By-Vijaylaxmi UK

2. KITTUR RANI CHENNAMMA COLLEGE OF
HORTICULTURE, ARABHAVI
GROWTH AND DEVELOPMENT OF FRUIT CROPS
FSC-504 (2+1)
PRESENTED BY:
Vijaylaxmi U K
Jr. Msc

3.  The first step of sexual
reproduction.
 Most important in plant
breeding.
 One of the most dramatic
events in the ontogeny of
a plant.
 Flowering leads to an
exciting succession of
events like anthesis, fruit
set, fruit development,
maturation and ripening.
Flowering

4. Flower Morphology
Flower
Reproductive part of the plant.
A flower is a metamorphosed shoot meant
especially for the reproduction of the plant.
Floral parts
1.Sepals
2.Petals
3.Stamen
4.Pistil
5.Receptacle

5. Diagram of a typical flower

6. Physiology Of
Flowering

7. Flowering
 Transitional phase in the life cycle of a
plant.
 Immense importance for perpetuation
& origin of variability in the next
generation.
 Takes place by the transformation of
vegetative apex into a reproductive
structure.
 The change from the vegetative state
to the reproductive state.

8.  Shoot meristem is reduced to develop
sepals, petals, stamens, stigma etc.. .
in case of leaves.
 The plant must attain specific state of
“Ripeness to response” before it
flowers.
 Once the stage is reached, then it can
induce to flower.

9. a. Irreversible changes in which apical
bud changes its vegetative phase to
reproductive phase.
b. Improper conditions causing flower
buds to abort are
1. High temp
2. Moisture stress
c. Flowering can be induced naturally
or through PGR (plant growth
regulators).
Flower Initiation and Development

10. Factors influencing the transformation
of the juvenile phase into the mature
phase:
1. Temperature – Vernalization
2. Photoperiodism
3. Drought stress
4. Low fertility levels
5. Hormonal balance.

11. 11
Flower Production
Four genetically regulated pathways to
flowering have been identified.
1. The light-dependent pathway
2. The temperature-dependent
pathway
3. The gibberellin-dependent pathway
4. The autonomous pathway.
Plants can rely primarily on one
pathway, but all four pathways can be
present.

13. 13

14. Physiology of flowering
It involves two steps.
1. Events in the bud leading to flowering:
a. Induction:
-flowering stimulus is generated.
-Influenced by water stress, chilling temperature or
photoperiod.
b. Evocation:
-shoot apical has received floral stimulus and
irreversibly committed to form flower bud
primordia.
c. Initiation:
-evoked bud becomes recognizable as a flower bud
and is thus committed to reproductive
development.
-broadening and flattening of the growing points.

15. 2. Differentiation of the growing points:
 Increase in synthesis of DNA and RNA.
 Frequency of cell division within the
central zone of shoot apical meristems is
increased.
 Shoot meristem is induced to develop
sepals, petals, stamens and carpals in
case of leaves.
 The flat apical meristem becomes
domed.
 The meristem becomes a block like
structure.
 The subsequent development of flower
meristem is relatively rapid.

16. The plants in order to flower require
a certain day length i.e., the relative
length of day and night which is called
as photoperiod.
The response of plants to the
photoperiod expressed in the form of
flowering is called as photoperiodism.
Photoperiodism

17. 1. Julien Tournois (1910) – 1st found about Long
Day in flowering.
2. George Klebs (1918) – observe the function of
Long Day in flowering.
3. Garner & Allard (1920) –found photoperiod
⇨relative duration of light and dark towards
control flowering of certain crops.
eg: Tobacco – flowering once expose to short light
period (SDP).
Hence it has been concluded that the relative
length of the day is a prime factor in
flowering of plants.
4. Hamner & Bonner (1938) – Dark time has more
function in determining the reaction in
photoperiod.
History of photoperiodism

18. Control of flowering
Flowering
“Florigen”
hormone
Flower buds
Photoperiod mechanism
in the leaves
Change in day length

19. 19
Depending upon the duration of the
photoperiod, plants are classified into 3
categories.
18 hours

20. Short and Long Day Plants
Flowering


21. 1. Short Day Plants (SDP):
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.
oThese plants are also known as long-night-
plants.
Eg. Chrysanthemums, straw berry, coffee, pineapple
etc…
o In short day plants the dark period is critical and
must be continuous. If this dark period is
interrupted even with a brief exposure of red light

22. 22

23. 2. Long day plants (LDP):
These plants require a longer day light
period (usually 14-16 hours) in a 24 hours cycle
for subsequent flowering.
Also called as short night plants.
 Eg: Apple, passion fruit etc..
 In long day plants the light period is critical.
The prolongation of the light period stimulates
flowering in long day plants.

24. 24

25. 3. Day neutral plant (DNP):
Without critical day length, they can flower in
any day length of 24hr cycle, if other
conditions are satisfied.
eg. Banana, guava, tomato, brinjal etc…
Critical Day Period
 It is the duration of the photoperiod or the
dark period that ultimately determines
whether the plant has to go through
vegetative growth or to produce flowers.
 Referred as the day length of 24hr cycle -
the shortest day length for LDP flower and
the longest day length for SDP flower.

26. K. Hamner and J. Bonner in 1938

27. Long Short Day Plants:
These are short day plants but must be
exposed to long days during early periods
of growth for subsequent flowering.
Eg : species of Bryophyllum, night jasmine
etc..
Short-Long Day Plants:
These are long day plants but must be
exposed to short days during early periods
of growth for subsequent flowering.
gs: Wheat (Triticum), Rye (Secale),
perennial temperate grass etc…

28. Initiation of flowering in a plant after
exposure of light for a required period of
time.
It is calculated for a 24hrs.
The time of specific exposure to light
within a day is called as photoinductive
cycle.
The number of these cycle may be 1 or 2
or more depending on plant species and
together they are called photoinduction.
Photoperiodic induction

29. It is a biological, proteinaceous pigment that
absorbs light.
It is a non photosynthetic, photoreceptor
pigment.
Mature leaves are the site of production of
these stimulus.
 Two types :
i) Red light absorbing form which is designated
as PR
ii) Far-red absorbing form which is designated
as PFR.
Phytochrome

30. What Is Phytochrome ?
Phytochrome is a pigment found in some plant cells that
has been proven to control plant development.
 This pigment has two forms or “phases”. P-red light
sensitive (Pr) and P –far red light sensitive (Pfr) forms.
The actual plant response is very specific to each species
and some plants do not respond at all.

31. When PR form of the pigment absorbs
red light (660-665 nm), it is converted
into PFR form.
When PFR form of the pigment
absorbs far-red light (730-735 nm)
converted in to PR form.
The PFR form of the pigment
gradually changes into PR form in dark.

32. 32

34. H. A. Borthwick and S. B. Hendricks 1950

35. * Plants measure the ratio of Pfr/Pr.
 LDP would flower when the ratio is high.
 SDP would flower when the ratio is low.
 Since Pfr is liable to change and is
broken down at night it reverts back
to Pr.
 The longer the night, the lower the
phytochrome (Pfr) content.
 The relative amount of Pfr remaining
at the end of the night would be an
indication of the day length.

36. Flowering in SDP:
◦ Short day plants flower when the night period is
long.
◦ In day light or red light, phytochrome red (Pr) is
converted to phytochrome far red (Pfr). The
conversion actually only requires a brief
exposure to white or red light.
◦ In the dark, Pfr is slowly converted back to Pr.
◦ A long night means that there is a long time for
the conversion.
◦ Under short day conditions (long night) at the
end of the night period the concentration of Pfr is
low.
◦ In SDP, low Pfr concentration is the trigger for
flowering.

37. (Fast)
Dark
Reversion
Red Light
740 nm660 nm
Pr
Pfr
(Slow)
Far Red Light
Synthesis Destruction
Vegetative
(Non-
Flowering)
Reproductive
(Flowering)
Mid-Summer
Sunlight
Short-Day Plants Need
Low Pfr to Bloom!

38. In the short-day plant
PFR PR builds up
Darkness (slow)
Short-day
plants
FLORIGEN
Activated
FLOWERING

39. Flowering in LDP:
◦ Long day plants flower when the night
period is short.
◦ In day light (white or red) the Pr is
converted to Pfr.
◦ During periods when the day light period
is long but critically the dark period is
short, Pfr does not have long to
breakdown in the dark. There is a higher
concentration of Pfr.
◦ In LDP, high Pfr concentration is the
trigger for flowering.

40. (Fast)
Dark
Reversion
Red Light
740 nm660 nm
Pr
Pfr
(Slow)
Far Red Light
Synthesis
Destruction
Vegetative
(Non-Flowering)
Reproductive
(Flowering)
Mid-Summer
Sunlight
Long-Day Plants Need
Low Pr to Bloom!

41. In the long-day plant
PFR builds up PR
Sunlight
Red light
Long-day
plants
FLOWERING
FLORIGEN
Activated

42. ◦ Dark period (length of night is called as Nycto
period) more important in photoperiodism
reaction because interruption during night will
inhibit flowering in SDP but promote flowering in
LDP.
◦ Dark interrupted by short exposure of light
results in flowering in long day plants. But if
light period is interrupted by dark exposure has
no effect on flowering.
◦ In short day plants, Pr promotes flowering when
Pfr suppresses it, when it is vice versa in long
day plants.

43. Importance of photoperiodism
 Annuals can be grown twice or thrice
in a year.
 Prevention of winter dormancy and
autumn leaf fall.
 Increased stolon formation through
long days in Strawberry.
 Plants like radish, carrot etc..can be
made to remain vegetative for longer
period.
 Yield can be increased.

44. Photoperiodism and flowering in
fruit crops
 Mango: Flower induction is caused by cool
temperature and not by short photoperiods
and flowering is inhibited by warm
temperature and not by long photoperiods.
 Strawberry: Flower formation is influenced
by the duration of length of daily light
period. Short days induce flower
production.
 Papaya: Long day and high temperature
promote female flower production where as
short day and low temperature promote
male flower production.

45.  Pineapple: Neither a diurnal temperature
nor short days are necessary for natural
flowering.
 Guava: There is no quantitative involvement
of photoperiod in flowering as it is a day
neutral plant.
 Passion fruit : Artificial light or long days
increase the flowering but number of
flowers are reduced in shaded treatment.
 In fruit crops like peaches, plums and
cherries, floral initiation appears to be
unaffected by photoperiod.

46. Summary
Sunlight
Red light
Darkness (slow)
Far red light
(fast)
PFR builds
up
Long-day
plants
FLOWERING
FLORIGEN
Activated
PR builds
up
Short-day
plants
FLORIGEN
Activated
FLOWERING

47. References
Fruit Tree Physiology
W S Dhillon, Z A Bhat
Physiology Of Crop Plants
Franklin Gardener

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