Variations in the Size of Mitotic Cells in the Root Meristem

A. E. Dobrochaev and V. B. Ivanov

Timiryazev Institute of Plant Physiology, Russian Academy of Sciences,
Botanicheskaya ul. 35, Moscow, 127276 Russia

Received December 21, 2000; in final form, March 16, 2001

Abstract—Variations in the length of mitotic and interphase cells were analyzed in various tissues of wheat
roots and in the cortex of maize roots. Reliable differences were shown in the length of mitotic cells in individ-
ual file clones of cells of the same tissue. The mean lengths of dividing cells in different roots differed to a lesser
extent than those of different files in the same tissue of one root. Within the file, the length of the sister simul-
taneously dividing cells differed the least, while the difference of lengths of the neighbor simultaneously divid-
ing nonsister cells was bigger. The mean length of interphase cells in any file was always less than that of mitotic
cells by a factor of 1.45. This ratio was almost invariable for files and tissues in both the plants we studied and
corresponded to that of an exponentially growing cell population. In addition, a very small number of cells were
found (less than 1%) in meristems, which are longer than the mitotic cells. The length of these cells exceeded
those of mitotic cells by less than twice. The origin of such cells is discussed. The length of mitotic cells near
the quiescent center is more variable than in the middle of the meristem in the cortex of both plants. In the mer-
istem basal part, the mitotic cells were no longer than those in the middle of the meristem but there were no
small dividing cells. In the wheat epidermis, the cells are differentiated into trichoblasts and atrichoblasts and,
therefore, the length of the dividing cells is highly variable. The cell length is essential for their transition to
mitosis for all studied proliferating meristem cells.

Key words: mitotic cycle, root meristem, cell proliferation, critical size, sister cells, whet, maize

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