1. The document discusses the different growth stages of plants including juvenile, transitional, mature, reproductive, and senescence stages. 2. It provides details on the juvenile stage, including that plants are vegetative and unable to flower during this phase, and examples of morphological differences between juvenile and adult forms. 3. The transitional stage is described as having characteristics of both juvenile and mature tissue and involving the transition from vegetative to floral meristems.

1. Dr. Mahmoud Abd El-Hakeem
Dept. of Horticulture
Fac. of Agriculture
Minia University
Flowering Physiology
HOR 660
Part I

2. A plant pass through its growth on different phases:
(1)juvenile– in which it will not flower
(2)Transitional stage Have both juvenile and mature
tissue
(3) Mature– in which appropriate environmental stimuli will
evoke flowering
(4) Reproductive– in which flowering actually takes place.
(5) Senescence stage The final stage in a plant’s life
cycle
Plant Growth Stages

4.  Vegetative growth and unable to flower even if plant grows an
environment for flowering
 a physiological state of plant before flower differentiation
 Flowering cannot be induced
 plants often differ in appearance from the adult.
 Phase length varies:
 annual – shorter eg. Weed will be at juvenile stage 4-5 d after
germinated
perennial – longer at juvenile stage
eg. in certain trees up to 40 years
 Morphologies:
 Simple primary leaf to trifoliate leaves
 beans: adult – compound leaf; juvenile – simple leaf
 leaves lobe
 rapid growth
Usually, the basal part of tree is juvenility and the top is mature or adult
in physiology.
Juvenile stage

5. 1. Long-day treatment - shorten the juvenility
form 5 ～ 10 year to 1 year of birch
2. Grafting- speed up flowering of fruit crops
in 2-3 year.
3. GAs treatments- can induce flowering in
juvenility of ivy, cypress and fir.
Methods to shorten juvenility

6.  Have both juvenile and mature tissue
 May revert back to juvenile if environmental
conditions are right.
 Involves the transition of a vegetative
meristem, producing leaves and stems, into a
floral meristem, producing flowers.
Transitional stage

9. JUVENILE AND ADULT FORMS OF ENGLISH IVY
(Hedera helix)
ADULT
JUVENILE
(gibberellin
causes reversion
of adult form to
juvenile form in
english ivy)

10.  Stage where plants are ready to flower.
 Flowering - ultimate expression of mature state
 Changes influence by environment
 Environment serve as expression changes regulator
 Changes in physiology and morphology
 Transformation of primodium of stem, leaf or
vegetative part to primodium reproductive organ
 One way transformation
Many plants produce flowers independent of
environmental conditions
Maturity or reproductive stage

14.  Flowering occurs as a result of a reprogramming of the
development of the SAM. Rather than initiating stems,
leaves and axillary buds, a reproductive (or floral) meristem
gives rise to an inflorescence, i.e. flowers The sharpness of the transitions between each phase, their
duration, and the extent to which these phases can coexist
within regions of a single plant vary very widely between
species

15. The final stage in a plant’s life cycle
a. May occur naturally or accelerated by environmental
conditions including pathogenic attack
b. Cell and tissues deteriorate
c. Partial senescence is when plant organs age and
eventually die
d. Complete senescence is when the whole plant dies.
Monocarpic plant – flowering and fruiting once
Polycarpic plant – many times/repeat
Senescens

16. Flowering

17. Perennial plants
Able to flower and fruit for an indefinite number of growing seasons
- may be herbaceous or woody
-in deciduous plants all the leaves fall, and the tree is bare, at a
particular time of year
-in evergreen plants, the leaves drop throughout the year, and so
the plant is never completely bare
Annual plants
Grow, and flower and typically die within one growing season
- usually herbaceous
Biennial plants
Have two-year life cycles
-they store energy the first year and flower the second year
In relation to flowering and fruiting or duration of plant life,
plants are group into:

18. THE CONTROL OF FLOWERING
 Plants flower at different times of the year.Plants flower at different times of the year.
 How do plants keep track of the seasons?How do plants keep track of the seasons?
 Which environmental signals control flowering?Which environmental signals control flowering?
 How do environmental signals bring about theHow do environmental signals bring about the
transition to flowering?transition to flowering?
Floral induction is regulated by different endogenous and
environmental signals which, together, cause flowering at
an appropriate time.

19.  Irreversible change in which bud (meristem)
changes from growing vegetative tissue to
reproductive tissue
 Improper conditions can cause flower buds to
abort
1. High temp
2. Moisture stress
 Flowers can be induced naturally or through
PGR (plant growth regulators)
Flower Initiation and Development

22. Germination
Juvenile
Adult
Adult
Eucalyptus Juvenile vs Adult Leaves
Juvenile Vegetative
Reproductive

23. The terminology of floral evocation
The events occurring in the shoot apex that specifically
commit the apical meristem to produce flowers
Floral evocation: The processes whereby events in a shoot meristem
are altered in such a way to produce flowers as opposed to leaves.
Floral induction: The actual signal that results in evocation.
Flower initiation: Formation of flower buds after induction.
Flower development: The process after flower initiation until anthesis.
Anthesis: The shedding of pollen by the stamen.
It should be noted that flower opening (petal unfolding) can occur prior
to, during, or after anthesis.

24.  Competent: A meristem can respond, in the expected manner, when
given an appropriate developmental signal to flower.
 Determined: If a meristem follows the same developmental program
even after it is removed from a source of environmental or
biochemical stimulus
 In some cases the ‘expression’ of flowering can be delayed until a
second developmental signal is received.
 Some species require a cold temperature treatment followed by a
specific photoperiod for successful evocation.

25. Floral evocation: competence and
determination

26. Time transition to flowering so that reproduction occurs at
appropriate time of year.
Spring/Summer-type annuals:
vernalization has no effect.
Winter-type annuals: vernalization
decreases time to flowering.
Biennials: require vernalization to
flower.

27.  Whatever combination of environmental cues and
internal signals is necessary for flowering to occur,
the outcome is the transition of a bud’s meristem
from a vegetative state to a flowering state.
This requires that meristem-identity genes that specify
that the bud will form a flower must be switched on.
Then, organ-identity genes that specify the spatial
organization of floral organs - sepals, petals, stamens,
and carpels - are activated in the appropriate regions of
the meristem.
Identification of the genes and the internal and external
signals that regulate them are active areas of research.

29. Factors influence transformation of the juvenile
into the mature:
1.Temperature – Vernalization
2.Photoperiodism
3.Light intensity
4.Drought stress
5.Low fertility levels (especially N)

30.  Klebs (1918) – ratio of carbohydrate with inorganic
nutrient esp N (C:N) high – will promote flowering
 Kraus & Kraybill (US) – flowering on tomato plants was
controlled by CHO:N level
 CHO:N low – delay flowering & less flower (N high)
 CHO low, N low – less vegetative part, less flower
 CHO:N high – faster and no of flower increase
 there is no C:N critical for flowering
Nutrition

31. Vegetative vs. Flowering shoot apex in arabidopsis
Vegetative apex flowering apex

32. 33
Flower Production
 Flowering Signal
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 (environment/endogenous
pathway
Plants can rely primarily on one pathway, but all
four pathways can be present

33.  Floral stimulus production
Following inducing signal flowering
switch to turn on florigen
 Site of flowering
commitment
shoot apex: require sufficient
amount of floral stimulus for
continuous flower production
leaf: commit to continuously

35.  Many species do not require a precise set of environmental stimuli
and will flower under almost any conditions compatible with
continuing growth

36. Plant size and flowering
 Variation in the ages at which species first flower can be
attributed to differences in the length of the juvenile
period.
 Many plants which grow at lower latitudes (seasonal
variation in day length and temperature is much less
marked), flower only once they have attained a certain
size.
 In many varieties of tobacco the SAM becomes
committed to flowering only once a certain number of
phytomers (internodes with their leaves) have been
produced.
 The precise number depends upon the variety examined
but is typically near 35.

37.  If the top of the tobacco plant is removed and re-rooted prior to this
point, it will continue to grow in a vegetative manner until the
appropriate number of nodes have been produced.
 The SAM is said to be indeterminate, as the fate of the cells within
it is not fixed. It can, be maintained in the vegetative state
indefinitely if continually removed rerooted.
 Once the plant has attained a certain size, the SAM becomes
committed to flower and its fate is now determined.
 If the top of the plant is removed and re-rooted only a few
vegetative nodes will be produced prior to flowering.
 The signals which cause this reprogramming of SAM development
are not known but include transmissible signals produced in the
leaves.

38. Juvenile period lengths (leaf number at which plants
become competent to flower) for various herbaceous
plants

39. 40
Autonomous Pathway--Plants Can Count
-Tobacco plants produce a uniform number of nodes before flowering
Upper axillary buds of flowering tobacco remember their
position if rooted or grafted

40. Shoot removed here
Shoot Florally Determined Shoot Not Florally Determined
a. b.
Intact plant
Shoot
removed
Rooted shoot Flowering
rooted shoot
Intact plant
Shoot
removed
Rooted shoot Flowering
rooted shoot
Autonomous Pathway--Plants Can Remember
Shoot removed here
Not-Florally Determined Plants are said not to remember...Florally
Determined plants are said to remember

41. Commitment to flowering in tobacco Wisconsin 38 is controlled by the
number of phytomers. The plant becomes committed to flowering only
once a specific number of phytomers have been produced. If the top of
the plant is removed and re-rooted before this number is reached (A),
vegetative growth continues. If the procedure occurs after this threshold
has been exceeded (B), a few further vegetative phytomers develop and
then flowering occurs.

42. A fate map of the maize (Zea mays)
shoot meristem at the mature embryo
stage. (A) A diagram of the maize shoot
meristem. At this stage leaf 6 is just
about to be initiated and leaf 5 is a
small primordium. There are no clearly
defined boundaries within upper tassel
the shoot, hence the domains tassel
branches indicated are only
approximate.
Nodes to which cells in each domain
typically contribute are indicated.
(B) A mature maize plant showing 5
leaves and tassels.

43.  In maize the fate of the cells within the SAM is determined
during embryogenesis.
 The SAM is formed together with 4–5 embryonic vegetative
leaves.
 As the plant develops it will produce between 16 and 22
nodes (depending upon the variety) before a tassel is
produced.

44.  The tassel consists of hundreds of closely packed nodes
bearing clusters of flowers.
 It is possible to map the fate of different regions of the SAM
whilst still within the embryo, although the fate of individual
cells is not fixed.
 It is possible to make a maize plant produce twice as many
vegetative nodes by removing the shoot apices and growing
them in culture for a time.
 This extra vegetative growth results from cells in the upper
region of the SAM, which would normally develop as the base
of the tassel, now developing as vegetative nodes.
 There has been no extra production of nodes, rather the fate of
a few existing nodes has been altered.

45. 46
Autonomous Pathway
The autonomous pathway does not depend on
external cues except for basic nutrition
It allows day-neutral plants to “count” nodes and
“remember” node location

47. THE ABC MODEL FOR FLORAL
ORGAN IDENTITY

51. The ABC model of floral development and homeotic mutations of
Arabidopsis flowers wild-type and single-gene homeotic mutations.

52. The ABC model accurately predicts the pattern of organs observed in double
and triple mutants. In the absence of A, B and C activities, whorls of leaf-like
organs are produced.
Homeotic mutants
)homeo = like(

53. Mutations in floral organ identity genes

54. Quadruple mutant (ap1, ap2, ap3/pi, ag) results in the production of
leaf-like structures in place of floral organs

56.  In the vegetative period, the internodes of Arabidopsis are very
short, leading to the rosette growth habit.
 During early reproductive development, the SAM becomes an
inflorescence meristem which produces a few cauline leaves
and phytomers with much longer internodes.
 Floral meristems are borne on the flanks of the inflorescence
meristem and develop to form the flowers.
 Later, secondary inflorescences develop which also bear
flowers. The regulation of inflorescence and floral development
is controlled by a complex network of interacting genes.
The development of the inflorescence

57. (A) The plant produces leaves in a
rosette during vegetative
growth. When reproductive
growth is initiated, the
internodes elongate to form
the stem of the primary
inflorescence on which
secondary inflorescences
develop.
(B) Cauline leaves and flowers are
borne on the inflorescence.
(B) A close-up of the apex of an
inflorescence. Flowers at
different stages of
development can be seen at
the apex. Arabidopsis thaliana in flower

58. FLOWERING INFLOWERING IN ARABIDOPSISARABIDOPSIS)B
(

59.  In the wild-type plant a primary inflorescence, bearing cauline leaves and
flowers, emerges from the rosette. Secondary inflorescences also develop.
 In the leafy mutant more secondary inflorescences develop and flowers are
leaf-like.
 The leafy apetala1 double mutant produces few or no flowers and all the
axillary buds on the primary inflorescence develop as secondary
inflorescences. In the terminal flower mutant, inflorescence development is
limited as the meristems differentiate to produce flowers
Mutations affecting
reproductive development
in Arabidopsis thaliana

60.  The falsiflora mutant of tomato
 (A and B) wild-type tomato, flowers develop on inflorescences, I,
borne on the main stem and leaves, L, continue to be produced.
 (C) In the falsiflora mutant, flowers are replaced by secondary
inflorescence shoots and leaves; arrows indicate where some shoots
have been removed for clarity.
 (D) A close-up of an inflorescence of the falsiflora mutant, showing
the conversion of flowers into shoots and leaves; secondary
inflorescence shoots, IS, have been removed for clarity.
 In the accompanying diagrams, shoots which will continue to
produce leaves are shown as lines with arrowheads; flowers are
shown as circles. From

61. The falsiflora mutant of tomato
)A and B( wild-type tomato,
flowers are replaced by
secondary inflorescence
conversion of flowers into shoots and leaves

62. Inflorescence and flowers
of Antirrhinum majus.
(A)Flowers are borne on
an inflorescence.
(B)The wild-type flower
exhibits bilateral
symmetry.
(C) Mutations in the
cycloidea variety result in
the development of
radially symmetrical
flowers.

63. he model to ABC)DE( in which D function controls ovule developmen
and E function ) SEP ,EPALLATA family genes( encodes co-factors
of A, B, and C floral organ identity genes

64. flowers of Vinca minor . )A, B( Wild-type. )C–F( Spectrum of floral phenotypes of the
flore pleno variety )C, E and F photographed after transplantation into a garden( with an
extra )inner( whorl of petals visible in )D( and )E(. In )F(, a stalked second flower arises
from within the flower. Abbreviations: s , sepal; p, petal; ip, extra )inner( petals; if, stalked
flower within flowe

65. Floral diagram of V. minor wild-type )A( and flore pleno )B( flowers. Note that the
diagram of the mutant flower is just one example among the range of phenotypes
detected. Sepals are shown in dark green; petals in blue and purple, respectively;
stamens in yellow and the gynoecium in pale green. Stamens that are partly
transformed into petals are shown in purple that runs into yellow