Needle anatomy changes with increasing tree age in Douglas-fir

Abstract

Morphological differences between old-growth trees and saplings of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) may extend to differences in needle anatomy. We used microscopy with image analysis to compare and quantify anatomical parameters in cross sections of previous-year needles of old-growth Douglas-fir trees and saplings at the Wind River Canopy Crane site in Washington and at three sites in the Cascade Mountains of Oregon. We also compared needle anatomy across a chronosequence of 10-, 20-, 40- and 450-year-old Douglas-fir trees from the Wind River site. Anatomy differed significantly between needles of old-growth trees and saplings at all sites, suggesting a developmental change in needle anatomy with increasing tree age. Compared with needles of old-growth trees, needles of saplings were longer and had proportionately smaller vascular cylinders, larger resin canals and few hypodermal cells. Astrosclereids, which sequester lignin in their secondary cell walls and occupy space otherwise filled by photosynthetic cells, were scarce in needles of saplings but abundant in needles of old-growth trees. Needles of old-growth trees had an average of 11% less photosynthetic mesophyll area than needles of saplings. The percentage of non-photosynthetic area in needles increased significantly with increasing tree age from the chronosequence of 10-, 20-, 40- and 450-year-old trees at the Wind River site. This reduction in photosynthetic area may contribute to decreased growth rates in old trees.

Changes in Gene Expression in Needles and Stems of <i>Pinus radiata</i> Rootstock Plants of Different Ontogenic Age

“…Quicker and earlier response in younger 1-year-old cuttings and higher rooting rates, are in agreement with several researches that indicate that capability for rooting is lost between 3 and 5 year old in gymnosperms [6] [10] [11] [25] [26]. Anatomical changes observed in both types of needles are in agreement with reports in Douglas-fir and P. halepensis [27] [28], indicating anatomical differences between young and old needles. Needles from younger trees presented a smaller vascular cylinder and increased mesophyll area.…”

Relationship between MdMADS11 Gene Expression and Juvenility in Apple

“…Leaf thickness and chlorophyll content appear to increase during the transition from the juvenile to adult phase in tree species (Greenwood, 1995;Greenwood et al, 1989;Poethig, 1990). These changes may increase the photosynthetic rate per leaf during the phase transition, resulting in higher assimilated productivity per tree in adult trees (Apple et al, 2002). In this study, leaf area and the SPAD value increased from A to F in Figure 2d and e, suggesting an increase in the photosynthetic rate per leaf.…”

Sources of within- and between-stand variability in specific leaf area of three ecologically distinct conifer species

“…Increasing stand age was associated with greater SLA, perhaps due to the effects of lower water potentials and greater water stress on the [1] found that needles in young saplings (∼10 years-old) were longer and had proportionately smaller vascular cylinders, larger resin canals and few hypodermal cells when compared to needles on mature trees (∼450 years-old). In addition, mean needle thickness was ∼9% lower when needles from 20 to 40 years-old trees were compared to mature trees [1]. Kennedy [18] found that specific leaf weight (1/SLA) in the upper canopy of Douglas-fir and lodgepole pine (Pinus contorta var.…”