Juvenility and flower bud differentiation

Juvenility and flower bud differentiation

1. Juvenility

+ A seedling passes through different stages in its life
cycle. These stages are embryonic growth, juvenilit,
maturity, senescence, and death.

Juvenility is a developmental stage in seedling
plants during which it is unable to induce flowers.

The length of juvenility varies between plants. The
annuals have short and perennial have long
juvenile period.

2. Table - Juvenile period of some plants

Plant Juvenile period
E 7 20-30 days

5-10 year

A <5 cys
1 year
Tomato, brinjal 60 days

80 days

3. Characteristics of Juvenility %
Leaf Form- Leaf gorous in juvenile phase. Lew
morphology also differ in juvenile phase of some plants
like Acacia sp.

Growth Form - Juvenile shoot growth appears whip
like. The shoot grows parallel to main stem, Such

shoots are known as water sprout, e. g. Citrus, Guava
etc.

Presence of thorns- Some fruit plant seedlings show
thorns in juvenile phase and these thorns disappears
when attain adult phase. Example- Apple, Pear, Citrus
etc.

4. Leaf Retention - In juvenile phase plant do not fk
leaves throughout the year. Whereas, it falls in adult
phase or maturation phase.

Root emergence - In propagation use juvenile phase
plant parts the root emergence faster then mature

portion of plant.

5. Bud- A bud is an immature shoot stem which

often surrounded by protective scale leaves. The bud
develops into a lateral branch, a flower or an
inflorescence. These buds develop into flower or

inflorescence is much desire aspect in fruit
production. The development stages in flowering is as
under-

6. 1.Flower bud differentiation- It is also known as
flower induction. For bud differentiation to occur
there is enhanced cell division in the central zone
below the apical part of the meristem. Due to cell
division, there is differentiation of parenchyma cells

which surround the meristem, into flower primordia.
2.Initiation - In initiation of flower formation

7. It includes length of time fre ak
induction to bloom. During this period the flower is generauy
receptive to pollination. Opening of flower (anthesis) is the final
tage of development

A flower is a modified reproductive shoot, basically a stem with
an apical meristem that gives rise to leaf primordia.

8. Table - flower bud differentiation and flowering i
some important fruit crops

Fruit Crop Bud differentiation | Flower opening

Apple June-July Next spring

Peach June July Next spring

Pear July August Next Spring

[ES october Next spring

9. Types of Bud

1.Simple Bud- It grows into vegetative shoot. It is
also known as leaf bud.

2.Mixed Bud - It grows into a shoot with a flower
is also known as flower bud.

3.Compound Bud - It grows into both leave

10. Factors influencing flower bud differentiation

1.Endogenous factors

a)Carbon: Nitrogen ratio (C:N ratio) - High ratio of
carbohydrates to nitrogen favours flowering. In young plant,
heavy application of nitrogen which lowers C:N ratio delays
flowering. The plant which are old, weak and having higher
C/N ratio flowers heavily. With rı to C/N ratio, there

may be four situations, such as:

i) High nitrogen and low carbohydrates - flower forms

iiJHigh nitrogen and enough carbohydrates - flower form

iii)Moderate nitrogen as well as carbohydrates - Good growth
and abundant flower formation

iv)Low nitrogen and high carbohydrades - Formation of only
few buds

11. ok
b) Genes - When plants undergo phasic change from juven.?
to adults, eafl gene synthesizes. The gene is responsible for
truncating juvenile and adult phases which induces early
flowering. The HST(HASTY) gene promotes juvenility in plants.

12. 2. Environmental factor

‘Temperature

Temperature is main environmental factor which is associated

with flowering. Due to availability of a particular temperature in
ring season, flowering occurs at the same time each year

Exposure of plants to low temperature favours flowering,

Biennial plants like carrot, celery, cauliflower, cabbage, turnip

etc. upto exposed to 0 to 10°C temperature come into flowering
This is known as vernalization. In these plants, low
temperature requirement is commonly known as chilling
requirement. They have chilling requirement below 7° C for
about 4-60 days for the bud to bloom in spring

13. Photoperiod Ae

Some plants flowering only when their photoperiodic

requirement is fulfilled. According to photoperiod plants are

categorised into three broad categories as under :-

1)Long day plant (LDP): - flowering occurs only if day length
is 12 hrs or more than hi

2)Short day plant (SDP): - In these plants flowering occurs
when day length is less than 12 hr:

3)Day Neutral Plant (DNP): - In these plants flowering is not
regulated by day length.

14. Light

Light intensity, duration as well as quality
bud differenti wering. Pl

light intensity flowers properly than low
That’s why outer fruit tree branches have mor
than the inner ones.

The red light (Sunlight) p
red light inhibits. So, quality of light also affects the
flowering.

15. 3. Managemental Factor
i)Nutrients - nutrients decide vegetative or
reproductive growth of the plant. Nitrogen increases
the vegetative growth of the plant. And it favours the
carbohydrates utilization of the plant. Phosphorus
in plant as protein synthesis, cell division;

potash in translocation of sugar. Other nutrients
also involve in flowering and bud differentiation.

ii) Moisture - Non availability of moisture ex
time of flower bud differentiation. Flower primordia
is less in water deficit conditions.