• Photoperiodic/photoperiods determine the season in which a particular plant shall come to flower
• The knowledge of photoperiodic/photoperiods’ effect is useful in keeping some plants in vegetative growth, to obtain higher yield of tubers, rhizomes etc or to keep the plant in reproductive stage

Example of Photoperiodic/Photoperiods

• When a plant doesn’t bloom during the increased darkness of wintertime
• Many plants exhibit photoperiodic/photoperiods by flowering only after being exposed to a set amount of daylight, by requiring either a long or short day to flower
• The cells of the plants that are farthest from the light have a substance called auxin that responds when phototropism happens. This makes the plant have prolonged cells on the farthest side from the light

Conclusion

Vernalisaton and photoperiodism differ in the germination of the plant regarding the conditioned environment. Vernalisation is an artificial exposure of plants (or seeds) at low temperatures to stimulate flowering or to enhance seed production. It refers to the acceleration of flowering that occurs following prolonged exposure of seeds or young seedlings to low temperatures.