photoperiodisum, its types ,phytochrome and its role and vernalization, its site & requirement, mechanism and devernalization and its importance.

1. IMPORTANCE OF
PHOTOPERIODISM &
VERNALISATION.
SUBMITTED BY- LOVELY NAGRA

2. CONTENT Photoperiodism-
Introduction
Types
phytochrome
Significance
 Vernalisation-
Introduction
Site
requirement
mechanism
significance

3. PHOTOPERIODISM

4. INTRODUCTION
Photoperiodism is the phenomenon of physiological
changes that occur in plants in response to relative
length of day and night (i.e. photoperiod).
The response of the plants to the photoperiod,
expressed in the form of flowering is also called as
photoperiodism.
The phenomenon of photoperiodism was first
discovered by Garner and Allard (1920).

5. TYPES OF PHOTOPERIODISM
 Depending upon the
duration of photoperiod,
the plants are classified
into three categories.
 1. Short day plants (SDP)
 2. Long day plants (LDP)
 3. Day neutral plants
(DNP)

6. 1. SHORT DAY PLANTS
 These plants require a relatively short day light period
(usually 8-10 hours) and a continuous dark period of about
14-16 hours for subsequent flowering.
 These plants are also known as long-night plants.
 E.g. Rice, coffee, soybean, tobacco and chrysanthemum
 In short day plants, the dark period is critical and must be
continuous. If this dark period is interrupted with a brief
exposure of red light (660-665 nm wavelength), the short
day plant will not flower.

7. 2. LONG DAY PLANTS
 These plants require longer day light period (usually
14-16 hours) in a 24 hours cycle for subsequent
flowering.
 These plants are also called as short night plants.
 E.g. Wheat, radish, cabbage, sugar beet and spinach.
 In long day plants, light period is critical.
 A brief exposure of red light in the dark period or the
prolongation of light period stimulates flowering in long
day plants.

8. PATTERNS

9. 3. DAY NEUTRAL PLANTS
These plants flower in all photoperiod ranging
from 5 hours to 24 hours continuous exposure.
E.g. Tomato, cotton, sunflower, cucumber, peas
and certain varieties of tobacco.

11. INTERMEDIATE CATEGORIES OF PLANTS
i. Long short day plants
 These are short day plants but must be exposed
to long days during early periods of growth for
subsequent flowering. E.g. Bryophyllum.
ii. Short –long day plants
 These are long day plants but must be exposed
to short day during early periods of growth for
subsequent flowering. E.g. certain varieties of
wheat and rye.

12. PHOTORECEPTORS IN PHOTOPERIOD
 All photoreceptors contain an organic non-protein
component known as chromophore that serves as
the primary site of photon absorption (Möglich et al.
2010).
 At present, six classes of photoreceptors are
known: PHYs, cryptochromes (CRYs), light–
oxygen–voltage (LOV) sensors, blue light sensors
utilizing flavin adenine dinucleotide (FAD),
rhodopsins, and xanthopsins (Möglich et al. 2010).

17. SIGNIFICANCE OF PHOTOPERIODISM
hybridization experiments(florigenhormone).
Physiological preconditioning.
Increase yield
Plants remain vegetative for longer period
(radish,carrot,etc.)
Annuals can be grown twice or thrice a year.
Prevention of winter dormancy & autumn
leaf fall.
Strawberry-Increased stolon formation
through long days.

18. VERNALIZATION

19. INTRODUCTION
 It was found by Lysenko (1928), a Russian worker that
the cold requiring annual and biennial plants can be
made to flower in one growing season by providing low
temperature treatment to young plants or moistened
seeds.
 He called the effect of this chilling treatment as
vernalization. Vernalization is, therefore, a process of
shortening of the juvenile or vegetative phase and
hastening flowering by a previous cold treatment.
 Some plants require exposure to a low temperature , 0
to 10°C ,for few days to a few weeks for flowering.
such an induction of flowering by a low temperature is
called vernalisation

21. SITE FOR VERNALIZATION
The stimulus of
vernalization is
perceived only by
the meristematic
cells(active apical
meristem).
e.g.- shoot tip,
embryo tips, root
apex, developing
leaves, etc.

22. REQUIREMENTS OF VERNALIZATION
(i) Low Temperature:Low temperature
required for vernalization is usually 0°—5°.
(ii) Period of Low Temperature Treatment:It
varies from a few hours to a few days.
(iii) Actively Dividing Cells:
(iv) Water:
(v) Aerobic Respiration
(vi) Proper Nourishment.

23. MECHANISM OF VERNALIZATION
The stimulus received by the actively
dividing cells of shoot or embryo tip travels
to all parts of the plant and prepare it to
flower.
The stimulus has been named as vernalin.
It can be passed from one plant to another
through grafting in case of Henbane but not
in others.

24. Mechanism of Vernalization
Two theories
1. Phasic
development
hypothesis
2.hormonal
hypothesis.

25. Phasic development
hypothesis
thermostage photostage third stage

27. DEVERNALIZATION
The positive effect of the low temperature
treatment on the vernaliztaion of the plants can
be counteracted by subsequent high
temperature treatment. This is called
as devernalization.
The degree of devernalization decreases if the
duration of the cold treatment has been longer.
However, the devernalized plant can again be
vernalized by subsequent low temperature
treatment.

28. IMPORTANCE OF VERNALIZATION
Induces early flowering there by shortening the
vegetative period of the plants(production of
more than one crop in a year).
The winter variety crops can be converted
to spring variety(Protection from freezing
injury).
It helps in increasing the yield of the plants.
It helps in inducing the resistance to number of
disease.
Tropical plants (requiring long summer) can be
grown in temperate areas(short summer).

29. CONCLUSION

30. THANK YOU