Flower Induction

1
Flower Induction Hormonal and Substrate Control
Karthik-Joseph John Horticultural Sciences
Department University of Florida
2
Monselise and Halevy. 1964. Chemical Inhibition
and Promotion of Citrus Flower Bud Induction.
3
Introduction

• Gibberellic acid inhibits flower formation in
  apples, pears, peaches and many other plants
• First paper to study the effect of GA on citrus
  flower induction
• Study the GA effect on citrus and to better
  understand the timing of bud induction
• Use of anti-GA or other growth regulators to
  induce flowering in lemons as an alternative to
  withholding irrigation

4
Materials and Methods

• Experiment 1
• Shamouti oranges 1 branch/tree on the southern
  part of each tree
• Treatments 200 ppm of GA sprays for 3, 4, 5 or
  6 times at 2-week intervals from November 3
• 4 replications per treatment
• Flowers were counted on the branches on April 5
• Sprouting vegetative buds were recorded on
  January 1 and February 12

5
Materials and Methods

• Experiment 2
• Eureka lemons 2 branches/tree on the
  south-eastern side
• Treatments 2 sprays of 0.2 Cycocel, 0.2 B
  Nine, 50ppm BTOA or 500ppm GA
• Flower buds, flowers and fruitlets less than 2
  cm in diameter were counted on Nov. 4
• Withhold irrigation for 2 months starting
  mid-august???

6
Results and Discussion

• Experiment 1
• GA spray inhibited flower formation
• GA treatment delayed flower differentiation

No statistics
7
Results and Discussion

• Very few flowers differentiate if GA effect
  lasts during the main induction period

No statistics
8
Results and Discussion

• Experiment 2
• No flowering in control and GA treated trees
• BTOA induced maximum flowering

No statistics
9
Results and Discussion

• Effect of BTOA on citrus leaves
• Rolling of leaf margins in leaves of the new
  growth produced under the influence of the
  chemical
• Formation of flower clusters at the apex of the
  young branches

Leaf symptoms found with GA are well known
10
Overview

• Abstract is missing
• Experimental design is not mentioned
• Only southern part of the tree is used so
  results may not represent the overall effect
• What is the basis for selecting the conc. of GA?
• No statistical analysis
• In experiment 1, data for measurements on Jan 1
  is missing
• No details on the leaf symptoms due to GA
• Typing error?

11
Discussion
12
Guardiola et al. 1977. Gibberellic acid and
flower bud development in sweet orange.
13
Introduction

• The inhibitory effect of GA is used to control
  alternate bearing
• The mechanism of the inhibitory action is
  unknown
• Earlier hypothesis
• GA interferes with flower induction
• GA may reverse flower bud to a vegetative apex
  through an indirect mechanism
• A different mechanism of action of GA on
  flowering is observed

14
Materials and Methods

• Sweet orange trees Navelate and Washington
  navel
• No other details were given in materials and
  methods

15
Results and Discussion

• GA sprays during winter greatly reduced
  flowering
• The effect depends on the concentration and time
  of application

Absolute values were not presented
16
Results and Discussion

• There is decrease in the leafless type of
  inflorescences with a parallel increase in the
  vegetative shoots

17
Results and Discussion

• Number of leaves per shoot increased but there
  was no change in the number of flowers

18
Results and Discussion

• Inhibition in flowering is mainly due to
  decrease in number of shoots of RF and S types

19
Results and Discussion

• The buds in the more apical nodes started growth
  earlier and in a greater number than in the more
  basal
• GA did not affect the proportion of shoots which
  abscise during early phases of development

No statistics shown in figure
20
Overview

• The main effect of GA lies in the inhibition of
  bud development
• Insufficient information about the materials and
  methods
• Statistical analysis is not show for the figure
• Results and interpretation were difficult to
  understand

21
Discussion
22
Davenport. 1983. Daminozide and Gibberellin
Effects on Floral Induction of Citrus latifolia.
23
Introduction

• Tahiti limes grown in southern Florida are ever
  bearing
• Heavy flushes of flowers Jan., Feb. and March
• Fewer flowers several times throughout the
  year
• Majority of production summer months
• It is desirable to induce heavy flowering in any
  flush to increase off season crop

24
Materials and Methods

• 18 year old Tahiti lime trees
• 3 treatments 0.1mM GA, 2500 ppm daminozide and
  distilled water control
• 4 replications per treatment
• First experiment
• Treatments applied in mid-August at the onset of
  summer flush
• 3 sprays in one week period
• Daminozide concentration 500 ppm
• Total number of new shoot and shoot type were
  observed in mid-September

25
Materials and Methods

• Second experiment
• First spray was done in mid-December, prior to
  spring flush
• 2 weekly sprays of 500 ppm daminozide followed
  by 4 weekly sprays of 1000 ppm
• These were followed by 2500 ppm daminozide prior
  to and during the spring flush
• GA and control were applied at all times

26
Results and Discussion

• The flush was vegetative which is typical for
  that time of year
• No tendency to flower in daminozide treatment
• GA increased the number of shoots produced
• The morphology of vegetative shoots in the GA
  treatment was comparable to control and
  daminozide treatment

27
Results and Discussion

• GA treatment shifted shoot type from
  predominantly flowering to mainly vegetative
• Daminozide inhibited flowering

28
Overview

• Materials and methods were not organized
  together
• Details of experimental design and statistical
  analysis were not mentioned
• The data from the west side of the trees are not
  reliable the western side was crowded due to
  closely placed adjacent rows and so there was
  shading and also the sprays were unable to cover
  completely on this side

29
Discussion
30
Garcia-Luis et al. 1986. Inhibition of flowering
in vivo by existing fruits and applied growth
regulators in Citrus unshiu
31
Introduction

• Flowering in citrus is inversely related to the
  previous crop
• This could be due to an interference in the
  build-up of reserves and hormonal imbalance
• This study investigates the time course of
  flowering inhibition by the fruit
• This effect is compared to the application of GA
• Also studied the effect of kinetin, ABA and 2,4-D

32
Materials and Methods

• 10 year old Owari Satsuma mandarin
• Randomized Block Design with single whole tree
  replicates
• 5 µL drop of 200 ppm solution of growth
  regulator was placed directly on the bud
• Growth regulators GA, ABA, kinetin and 2,4-D
  were used
• 10 most apical buds from each twig from previous
  summer were selected
• 20 twigs were selected for each compound
• Application from middle Dec. to middle Jan.
• Whole tree spray was also done using the
  chemicals

33
Results and discussion

• Only GA reduced the number of sprouted nodes

34
Results and discussion

• Similar response was obtained when GA and
  kinetin were applied to entire tree instead of
  locally to the buds

35
Results and discussion

• Influence of time of GA application on flowering

No statistics
36
Results and discussion

• Influence of time of GA application on spouting

37
Overview

• Most data support the work done earlier
• The inhibitory effect of GA and kinetin on bud
  sprouting contrasts with the promotive effect
  found when applied to non-flowering seedlings and
  young trees
• Good experimental design
• Statistics is done but no statistics is shown
  for figure 3

38
Discussion
39
Koshita et al. 1999. Involvement of endogenous
plant hormones (IAA, ABA, GAs) in leaves and
flower bud formation of satsuma mandarin (Citrus
unshiu Marc.)
40
Introduction

• This paper investigates the effect of the levels
  of endogenous plant hormones in relation to
  flowering
• The relation to other plant hormones was not
  simultaneously investigated
• The aim of this study is to clarify the
  relationship between flower bud formation and
  plant hormones (IAA, ABA, GA1/3, GA4/7) contents

41
Materials and Methods

• 25 year old satsuma mandarin
• 8 lateral branches consisting of only vegetative
  shoots were chosen in each tree
• 4 of them are ringed
• 60 fruit bearing shoots are selected in each tree

42
Results and Discussion
43
Results and Discussion

• IAA and ABA contents in the leaves

44
Results and Discussion

• GA content in the leaves

45
Overview

• In October, higher endogenous GA levels may be
  one of the reasons for vegetative growth in the
  following spring
• In Dec. and Feb. only slight difference was
  observed in GA content between bearing and
  vegetative shoots this supports the work of
  others
• Increase of leafless inflorescence and
  enhancement of ABA in Dec. and Feb. and of IAA in
  Dec. suggests that endogenous ABA and IAA may
  affect flower bud development

46
Discussion
47
Jona et al. 1971. Further Studies on the Effect
of Nucleic Acids on Shoot and Flower Formation in
Citrus Trees.
48
Introduction

• FUdR is a specific DNA synthesis inhibitor which
  promotes flowering in citrus
• This controls flower formation at the stage of
  cell division in the growing apex
• This paper deals with the effects of this
  chemical on flower and shoot formation
• The role of cell division in flower formation
  was studied by applying FUdR and TdR during the
  induction and differentiation period

49
Materials and Methods

• 36 year old Shamouti orange trees
• TdR and FUdR were applied either alone or in
  combinations at 10-3 M
• Each chemical solution was brushed on leaves,
  stem and buds of 10 spring branches beginning
  Oct. 17
• Application was repeated at 10 day intervals
• There were 2 series of treatments. In one the
  last treatment was applied on Dec. 17 and in
  another on Jan. 18

50
Results and Discussion

• Effects on the number of sprouting buds during
  the spring flush

No statistics
51
Results and Discussion

• Effects on the number of lateral shoots
  developing during the spring flush

No statistics
52
Results and Discussion

• Effects on the number of lateral shoots per
  sprouting internode during the spring flush

No statistics
53
Results and Discussion

• Effects on the type of new lateral shoots
• No significant difference when FUdR or TdR are
  applied separately

No statistics
54
Results and Discussion

• Effects on flower formation

55
Results and Discussion

• Effects on mitotic activity in the apex during
  floral induction and differentiation

56
Overview

• FUdR is a DNA synthesis inhibitor and it can
  affect RNA synthesis when it is converted to
  5-Fluorouracil
• TdR may counteract the effect of FUdR on DNA but
  not on RNA
• So, the inhibition of RNA synthesis is crucial
  for the promotion and bud opening
• Thus, FUdR TdR promotes flower formation by
  interfering with RNA metabolism
• No details on experimental design were given
• They have mentioned the use of std. errors and
  multiple range test, but they were not shown in
  the graphs

57
Discussion
58
Goldschmidt et al. 1985. A Role for Carbohydrate
Levels in the Control of Flowering in Citrus.
59
Introduction

• Carbohydrate levels have been suggested as a
  limiting factor for flower formation in citrus
• In this study, they examined several lines of
  evidence for the role of carbohydrates and their
  possible interaction with other factors in the
  control of flowering

60
Materials and Methods

• Mature, shy bearing Shamouti orange trees
• Girdling was done in late October
• Half of control and half of girdled trees were
  sprayed with 72 µM GA in Nov. and Dec.
• 3 year old potted Minneola tangelo were used in
  another experiment in which plants are subjected
  to various day/night temperatures

61
Results and Discussion

• Effects of girdling on starch and flowering
• There is correlation between elevated
  carbohydrate levels and flowering

62
Results and Discussion

• Starch contents in leaves and twigs as affected
  by GA and girdling

63
Results and Discussion

• Effect of GA and girdling on shoot type
• GA counteracted the girdling effect

64
Results and Discussion

• Quantitative effects of cool temperatures on the
  promotion of flowering
• Starch levels did not correlate well with
  flowering
• Intensity of flowering was in accordance with
  the exposure to cold temperatures

65
Overview

• Carbohydrate levels play a role in flower
  induction but it is not always the limiting
  factor
• More details could have been added in the
  Materials and Methods section e.g.. Light
  intensities used for the experiments
• Experimental design and statistical methods were
  not explained in the Materials and Methods. But
  statistics is well explained for each table

66
Discussion
67
Monerri and Guardiola. 2001. Peroxidase activity
and isoenzyme profile in buds and leaves in
relation to flowering in satsuma mandarin.
68
Introduction

• Changes in peroxidase activity and isoenzyme
  profiles have been described during flower
  induction in other species
• The aim of this work is to determine if the
  changes in peroxidase activity and isoenzyme
  profiles can be related to the developmental
  states of the buds
• They have compared the seasonal changes in
  peroxidase activity and isoenzyme pattern in
  young flowering and in adult flowering trees

69
Materials and Methods

• 1 year old and 30 year old trees of satsuma
  mandarin were used to study seasonal changes
• 3 year old potted trees were used to study the
  changes during low temperature flower induction
• To study the effect of girdling, adult trees
  were girdled by mid-September

70
Results and discussion

• Fractionation of enzyme activity

71
Results and discussion

• Isoenzyme patterns of soluble and ionically
  bound cell wall peroxidases

72
Results and discussion

• Changes in fresh weight of buds and leaves

73
Results and discussion

• Changes in peroxidase activity in leaves
• In adult trees, high peroxidase activities were
  mostly established by Sep. before the buds
  acquired competence to flower

74
Results and discussion

• Isoenzyme patterns in leaves

75
Results and discussion

• Changes in peroxidase activity in buds

76
Results and discussion

• Isoenzyme patterns in buds

77
Results and discussion

• Effect of girdling on peroxidase activity

78
Results and discussion

• Effect of inductive low temperature conditions

79
Overview

• Higher peroxidase activities in the leaves from
  flowering trees compared to non-flowering trees
  could not be related to the flowering process
• Consistent differences in peroxidase activity
  related to flowering was not found in the buds
• Girdling had no effect on peroxidase activity
• So, the enzyme fractions and the isoenzyme
  patterns are not useful markers for developmental
  flowering stages of the buds
• Only one parameter was considered in this paper

80
Discussion