Sieve Cell Differentiation; Accurate Determination by Polarized Light

Abstract

Differentiating sieve cells can be qualitatively and quantitatively determined in white pine or other species of plants with phloem cells possessing nacreous primary walls or thickened secondary walls. Transverse sections from stained and unstained preparations of white pine examined in polarized light reveal a distinct zone of birefringent sieve cells situated between the cambial zone and layer of seasonal phloem parenchyma. The deposition of secondary walls in sieve cells in pine and their unequivocal recognition in polarized light presents a simple, effective means for detecting newly differentiated sieve cells and for quantitatively estimating their production during an experimental period.