This document discusses various methods for manipulating flowering in forest trees, including floral induction and prevention of flowering. It describes floral induction as the onset of flower development, and lists methods like manipulating growth environment (temperature, photoperiod, nutrition, stress), chemical methods (gibberellins, cytokinins, ethylene), and transferring flower-inducing genes. Prevention of flowering can be achieved through physical ablation of floral tissues or suppressing essential flowering genes. Manipulating flowering allows for more rapid breeding of trees.

1. Name : Nisar Ahmad Mir
Degree : M.Sc Forestry
Division : Forest Biology & Tree Improvement
Course No. : FOR-591 (0+1)
Seminar Incharge :
Date : 03/08/2021
Credit Seminar
Sher-e-Kashmir
University of Agricultural Sciences & Technology of Kashmir

3. INTRODUCTION
A flower is the
reproductive structure of
plants.
Flowering is the
expression of many processes
involving the initiation,
differentiation, and growth of
the flower.

4. Action of influencing
or controlling the flowering
In forest trees, manipulation is
mainly done through;
Floral induction
Prevention of flowering
Manipulation of Flowering

5. Refers to the first stage of
flowering, or the onset of flower
development, where the floral
buds of a plant become
identifiable/start to form
Floral induction

6. Methods by which flowering can be
induced are:
Manipulation of growth
environment
Chemical methods
Physical methods
Transfer of flower inducing
genes
Floral induction

7. Manipulation of growth environment
Growth environment can
be manipulated by:
Temperature
Photoperiod
Nutritional status
Stress
In vitro culture

8. Changes in both diurnal variation and overall
daily mean temperatures have been associated with
enhanced flower initiation.
Flower initiation in the West African timber tree
Triplochiton scleroxylon K.Schum has been
associated with changing temperatures. Potted
plants were found to flower when transferred from
a warmer (30°C) to a cooler (20°C) glasshouse and
watered with cold water. (Leakey et al., 2001)
Temperature

9. Defined as day length or ‘the period
of daily illumination received by a tree
Long day plants
Short day plants
Day neutral plants
Changing photoperiod enhances
flowering
Eucalyptus plants grown under 8-
10 h flowered sooner and produced
more than twice as many flowers as
those grown under 16-19.5 h. Longman
et al. 1997.
Photoperiod
Flowering in Arabidopsis is promoted by long-day
conditions. (left; 10 h light, 14 h dark) (right; 16 h
light, 8 h dark). Maarten et al., 2001

10. Improved mineral nutrition is often
considered as a flower-inducing treatment.
The endogenous carbohydrate status
plays an important role in the control of
floral induction in trees.
Treatments that elevate carbohydrate
levels promoted flowering, especially in
plants propagated vegetatively from scions
of mature plants ( Zimmerman et al., 1996).
Nutritional status

11. Defined by Lichtenthaler (1996) as
'any unfavourable condition or
substance that affects or blocks a
plant's metabolism, growth or
development‘
Abiotic stress
Biotic stress
Triggers floral induction
Hot, dry summers have been found
to induce flowering in both conifers
and broadleaf species (Philipson 2005).
Stress

12. Stress factor Species Flowering response
High-intensity light Picea mariana Induction
Low-intensity light Pinus banksiana Induction
Pseudotsuga menziesii Induction
Ultraviolet C Arabidopsis thaliana Induction
Drought Pseudotsuga menziesii Induction
Pinus banksiana Induction
Lemon Induction
Ipomoea batatas Promotion
Poor nutrition Picea mariana Induction
Pinus taeda Promotion
Thuja occidentalis Promotion
Ipomoea batatas Promotion
Arabidopsis thaliana Induction
Poor nitrogen Pinus banksiana Induction
Poor oxygen Picea mariana Induction
Kaede & Kiyotoshi, 2010
Stress

13. In vitro culture
Uses nutritive culture media and
controlled aseptic conditions for the
growth of plant cells, tissues and
organs.
The plantlets can be incubated in
a sterile, controlled environment,
which can reduce interference from
biotic and abiotic stresses and
uncontrolled pollination.
Flowering can be induced when
desired

14. Flowering of Woody Bamboo in Tissue Culture Systems
In vitro florets are observed to
have both androecium (consisting of
six stamens) and gynoecium.
The pollen fertility determined
by staining with Acetocarmine stain
in in vivo flowering was 63% and
41% in in vitro flowering
Nadgauda, et al. 1997

15. The chemicals by which
flowering can be induced
are:
Gibberlins
Cytokinins
Ethylene
Growth retardants

16. Gibberellins (GAs) are a large
family of tetracyclic diterpenoid
plant hormones.
Promotion of cell division
and elongation
Seed germination
Stem elongation,
Root growth
Flowering induction
(Daviere et al. 2008)
Species Application Effects
Black spruce Stem Injection Increased CFB
Douglas fir Stem injection Increased CFB
Jack pine Foliar spray Increased MFB
Loblolly pine Stem injection Increased CFB

17. (Daviere et al. 2008)
Cytokinins are
plant hormones that
influence growth and the
stimulation of cell division.
Important for cell
differentiation
They have been found
to induce flowering

18. Ethylene is regarded as a
multifunctional phytohormone
that regulates both growth, and
senescence.
Fruit ripening
Seed germination
Has been used to induce
flowering in conifers.
(Maverick et al. 2010)

19. Compounds used to reduce the
shoot length of plants in a desired
way without changing
developmental patterns or being
phytotoxic.
Chlormequat chloride
Pyrimidines such as ancymidol
and flurprimidol
Triazoles, like paclobutrazol
and uniconazole
(Berova and Zlatev 2000)

20. One of the most common growth
retardants used in plants
PBZ has antagonistic effects against
plant hormone gibberellin
Reduces internodal growth
Increases root growth
Improves the concentration of
photosynthetic pigments, minerals, and
carbohydrates.
Highly involved in inducing flowering
(Berova and Zlatev 2000)

21. Vascular restrictions
Root growth control
Confinement and root pruning
Shoot training

22. The most common ways in
which vascular movement has
been impeded are;
Girdling
Wire girdling
Root growth control

23. Also called ring-barking,
Girdling increased
production of seed cone and
pollen cone buds in Douglas fir
from 79 and 4500 to 325 and
9,300 respectively.
Theodore , et al. 1997

24. Less severe than complete girdling,
Used to stimulate flowering in
conifers
Overlapping girdles in conjuction
with hormone treatment have been
even more successful in flower
induction in conifers.
Jing Zhang, 2008.

25. Involves encircling selected
branches or the main stem with a
steel wire, which is twisted
“tightly”.
Wire girdling has been
successful in stimulatating
flowering in aspen.
Greenwood and Schmidtling 2003.

26. Root growth can be
controlled by :
Trickle irrigation
Fertigation

27. Effect of giberellic acid (GA4/7) and girdling on
induction of reproductive structures in Pinus patula
Method:
Partial stem girdling was done at the base of
the trunk and the GA4/7 solution was injected
into the xylem above the point of girdling.
Result:
Application of 1.27 mg/cm² GA4/7 and stem
girdling in July promoted the highest
percentage of trees with strobili, and increased
25 fold the number of female strobili and 5 fold
the number of male strobili per tree as
compared to the control treatment.
Jesus, v. et al., 2016

28. Floral-meristem-identity genes
LEAFY (LFY), involved in controlling the transition
from an apical meristem to a floral meristem
APETALA1 (AP1), required for sepal and petal
development (Weigel et al. 1992).
FLOWERING LOCUS T (FT), stimulates flowering
in Populus deltoides. (Rottmann et al., 2000)
When the Arabidopsis-derived LFY gene is expressed
constitutively in hybrid aspen (Populus tremula*P.
tremuloides.), it flowered in vitro within 7 months
instead of 8- 20 years
Nilsson and Weigel, 2005

29. Flowering does not begin for one to
several years
To speed flowering, transformation of an
Eucalyptus grandis with a variety of
constructs that enable over expression of
FLOWERING LOCUS T (FT) was done.
It was found that FT expression led to
very early flowering, with events showing
floral buds within 1–5 months of
transplanting to the glasshouse.
FT overexpression induces precocious flowering and
normal reproductive development in Eucalyptus
Amy L. , et al., 2015

30. Flowering can be
prevented by:
Physical methods
Chemical methods
Genetic engineering

31. Two main approaches have been
employed in the prevention of flowering:
Tissue-specific ablation
Suppression of essential gene(s).

32. The basic idea is to ligate a cytotoxic gene to a gene
promoter that only functions in the floral tissues.
When the gene is turned on at a certain stage of
inflorescence, the gene product kills the target cells,
hence by preventing further inflorescence.
The two cytotoxic genes used are
Diptheretoxin A(DTA)
BARNASE
In Arabidopsis, some transgenic BARNASE
transformants produced inflorescences with flowers
that lacked stamens and pistils, while some
transformants did not produce any inflorescences.
DTA and BARNASE, decreased growth in both
male and female clones of aspen.
Kumar and Fladung, 2005

33. Expression of gene(s) that is
absolutely necessary for inflorescence or
flower development is supressed.
Antisense RNA technique
Transformation of Arabidopis with
an antisense RNA construct has resulted
in complete sterility.
Kumar and Fladung, 2005

34. Methods for floral induction will enable breeders to
more rapidly improve populations.
Demonstrating stability of transgene inheritance and
expression
Rapid identification and breeding of genetically superior
individuals
Prevention will enhance environmental containment of
transgenes
Each species and site will require careful analysis with
regard to timing, mode and duration of application of the
technique.