Agriculture Reference
In-Depth Information
(a)
(b)
R
S
1.5
R
1.0
F
S
0.5
F
L
L
MJJ
Month
ASOND
MJJ
Month
ASOND
Figure 8.10
Cumulative dry matter production of fruiting (
a
) and
defruited (
b
) trees of 'Starkspur Golden Delicious' at Montpellier,
France. Fruiting trees include weight of shed fruits,de-fruited trees
weight of fruitlets removed in May. R,root; S,shoot; F,fruit; L,leaf.
From Heim
et al.
(1979). Reproduced with permission.
dormancy in different parts of the tree structure may also result in changes
in competitive ability. For this reason it is important to look at competition
through the year.
Kandiah (
) found that leaves fed with
CO
in October still contained
% of the total plant extractable activity at leaf fall and the stem above the
upper fed leaves had negligible amounts of the tracer. By December the label
was primarily in the wood of the old stems and, especially, the roots. Forty-eight
per cent of the extractable activity and
% of the activity in the residues at
that time was in the roots.
In the spring following autumn supply of
CO
to the leaves, radioactivity
is concentrated in the first-formed leaves although present in all new leaf and
shoot growth (Quinlan,
c) found that over the period from
leaf fall to spring after leafing-out there is a large reduction in the content of
previously supplied
C in the root system and bark. This stored carbohydrate
is very important as a source of respiratory energy as well as for shoot growth.
Circumstancesthatreducecarbohydrateavailabilityintheautumn,andstored
carbohydrate levels in winter, have a number of adverse effects. Hand defoli-
ation of single-shoot apple nursery trees (whips) at the beginning of October
followed by storage over winter and planting in spring led to low carbohydrate
content, and poor tree survival and growth, compared with controls or trees
defoliated later (Abusrewil and Larsen,
). Hansen (
). Such small trees would have
both low reserves, even in the absence of defoliation, and very high demand
for both root and shoot growth. Early harvesting of fruits, which should enable
