2. VERNALIZATION:
• Vernalization is the process whereby flowering is
promoted by a cold treatment given to a fully
hydrated seed or to a growing plant.
• seeds do not respond to the cold treatment.
• Due to the vernalization the vegetative period of the
plant is cut short resulting in an early flowering.
• Without the cold treatment plants that require
vernalization show delayed flowering or remain
vegetative.
• In many plants grow as rosettes with no elongation of
the stem.
3. • Vernalization is defined as the method of inducing early
flowering in plants by pretreatment of their seeds at very low
temperature. the ability to flower by chilling treatment.
• Plants do not flower unless In many plants, temperature has a
profound effect on flowering. Some they are exposed to
prolonged periods of cold temperatures.
• Biennials remain vegetative during the first season, and after
being exposed to the cold temperatures of winter, they flower
in spring.
VERNALIZATION:
4. • However, if they are subjected to cold
treatment followed by correct photoperiod,
they will flower.
• For example, the biennial henbane
(Hyoscyamus niger) a long day plant, can be
made to flower within one growing season,
provided it is exposed to low temperatures
followed by the correct photoperiod.
5. History:
• Klippart; 1857 first noticed the low
temperature requirement for flowering while
working with winter wheat and spring.
• Lysenko ;1938 used the term vernalization for
a low temperature promotion of flowering in
plants.
• Chourad;1960 –define vernalization as
acquisition or acceleration of the ability of
flower by a chilling treatment.
6. • Vernalization prepares the plant for flowering.
• The cold stimulus usually perceived by the
apical meristem. But in some species all
dividing cells of roots and leaves may be the
potential sites of vernalization . e.g Leennorio
biennis.
• Vernalization induces the plant to produce a
harmone called vernaline. It was discovered
by Melcher 1936.
• The vernalization stimulus can be transmitted
from one plant to another through grafting.
7. • The age of the plant is an important factor in
determing the responsiveness of the plant to the
cold stimulus and it differ in different species.
• Temperature suitable for vernalization is ranges
between 1to6c.
• Its an aerobic process and require metabolic
energy.
• Absence of oxygen cold treatment becomes
completely inefficient.
• Sufficient oxygen is also essential.
• Vernalization of dry seed is not possible.
8. • For vernalization, the seeds are allowed to
germinate for some time and then are given
cold treatment by keeping them at 0-5°C.
• The period of cold treatment varies from few
days to many weeks from species to species.
After the cold treatment, seedlings are
allowed to dry for some time and then sown.
• They should not be sown immediately after
the cold treatment.
9. • Effects of Vernalization on Plants | Botany
• In many plants, temperature has a profound effect
on flowering.
• Some plants do not flower unless they are exposed
to prolonged periods of cold temperatures.
• Biennials remain vegetative during the first season,
and after being exposed to the cold temperatures
of winter, they flower in spring.
• Majority of plants will not flower if they are not
subjected to exposure and will grow vegetatively
for an indefinite period.
10.
11. Even the biennial type can be made to flower if its ten
days old seedlings are subjected to cold treatments. For
vernalization the seeds are allowed to germinate for
some time and then are given cold treatment by keeping
them at 0-5°C. The period of cold treatment varies from
few days to many weeks from species to species.
12. Temperature as a vernalization effect as
well as during photoperiodic treatments
has been found to be an important factor
regulating flowering. There is evidence to
suggest that vernalization effect could
involve such substances as gibberellins.
The interaction between photoperiod and
temperature is considered important in
the flowering of many crop plants.
•
13. Mechanism of vernalization:
Two theories:
• Phasic development theory
• Hormonal theories
• Phasic development:
• Proposed by Lysenko in 1934.
• This theory explains that there is a series of phase in the
development of a plant.
• Each stimulated by environmental factors such temperature and
light.
• Hormonal theories:
• Melcher1939
• Chilling treatment induces the formation of a new floral
harmone called vernaline.
