THE LENGTH, TANGENTIAL DIAMETER, AND LENGTH/WIDTH RATIO OF CONIFER TRACHEIDS

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Abstract
In the gradual enlargement of tracheid dimensions which takes place outward from the pith in the stem and branches, growth in cell length outstrips that in tangential width so that the length/width ratio rises. Largest tracheids are usually found in the inner wood of lateral roots, where the length/width ratio is highest. Interspecific and interregional differences follow a similar pattern of relationship with respect to cell dimensions. As a rule, species or races which inhabit unfavorable sites have comparatively small cells with a low length/width ratio. Species which populate better sites and have greater growth potential are characterized by longer cells and a higher length/width ratio. Indications exist of a positive relationship between height growth, tracheid length, and the length/width ratio. On the other hand, increased radial growth in mature trees is accompanied by reduction in mean cell length and a lowering of the length/width ratio.