Agriculture Reference
In-Depth Information
Table
.
Number of leaves produced (nodes) and length of shoot (cm) made during a
-week period at the temperature shown (means of six trees)
Pruning treatments, shoots per tree
Temp of
CE rooms
lower
upper
lower
middle
upper
Mean
◦
C
Leaves
Shoot
.
◦
C
Leaves
Shoot
◦
C
Leaves
Shoot
After Abbott (). Reproduced with permission.
of an apple tree can behave as a storage organ for carbohydrates. Carbo-
hydrate reserves are primarily used up in respiration, supplying energy for
growth, rather than in provision of structural material. Most of the nitrogen
for early growth comes from the bark of branches and shoots near the expand-
ing buds (Mason and Whitfield,
; Tromp and Ovaa,
; Titus and Kang,
).
Effects of temperature
Abbott (
), using controlled environment rooms, showed that the rate of
extension growth of shoots arising following decapitation of potted 'Cox' trees
increased progressively over the range of
◦
C(Table
). This was so
even when only a single shoot was allowed to grow as a replacement leader.
These results provide experimental support for the field observations of Barlow
(
-
.
a) and Johnson and Lakso (
), who showed shoot growth to be a func-
tion of temperature. Tromp (
a) found a relatively small effect of increasing
◦
C on the terminal shoot growth of newly
budded trees but a large effect on total lateral shoot growth. He also (Tromp,
◦
Cto
soil temperature from
b) showed greatly reduced lateral shoot numbers and consequently total
shoot growth when root temperatures were at
◦
C compared with
◦
Cor
higher.
Effects of light
Artificial shading of whole trees results in a reduction in total shoot growth
(Priestley,
a). This effect is primarily through
a reduction in the number of shoots that grow and, to a lesser extent, to a
; Jackson and Palmer,
