Download FRUITING

FRUITING

 Growth stages
Juvenile phase: The non-flowering period after seed germination.
 Morphological differences
Leaf shape and thickness
Ability to form adventitious roots
 Seedling can not be induced to flower by any means
Transition to the adult phase occurs when the tissue reaches a certain stage
Grafting of mature tissues results in shoots that maintain their flowering
Increasing the growth rate by any means decreases the juvenile period
(transition)
N
High rate of growth
N
Grafting
Extensive pruning
Vigorous rootstock
GA treatments
Horizontals branching
Ringing of branches
Dwarfing rootstocks
Ethaphone treatments
 Flowering
3 major developmental processes occurring during two successive growing
seasons
 Initiation: The time when the meristem is committed to form a flower.
Usually occurs early during active vegetative growth.
There are no visual clues to this development
 Differentiation: Starts the time terminal growth on a tree stops.
Actual flowering structures appear
Before entering winter dormancy, flower buds have developed to
85% of their size
Anthesis: Flower opening and shedding of the pollen
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Time of flower initiation and anthesis of some deciduous fruits
Kind
Beginning of induction
or initiation
Flowers borne on
Peach
Late June-late July
Lateral buds, 1 yr. shoots
Apricot
Early Aug
Next spring
Cherry, sweet
Early July
Lateral buds, 1 yr. Shoots
+ 2 yr. spurs
Lateral buds, 2 yr. spurs
Mid-July
Lateral buds, 2 yr. spurs
Next spring
Apple
Mid-June-mid-July
Terminal buds. 2yr.spurs
Next spring
Pear
Early July– early Aug.
Terminal buds. 2yr.spurs
Next spring
Mid-summer
Next spring
Cherry, sour
Season of anthesis
relative to season of
initiation
Next spring
Next spring
Strawberry
Fall
Compound bur “eye” on
last year’s cane
Terminal bud
Blueberry
Late summer into fall
One year and older wood
Next spring
Raspberry
Late summer
Floricanes
Next spring
Grape
Next spring

 Factors influencing flower bud formation




The vegetative needs to be at a certain stage. A critical node number is
required I.e., 20 nodes for Cox’s Orange Pippin and 16 nodes for Golden
Delicious
Hormonal balance
Change in the distribution of nutrients inside the apical meristem
Development of flower buds does not start unifromly throughout the tree. In
apple the terminal bud of a spur begin their transformation 4-6 weeks earlier
than lateral buds
 Light
In apples, areas receiving < 30% of sunlight , no spurs form. This is due to the
limited movement of CHO within the tree

 Spur leaf area
In pear, return bloom increased with increased spur leaf area to about 90 cm2 (56 leaves)

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
 Tree vigor
Vigorous growth decreased flower bud initiation
Pruning increases vigor and decreases flower bud initiation
In peaches bud development occurs in shoots with less than 200mm per
internode
Trees with low vigor are unable to initiate flower buds due to lack of CHO
 Hormones
 Gibberellins
type
seeds
apical meristem and young leaves
some compounds counteract GA such as ethephon
 Auxin
 Ethylene
 Cytokinins
 General conclusion: Floral initiation occurs in fruit trees when GA in the bud
is below a critical inhibitory level, and the balance of other hormones-auxin,
cytokinins, ethylene – is favorable for initiation during the normal tine of
initiation for that species

 Crop load

 Practices affecting initiation (see factors affecting juvenility…)
Flower development
Flowers are mostly developed by the time they enter winter dormancy
Very slow development occurs during winter
Rapid development occurs in the spring
Factors affecting flower development
 Age of wood
 Position on tree
 Temperature
 CHO availability
 Water availability
 Growth regulators
 Winter chilling
 N fertilization
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FRUIT TYPE OF
BUDS
FLOWER
BUDS
INFLORESC FLOWE TIME OF
ENCE
R
FLOWER
NUMBE INITIATION
R
CHARC. CHARC.
1ST
2SN YEAR
YEAR
WOOD
WOOD
Where Will initiate Where
buds are flower buds fruit is
attached for next
found
season
Apple
Vegetative Terminally
and mixed epygenous
Determinate 5
Early
summer
Pear
Vegetative Terminally
and mixed epygenous
Indeterminate 7-8
60 days past Similar to Similar to
full bloom
apple
apple
CHARC WOOD
3RD
PRODUCTIVITY
YEAR
WOOD
Youngest wood
most productive
Similar Similar to apple
to apple
Peach Unmixed
Lateral
Solitary
hypogenous
1
Mid-summer Where
fruit is
located
Inferior
flower buds
Cherry Unmixed
clusters
Lateral
Cluster
hypogenous
2-4
July, after
crop is
harvested
Sweet
Cherrybest spurs
Sour
cherry-
Long productivity
10 -15 years in
sweet cherry
Plum
Lateral
1-3 flowers/
hypogenous bud
1-3
Mid to late
summer
Most
vigorous
spurs Fruit
production
Similar to apple,
spurs older than 4
years may die
Unmixed
Sweet
Cherryspurs
Sour
cherrylong
shoots
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Flower Phenology
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 Pollination and fruit set
Parthenocarpic: Requiring no pollination for fruit development, seedless
Self-fruitful: Capable of setting a commercial crop following self-pollination
Self-unfruitful: Requiring cross-pollination
Polyploid: has more than the dipolid number of chromosomes. Pollen is not
viable. Can not be used as a pollinator, and needs to be cross-pollinated
Incompatible: Having viable pollen, but incapable of setting fruit when crosspollinated with certain cultivars. i.e., Cortland X Early McIntosh
Is pollination required?
Factors affecting pollination
 Compatibility
 Pollen viability
 Effective pollination period (EPP)
 Pollinizer placement
 Pollinators
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Effective pollination period for apples and pears
Tree
Apples
Pears
Peaches
Sweet
Cherries
Sour
Cherries
Grapes
Cross pollination
required
Yes
Yes
No
Most, yes
Most, no
Most, no
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Pollination vs. fertilization (see fig. 1 in chpt 9 Fruit set. In Tree Fruit
Physiology)
Tree factors affecting fruit set other than pollination
 Cultivars that are self-fruitful tend to set more heavily than those that are selfunfruitful.
 As bloom density increases the percentage of fruit set decreases due to
competition among flowers. The carbohydrate rations and growth regulator
substances manufactured by the plant usually only satisfy less than 20% of
the growing fruitlets. Therefore, most of the fruiting clusters are shortchanged
and drop their fruitlets.
 In an apple tree with heavy bloom, only 10% percent of the flowers will
eventually develop into fruits. More set, 15 to 20%, may be needed in trees
with sparse bloom.
 Young trees, especially on vigorous rootstocks, often set poorly.
 Trees on semi-dwarf and dwarfing rootstocks tend to set more fruit than
seedling rootstock.
 The quality of the fruit cluster buds. As a rule, the smaller and poorer quality
cluster buds show a greater fruit drop or produce smaller apples. The
following are common characteristics associated with good and poor quality
fruit buds.
Cluster fruit bud characteristics:
Week cluster bud
Vigorous cluster bud
Fewer, smaller leaves
5-8 ovules
10-18 stamens
2-4 pistils
2-4 flowers
Found in older (>5 yr.) wood
Weaker trees
Located in interior canopy
Too much vegetative vigor
More, larger leaves
10 ovules
20 stamens
5 pistils
6-7 flowers
Found in younger (<5 yr.) wood
Well-nourished trees
Located in exterior of canopy
Average vigor
Cultural factors affecting fruit set
 Shading has a marked effect on fruit set, especially as the light levels drop to
less than 40% of full sun. Shaded fruitlets have less cell division than
exposed fruitlets.
 The 35 days post-bloom period is important to production from two respects:
 First, fruit cell division, which occurs during this period, affects ultimate
fruit size and condition, and
 Secondly, spurs not producing apples in ‘98 are establishing fruit buds for
‘99. Ideally, the more spurs that come in contact with light, the better off
each crop will become in terms of potential profitability. Therefore,
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summer pruning (thinning out or cutting back) of current shoots or younger
branches to provide better light distribution is a benefit where crop loads
are justified.
 Nutrition is a crucial factor in fruit set. Deficiencies in nitrogen, boron, zinc,
and manganese will reduce fruit set.
 Ringing (removal of a section of bark around the trunk or scoring (cutting the
bark) can improve fruit set. Ringing is done 7 days after full bloom.
 Branch bending can increase flower bud formation and fruit set. Bending can
be done in the spring, prior to bloom or in August when the majority of the
shoots have formed terminal buds, and the cambium is still active.
 Apple Thinning

It has been estimated that 90% of apple growers in the United States use
some form of chemical thinning to improve fruit size and to promote annual
cropping.
 No single thinning program applies to all cultivars.
 The thinning response varies depending on climate and cultural conditions.
The past history of the orchard, the grower's experiences with particular blocks,
the cultivar, and the weather conditions should be used to determine the best
time of application and the rates of the individual or combinations of thinners.
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Table 3. Tree and weather conditions affecting thinning with chemicals
(Good Fruit Grower, April 1, 1998)
Easy to thin when:
1. Heavy or "snowball "bloom or a
previous heavy crop
2. Nitrogen is low
3. Moisture is inadequate
4. Root system is weak due to injury
or disease
5. Fruit spurs are low in vigor on the
shaded inside branches
6. Trees are self-pollinated or poorlypollinated
7. Fruit-set appears heavy on easilythinned cultivars such as Delicious
8. Fruit sets in clusters rather than
singles
9. The cultivars tend to have a heavy
"June drop"
10. Bloom period is short and
pollination is inadequate
11. High temperature is accompanied
by high humidity before or after
spraying
12. Blossoms and young leaves are
injured by frost before the spray
application
13. Foliage is condition for increased
chemical absorption by prolonged
cloudy periods before spraying
14. Prolong cloudy periods reduce
photosynthesis before of after the
absorption of chemicals
15. When stress and endogenous
ethylene production are high
Difficult to thin when:
1. Insects are active in orchards of
cross-pollinated cultivars
2. Trees are in good vigor with 12 -18
inches terminal growth and there are
no mineral deficiencies
3. Precocious trees come into fruiting
with good vigor and mature bearing
habit
4. Fruits are developing on spurs in welllighted areas of trees (tops and outer
canopy)
5. Biennial bearing trees are in "on year"
6. Trees have horizontal or spreading
fruiting branches
7. Fruit set is in singles rather than
clusters
8. Cultivars are heavy-setting spur types
or Golden Delicious or Fuji
9. Ideal fruit growth conditions occur
before and after thinning period
10. Low humidity causes rapid drying of
the trees and decrease absorption
11. Mild temperatures occur after bloom
without any tree stress
12. Bloom is light, and high leaf-to-fruit
ratio occurs
13. Limbs and/or spurs are slightly girdled
from winter injury
14. Stress and endogenous ethylene
production are low
15. Small fruited varieties
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Table 4. Thinning Windows (Apple Thinning Guide)
Thinning
Bloom
Petal Fall Early Fruit
Late Fruit Set Closing
Window
Set
DAFB
5 to 10
11 to 15
16 to 20
20+
Fruit Size(mm)
PF to 8
8 to 12
16 to 20
20+
Stage (mm)
Full
Petal 6 8 10
15
20
25
Bloom Fall
General
Thinning
Fair
Best
Good
Good
OK
Success
Past Thinning
Traditional
Rescue
Window
thinning
Table 5. SPECIFIC THINNING RECOMMENDATIONS.
Cultivar
Stage of fruit development
Petal fall to 3 mm
McIntosh
Sevin
Cortland
Sevin
Delicious (Promalin at
Sevin
bloom)
Empire
Sevin
Macoun
Macoun (alternative)
Sevin+5-7.5NAA
Sevin
Golden Delicoius
Sevin
7 to 12 mm
Sevin+2.5-7.5NAA or
Sevin+50-75Accel
Sevin
15+ mm
Sevin
Sevin
Sevin (+75Accel if needed) Sevin
Sevin+7.5-10NAA or
Sevin+50-75Accel
Sevin+5-7.5NAA
Sevin+75-100Accel
Sevin+10-15NAA or
Sevin+75-100 Accel
Sevin
Sevin
Sevin
Sevin
Source – Sink interaction
Leaves and other green tissues are the original sources of assimilates
Most assimilates are exported (translocated ) to sinks for growth, maintenance,
and storage
During vegetative growth, roots, stems, and young leaves are competitive sinks
Sink demands change during the life cycle of the plant
Leaves become autotrophic when 1/3 to 1/2 of their final area is developed
After flowering, the reproductive sink becomes very strong, and limits the
assimilate partitioned to vegetative sink.
Fruits are very strong sinks
The presence of fruit effectively limits the growth of the tree in apples
200cm2 of leaf area is needed to grow a 100g apple. An additional 75 cm2 are
needed for each increment of 25g
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√ Roots
Regulate the growth and performance of fruit trees
Interact with the soil
√ Water uptake
√ Assimilation of nutrients
√ Storage organs for carbohydrates
Genetic control over the arial portion
√ Size
√ Date of bloom
√ Amount of bloom
√ Precocity
√ Time of harvest
√ Winter hardiness
Resistance
√ Vertebrates
√ Diseases
√ Insects
Structure for support
√ Anchorage
REL. ROOT GROWTH RATE
√ Root growth
100
90
80
70
60
50
40
30
20
10
0
0
5
10 15 20 25 30 35 40 45 50
TEMPERATURE (C)
√ Root distribution
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Distribution varies according to
 the soil profile
 Oxygen concentration and moisture
Majority of roots in the top 25-50 cm
√ Water uptake
Water use is directly related to tree productivity even under conditions when the
trees are not visibly stressed
Dry weight increases in apples and peaches is proportional to the transpiration
General order for water requirements:
Quince>pear>plum>peach>apple>cherry>sour cherry>apricot
√ Apoplastic
√ Symplastic
Osmosis
The water status of a plant is measured by its water potential
 Osmotic potential arising from the dissolved solutes in the water
 Turgor potential arising from balance between internal and external pressures
 Matric potential arising from the capillary forces at thee water-air interface
 Gravitational potential
Drought tolerant rootstocks usually have wide spreading roots which tend to grow
downward
Drought prone rootstocks are relatively confined and have many feeder roots.
They are very efficient at extracting water from their confined area
√ Nutrient Uptake
√ Passive
√ Active
√ Growth patterns
Root growth
See figures 1 and 2 in Chapter 5 Coordination of root and shoot growth in your
textbook, Tree Fruit Physiology
 2 periods
 Early spring
 Late summer
Shoot growth
 Begins at bud break till mid-summer
 Extension may stop, but shoot, branch and trunk diameter continue to
increase
Spur growth
 Usually 2 to 6 weeks after bud break
Spur leaves
 First to emerge, but only maintained for 60 to 90 days
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Flower bud formation
 Initiation early to midsummer
Relative rootstock sizes
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