although this has been largely restricted to specific control of an aspect of fruit development,
e.g., the use of GAto control russet or the use of BA as a fruit thinner.

4 + 7

Although we have seen a major development of different orchard systems over the last 40 years,
there have been several common themes to these systems.First, there has been a major emphasis
on precocity, partly in response to the need for a more rapid turnover of cultivars. Precocity has
been enhanced by planting at higher tree densities on more dwarfing rootstocks, the higher tree
densities to increase light interception early in the life of the orchard and the dwarfing rootstock
to increase the partitioning of dry matter into fruit.On a mature orchard of Golden Delicious on
M.9 in East Malling, up to 65% of the annual dry matter could be consistently partitioned into
the fruit.If there is a continual demand for large sized apples it is difficult to see this percentage
rising much higher, as some dry matter must be partitioned into leaves to ensure adequate
photosynthesis and some into the structure of the tree and reserves to maintain the perennial
habit of the tree.

The second major emphasis in modern systems has been upon the production of large, high
quality apples.This can be achieved only by ensuring good light penetration into the canopy.
Control of vegetative growth is critical here.Vegetative growth has been reduced by the use of
dwarfing rootstocks, branch bending, reduced pruning and the greater understanding of the effect
of apical dominance.The Lincoln canopy was a very innovative design by an engineer to ensure
that the fruit had a short distance to travel from the planar canopy to the catching system.
Unfortunately vegetative vigor was excessive from the horizontal branches, as there was no
control by apical dominance.Consequently, fruit color of red apples could be maintained only
with difficulty by excessive summer pruning.

ECONOMICS
The apple tree canopy has shown itself to be very adaptable to manipulation; it responds
reasonably predictably to pruning and branch manipulation; it generally bears ample flowers
throughout the tree on all ages of wood from 1-year-old wood to older spurs; it shows good
variation between scion cultivars and can be drastically altered by the wide range of available
rootstocks.Consequently, there are numerous ways of arranging an apple tree canopy in space
and many of these systems have their vigorous human supporters.The bottom line as always is,
does the system make money?It is easy for the scientist to either forget the economic aspect or
make crude, grossly misleading financial calculations.Financial returns are dependent on the
investment and maintenance costs and the value of the harvested crop.Investment costs can vary
quite widely from grower to grower depending on the individual costs of trees and support
systems.Consequently, the suitability of any system to a particular grower will depend upon the
specific individual cost and the make-up of the rest of the enterprise.It also depends upon the
capability of the grower to manage the system.Intensive systems tend to demand intensive
management, as there is inherently more control being exercised over the tree.If the grower fails
to appreciate this management requirement, the system may not perform as well as anticipated
and not provide the expected return on investment.

CONCLUSIONS
Total dry matter production and yield of fruit of apple both have been linearly related to light
interception.The cultivated apple canopy has shown itself to be very adaptable to canopy
manipulation by the use of rootstocks, tree training and pruning, and genetic variation within
scion cultivars.As a consequence, there have been numerous orchard systems described which

modify the display of the canopy in space and hence the light interception and distribution within
the canopy.There are several common threads to many of these modern systems:1) early
cropping, brought about by planting trees closely together on dwarfing rootstocks, ensuring high
light interception, 2) the maintenance of good light distribution within the canopy to ensure good
fruit quality and 3) maintenance of access for horticultural operations.Although apple tree
canopies have been and will be modified in the future, economic considerations will largely
determine the prevalence of particular systems within any one area of fruit growing.

REFERENCES
Cooper, J.P. 1975.Control of photosynthetic production in terrestrial systems.In
Photosynthesis and productivity in different environments.J.P Cooper, (ed.), Cambridge
University Press, pp. 593-621.
Jackson, J.E.1980.Light interception and utilization by orchard systems.Hort Reviews 2: 208-
267.
Palmer, J.W.1989.Canopy manipulation for optimum utilization of light.In Manipulation of
Fruiting.C.J. Wright, (ed.), Butterworths, London, pp. 245-262.
Wagenmakers, P.S. 1991.Planting systems for fruit trees in temperate climates.Critical
Reviews in Plant Sciences 10: 369-385.
Wünsche, J.N., A.N. Lakso, T.L. Robinson, F. Lenz and S.S. Denning.1996.The bases of
productivity in apple production systems: the role of light interception by different shoot
types.JASHS 121: 886-893.

Table 1.Effect of shade on apple flower bud development, fruit set and fruit quality.

Decrease

fruit weight

fruit red color
soluble solids concentration
bitter pit incidence and severity
sunburn
flower bud numbers

skin russet
fruit set

Increase

shrivel
fruit firmness

Table 2.Effect of shade on apple leaf structure and activity.

Decrease

leaf photosynthesis
leaf thickness

leaf cupping
leaf mass per unit