Volume 45 Number 4 Article 8
Year 1991 Month 10
Title: Canopy Development, Photosynthesis, and Vegetative Growth as Affected by Apple Rootstocks
Authors: I. Schechter, D.C. Elfving, and J.T.A. Proctor
Abstract:
Fisheye photographs were taken in 1988 from
bud break to terminal bud formation under the
canopies of 'Starkspur Supreme Delicious' apple
trees on nine rootstocks in the 1980 NC-140
cooperative planting in Simcoe, Ontario.
Each
photograph was computer-analyzed for the per
centage of sky cover.
Rootstock affected the
amount of structural wood, the rate of canopy
development and the final leaf area.
However,
rootstock did not affect the pattern of canopy
development.
Photosynthesis (Pn) was measured
under field conditions using a LI-COR 6200
portable photosynthesis system.
Net Pn rates of
trees on cfwarfing rootstocks tended to be lower
than Pn rates of trees on more vigorous root
stocks.
Shoot leaves, spur leaves on spurs with
out fruit (S-F), and spur leaves on spurs with
fruit (S+F) from trees on on M.26 EMLA and
OAR 1 rootstocks showed no differences in Pn
rates due to rootstock.
However, for both root
stocks, shoot leaves had the highest, S+F the
lowest, and S-F leaves intermediate Pn rates.
Growth and yield components were assessed in
1987 and 1988, by harvest and defoliation of
sample branches.
Leaves were separated into
shoot and spur leaves when harvested.
Root
stocks strongly affected the number, area, and
dry weight of shoot and spur leaves as well as
the distribution between leaf types in both
years.
Rootstocks affected the number of spurs
per cm limb circumference.
Spur-leaf charac
teristics were correlated with yield efficiency
while shoot-leaf characteristics were correlated
with tree vigor.
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