Annual plants is influenced by temperature for flowering is secondary to that of light. Biennials and perennials remain vegetative during first growing season After prolonged exposure to cold temperature of winter flowering occurs during following season. Without cold exposure majority plants remain vegetative

2.  Annual plants is influenced by temperature
for flowering is secondary to that of light.
 Biennials and perennials remain vegetative
during first growing season
 After prolonged exposure to cold
temperature of winter flowering occurs
during following season.
 Without cold exposure majority plants remain
vegetative

3.  Vernalization (from Latin vernus, "of the
spring") is the induction of a plant's
flowering process by exposure to the
prolonged cold of winter, or by an
artificial equivalent.
 After vernalization,
plants have acquired the ability to
flower, but they may require additional
seasonal cues or weeks of growth
before they will actually flower.

4.  Many plants grown in temperate climates require
vernalization and must experience a period of
low winter temperature to initiate or accelerate
the flowering process.
 This ensures that reproductive development and
seed production occurs in spring and winters,
rather than in autumn.
 The needed cold is often expressed in chill
hours.
 Typical vernalization temperatures are between 5
and 10 degrees Celsius (40 and 50 degrees
Fahrenheit).

5.  In the history of agriculture, farmers observed a
traditional distinction between "winter cereals",
whose seeds require chilling (to trigger their
subsequent emergence and growth), and "spring
cereals", whose seeds can be sown in spring, and
germinate, and then flower soon thereafter.
 Scientists in the early l9th century had discussed
how some plants needed cold temperatures to
flower.
 In 1857 an American agriculturist John Hancock
Klippart, Secretary of the Ohio Board of
Agriculture, reported the importance and effect
of winter temperature on the germination of
wheat.

6.  The formal definition was given in 1960 by a
French botanist P. Chouard, as "the
acquisition or acceleration of the ability to
flower by a chilling treatment".

7.  The site of cold stimulus, in most of the plants, is
meristematic cells in the bud.
 In those plants where a low temperature treatment
of seed is effective, experiments with excisedembryo
have visible that the apex of embyo is the site of
perception.
 For instance, the various parts of a plant excluding
the other parts were given cold treatments and
observations were made for subsequent flowering.
 It was found that flowering occurred when
meristematic cells of the plant were treated with cold.
 It has been well established now that meristematic
cells are active site of cold stimulus.

8.  It is possible to devernalize a plant by
exposure to sometimes low and high
temperatures subsequent to vernalization.
 For example, commercial onion growers store
sets at low temperatures, but devernalize
them before planting, because they want the
plant's energy to go into enlarging its bulb
(underground stem), not making flowers.

9.  The German botanist G. Melchers in 1939
demonstrated that the yield of vernalization
could be transmitted from a vernalized to an
unvernalized Hyoscyamus plant through a
graft union .
 He termed this substance as vernalin
However, the vernalin is a hypothetical
substance and has not been isolated.

10.  The explanation of mechanism is based on some
important findings. For instance, it has been found that
high temperature, following the low temperature
treatment, nullified the flowering effect.
 This purpose that the yield of cold treatment can be
metabolized away if the low temperature is immediately
followed by high temperature, before the yield
establishes its influence.
 If the cold treatment is not immediately followed by the
high temperature(a destroying system) System), the
unstable yield of vernalization starts accumulating.
 This unstable substance is then changed to the stable
vernalin.

11.  Later A. Lang et al, (1957) demonstrated that
application of gibberellins may replace the cold
treatment for vernalization in several plants.
 Further, it was shown that endogenous level of
gibberellins was increased in vernalized plants.
 Because the vernalin has not been isolated and
identified, it is proposed that the yield of
vernalization that induces flowerin could be a
particular gibberellin or a mixture of
gibberellins.
 Therefor , the correct mechanism is still not
known and required through investigation.