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Needle anatomy changes with increasing tree age in Douglas-fir
Martha Apple1, Ken Tiekotter, Michael Snow
1Department of Forest Science, Oregon State University, Corvallis, OR 97331, USA. mapple@unr.edu
Tree Physiology
|February 7, 2002
Summary
Douglas-fir (Pseudotsuga menziesii) needle anatomy changes with tree age. Sapling needles have less photosynthetic area, potentially impacting growth rates in older trees.
Area of Science:
- Forest Ecology
- Plant Anatomy
- Woody Plant Physiology
Background:
- Morphological differences are observed between old-growth Douglas-fir trees and saplings.
- These differences may extend to variations in needle anatomy, impacting physiological functions.
Purpose of the Study:
- To compare and quantify anatomical parameters in Douglas-fir needles across different tree ages.
- To investigate developmental changes in needle anatomy associated with increasing tree age.
Main Methods:
- Microscopy and image analysis were used to examine cross sections of previous-year needles.
- Needle anatomy was compared between old-growth trees and saplings at multiple sites.
- A chronosequence of trees (10, 20, 40, and 450 years old) was analyzed.
Main Results:
- Significant anatomical differences were found between sapling and old-growth Douglas-fir needles.
- Sapling needles were longer with smaller vascular cylinders, larger resin canals, and fewer hypodermal cells.
- Astrosclereids were abundant in old-growth needles but scarce in sapling needles, resulting in 11% less photosynthetic area in older trees.
Conclusions:
- Needle anatomy undergoes developmental changes with increasing Douglas-fir tree age.
- The increase in non-photosynthetic area with age may contribute to reduced growth rates in mature trees.