Articles
The position of one-year-old shoots of the apple tree can affect the chilling requirement of their tip buds
Article number
1457_73
Pages
581 – 592
Language
English
Abstract
Chilling temperatures mainly overcome endodormancy of buds on temperate fruit trees during autumn and winter.
Cultural practices and rootstocks can either increase or reduce the effects of chilling temperatures.
In tropical and subtropical zones, bending shoots of temperate fruit trees has been shown to enhance bud break and crop production.
Apical buds of one-year-old shoots of these species may have different chilling requirements and growth responses depending on their position (horizontal or vertical) on the branches.
On the branches of some apple trees, horizontal and vertical one-year-old shoots were collected in separate bunches every week from December to February for six years.
During the winter season, one-year-old twigs were kept with their bases in water and in a growth chamber for 20 days at 21°C. Apical buds that grew were counted and evaluated as a percentage of the total and bud development stage (BDS). Temperatures during the winter were recorded, and both the chilling units (Richardson) and the Dynamic Model chilling portion formulas were tested.
The onset of bud break and the end of rest in one-year-old shoots were assessed using the chilling unit (CU) to chilling portion (CP) ratio and the aforementioned indexes, along with two parameters (% bud break or burst and bud development stage, BDS). Results indicated that the cultivars can be separated into three groups: one in which the horizontal shoots are highly dominant in reaching bud burst, another in which the vertical shoots are highly important in reaching bud burst, and finally a group in which both kinds of shoots reach bud burst with similar values.
The behavior of the tested horizontal and vertical shoots in relation to overcoming bud endo-dormancy is specific for each cultivar studied, and this should be taken into consideration for: 1) the evaluation of the chilling requirement of the cultivars; 2) the application of some cultural practices, particularly pruning and training forms in apple trees grown in warm winter zones.
Cultural practices and rootstocks can either increase or reduce the effects of chilling temperatures.
In tropical and subtropical zones, bending shoots of temperate fruit trees has been shown to enhance bud break and crop production.
Apical buds of one-year-old shoots of these species may have different chilling requirements and growth responses depending on their position (horizontal or vertical) on the branches.
On the branches of some apple trees, horizontal and vertical one-year-old shoots were collected in separate bunches every week from December to February for six years.
During the winter season, one-year-old twigs were kept with their bases in water and in a growth chamber for 20 days at 21°C. Apical buds that grew were counted and evaluated as a percentage of the total and bud development stage (BDS). Temperatures during the winter were recorded, and both the chilling units (Richardson) and the Dynamic Model chilling portion formulas were tested.
The onset of bud break and the end of rest in one-year-old shoots were assessed using the chilling unit (CU) to chilling portion (CP) ratio and the aforementioned indexes, along with two parameters (% bud break or burst and bud development stage, BDS). Results indicated that the cultivars can be separated into three groups: one in which the horizontal shoots are highly dominant in reaching bud burst, another in which the vertical shoots are highly important in reaching bud burst, and finally a group in which both kinds of shoots reach bud burst with similar values.
The behavior of the tested horizontal and vertical shoots in relation to overcoming bud endo-dormancy is specific for each cultivar studied, and this should be taken into consideration for: 1) the evaluation of the chilling requirement of the cultivars; 2) the application of some cultural practices, particularly pruning and training forms in apple trees grown in warm winter zones.
Publication
Authors
G.A. Finetto
Keywords
meristem, rest, blossom, assessment, chilling unit, chilling portion, bud break
Online Articles (96)