The multinucleate condition in fibers of tobacco

Abstract does not appear. First page follows.

Introduction

The occurrence of a multinucleate phase in the development of fibers, although rarely mentioned in literature, is a known fact (Eames and MacDaniels, 1925), p. 56). It was apparently established by (Treub (1880)), who reported that phloem fibers are multinucleate in many angiosperms and that this condition results from division of nuclei without subsequent formation of cell plates.

The multinucleate fibers of tobacco were noted in connection with certain investigations on the phloem of this genus (Esau, 1938). A somewhat detailed study of these fibers seemed of interest, because occasionally writers report multinucleate condition in healthy or diseased cells without giving convincing evidence to support their contention.

The fibers of tobacco were studied in stems and leaves of Nicotiana tabacum L. and Nicotiana glauca Graham. As in the previous work (Esau, 1938) the material was killed in chrom-acetic-formalin solution and was imbedded in paraffin after a dehydration in butyl- and ethylalcohol mixtures. The illustrations were prepared from slides stained following Heidenhain’s schedule.

Results

As was shown in the paper on phloem of tobacco (Esau, 1938), the multinucleate fibers of this genus arise from procambium among primary sieve tubes and are, therefore, interpreted as primary phloem fibers. These elements occur in the internal as well as external phloem and differentiate in the elongating portion of the stem or leaf.

During the elongation of the fibers their nuclei divide mitotically (plate 2, A), with splitting of chromosomes and formation of normal daughter nuclei. The karyokinesis is not, however, followed by cytokinesis. In the ordinary cell division the cell plate becomes clearly evident before the daughter nuclei emerge from the telophase (plate 1, A), whereas in the fibers no cell plate is developed (plates 1, B; 2, B and C). The spindle fibers are less persistent than in ordinary division figures and gradually disappear during late anaphase and telophase (plates 1, B and 2, C).