temperate fruit trees

Question 1

Chilling requirement & rest period

Answer 1

The amount of cold needed by a plant to resume
normal spring growth following the winter period is
“chilling requirement.”

Plant species/horticultural varieties vary widely in their winter cold requirement.

During the fall and winter, deciduous fruit plants enter a dormant period which referred to as the plants’ “rest period.”

Question 2

What happens during winter chilling?

Answer 2

Plants enter rest period in autumn
temp drops to 10°C
leaf fall occurs
visible growth ceases

As growth regulating inhibitors increase ,growth regulating promoters decrease, plants begin dormant period

As chilling requirement is satisfied, the level of promoters begins increasing while the level of inhibitor decreases

Higher levels of promoters in the buds allow normal resumption of growth and flowering in the spring.

Question 3

Dormancy and rest period temperature

Answer 3

2oC to 13oC – chilling effect

Most efficient chilling = 7oC

7oC-16oC contributes to chilling

Question 4

Tropical & sub-tropical, the limiting factor is the …………………..
Not receiving chilling periods will suffer a physiological condition
how to over comd insufficient chilling

Answer 4

..chilling factor
delayed foliation”-abnormally long flowering periods and leaf production will be sporadic.
Sufficient chilling, 2 weeks flowering and form leaves

Insufficient chilling overcome with cultivar selection, careful site selection and the use of rest breaking treatments

Question 5

Chilling requirement for fruits type

Answer 5

Apple, standard,Pear European hybrids-
800-1100 
Cherry-1000
Muscadine grape-200-600
Plum, Japanese-400-750
Peach and nectarine-400-1050
Asian pear-600-900
pear european-400-900

Question 6

Each type/variety of plant has a particular “heat unit” or……………….requirement to reach a given level of bud, flower, and fruit development
Once CR is satisfied, the buds slowly break dormancy as temp climb above ……….

Answer 6

growing degree hour

4.4°C.

Question 7

GDHs begin accumulating as air temp………. rises to higher
If the air temperature does not rise above 40°F (4.4°C), no ………………

Warm day in spring results ………..GDHs accumulating in 24 hours

Answer 7

5°C &
GDHs accumulate
Temperatures above 25°C - no additional heat benefit derived
650 -700
The GDHs for each hour are totaled over time & can be used to predict the stage of development of the plant.
eg.Peaches require 10,000 to 13,000 GDHs to reach 50 percent bloom stage after rest is satisfied

Question 8

Combination of CR & GDHs
ideal fruit type - possesses a CR ………….for the area & high to very high ………….. requirement. This ensures later flowering & more consistent cropping

Answer 8

Combination of CHR & GDHs determine flowers early, midseason or late in late winter/spring
satisfactory
growing hour degree
However, many varieties being grown do not have ideal chilling/GDH requirement combination