Immunofluorescence Microscopy of Microtubule Arrangement in Root Cells of Pisum sativum L. var Alaska

The arrangement of wall microtubules (MTs) in Pisum sativum roots was viewed immunofluorescently using cryosectioning. Most cells in the tip region of pea roots (0–2 mm from tip) had wall MTs arranged transversely to the root axis. In the region elongating at a higher rate (2–4 mm), wall MTs of epidermal, cortical and stelar cells were all transversely arranged. In the region of about 5 mm from the tip, in which cell elongation had already ceased, wall MTs in cortical cells changed from a transverse to an oblique arrangement in relation to the root axis. Some cells had a crossed arrangement of wall MTs, which was interpreted as representing two sets of unidirectional, oblique wall MTs in opposite cell cortices of a single cell. This change was completed within a region of 1-mm width. Since roots elongated at a rate of 0.6 mm h−1, it means that the arrangement of wall MTs changed within 2 h. An oblique arrangement of wall MTs was also observed in stelar cells. As the cells aged, the oblique arrangement tended to change to a steeper or even a longitudinal one.