© 1992 Heron Publishing—Victoria, Canada
Root growth and carbohydrate responses in bearing citrus trees following partial canopy removal
D. M. Eissenstat and L. W. Duncan
Citrus Research and Education Center, University of Florida—IFAS, 700 Experiment Station Road, Lake Alfred, FL 33850-2299,
USA / Received August 8, 1991
Summary
In August, eight 4-m tall citrus trees were pruned by removing the top third of their canopy. Eight unpruned trees served
as controls. Root growth, which was examined nondestructively with minirhizotrons over a four-month period, tended to be less
in the pruned than unpruned trees seven days after pruning and this difference was significant (P < 0.05) from 14 to 49 days after pruning. Total reducing and ketone sugars (includes free fructose, sucrose and fructans)
in the fine roots were less in pruned than unpruned trees 20 days after pruning, but not thereafter. By 30 days after pruning,
at least 20% of the roots of the pruned trees at a soil depth of 9 to 35 cm apparently died. By 63 days after pruning, root
length density had recovered to that of the unpruned trees, although starch reserves were 18% less in the fine roots of pruned
than unpruned trees at this time. Nine to eleven months after pruning (May to July), total biomass of leaves and fine roots
to a depth of 1 m were similar in pruned and unpruned trees. However, fruit biomass harvested in April from pruned trees was
only 24% of that in the unpruned trees. In May, nonstructural carbohydrates in the fine and coarse roots of pruned trees were
generally greater than in unpruned trees, possibly reflecting previous differences in fruit production.
