Agriculture Reference
In-Depth Information
Table
.
Effects of rootstock and deblossoming on the vegetative growth and fruit yield of
'Laxton's Superb' at
years
Accumulated weight (kg/tree)
Deblossomed
Cropping
Total
Rootstock
Leaf Wood Root Total Leaf Wood Root vegetative Fruit
Light pruned
'M.'
.
.
.
'M. '
.
.
.
Hard pruned
'M.'
.
.
.
.
'M. '
.
.
.
.
Data from Barlow and Smith (). Reproduced with permission.
and a lower proportion of young leaves with high photosynthetic rates late in
the season. Measured effects of rootstock on photosynthesis per unit leaf area
have been contradictory and usually small (Barden,
).
The results may be partly confounded by effects of crop load on photosynthe-
sis and the comparisons of similar leaves may not give a relevant picture of
total photosynthesis by leaf populations which differ in age structure. It does,
however, seem that particularly in trees which have already begun to differ
in size, the main effect of rootstock on photosynthetic potential is through its
effect on leaf area.
; Wunsche
et al.
,
.
Dwarfing rootstocks induce precocious and heavy fruiting at the expense of vegeta-
tive growth.
Rootstocks have a major effect on the partitioning of assimilates.
'M.
' and its derivatives are precocious in flowering and induce early, heavy
cropping in any scion cultivar grafted on them. This is not a response to their
dwarfing effect but is shown before the latter becomes marked. At maturity
trees on dwarfing rootstocks in general show a much higher ratio of fruit yield
to vegetative growth increment than do trees on the more vigorous rootstocks.
Heavy fruiting not only checks growth in the year of cropping, especially root
growth, but also growth in the following year ( Jackson,
). This indirect
effect on scion vigour via effects on fruiting is responsible for an appreciable
component of apple rootstock effects on vigour. Apple trees of 'Laxton's Su-
perb' on 'M.
' which had been deblossomed from planting produced
%
as much accumulated dry matter (growth) over
years as corresponding
trees on 'M.
'. When each had been allowed to crop, vegetative growth on
'M.
' was only
%ofthaton'M.
'(Table
.
). The trees on 'M.
' that had
been allowed to crop made only
% of the growth of those that had been
deblossomed.
