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- Author or Editor: Mark A. DenHerder x
Defoliation by pests was simulated with potted tree model systems and field-grown trees. `Redchief'/M.7 apple trees were grown in 10 1 pots as a single shoot. Forty-five days after 25%, 50%, or 75% removal of apical or basal leaf number, new leaf dry weight (produced after treatment) was 23%, 53%, and 45% higher, respectively, for apically treated trees, and -7%, 61%, and 64% higher for basally treated trees, than control trees. Root dry weight was reduced by as much as 59% (apical 75% removed). Photosynthesis following 75% leaf removal was inhibited 1 day after treatment, but increased above the control within 3 days. However, by 35 days after treatment photosynthesis had declined to 53% of control. Leaf removal (50%) June 15 (1990) of 4-year old `Early Granny'/Mark increased net photosynthesis by 40% within 8 days of treatment. Trunk cross-sectional area increase of June- and twice-(June 15 and July 30) defoliated trees was 35% of control trees. Leaf nitrogen content (% dry wt.) in September was 1.75 for twice-defoliated trees compared to 1.58 for control trees.