Defoliation and nitrogen effects on photosynthesis and growth of Eucalyptus globulus
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posted on 2024-09-17, 02:05 authored by E Pinkard, M Battaglia, Caroline MohammedCaroline MohammedPlant responses to defoliation are complex. We established a field experiment in a nine-month-old Eucalyptus globulus Labill. plantation to examine the effects of pattern (upper crown versus lower crown removal), frequency (single, double or triple defoliation within a 12-month period) and severity (25 versus 38% of leaf area removed) of defoliation and the effect of soil nitrogen (N) on photosynthetic processes and stem growth. The photosynthetic responses observed following defoliation could be attributed to changes in source:sink ratios. Light-saturated CO2 uptake (Amax) increased with increasing severity and frequency of defoliation irrespective of defoliation pattern. Seedlings defoliated in autumn did not exhibit increases in A max until the following spring, whereas there was no such delay in photosynthetic responses associated with spring defoliation. Application of N before defoliation allowed trees to compensate for the effect of defoliation on stem diameter growth, which could not be explained simply in terms of increases in Amax. The observed increases in stem diameter increment following N fertilization of defoliated trees suggested increases in leaf area development, and there were changes in the leaf area: leaf dry mass ratio that may have increased light absorption by the crown. Nitrogen fertilization also increased partitioning of dry mass to branches at the expense of main stems, suggesting that N supply was important in rebuilding crowns following a defoliation event. © 2007 Heron Publishing.
History
Publication title
Tree PhysiologyVolume
27Issue
7Pagination
1053-1063ISSN
0829-318XDepartment/School
College Office - CoSE, Agriculture and Food SystemsPublisher
Heron PublishingPublication status
- Published
Place of publication
CanadaSocio-economic Objectives
269999 Other plant production and plant primary products not elsewhere classifiedUsage metrics
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