The problem of giant cells in biology.

Abstract

The influence of geomagnetic field (GMF) outbursts on the cellular structure of root apices of Allium cepa L. was established. The tips of roots and shoots were fixed twice per day during a 24-day period. Abnormal binuclear, tetranuclear cells, large cells with large nuclei, and giant cells with giant nuclei were observed in the meristem zones of the root apices. They were surrounded by mononuclear diploid cells. Within some days of the experiment, the amount of polynuclear cells comprised as much as 20% of all the meristem cells. The graphical presentation of this process shows peaks and troughs in the number of polynuclear cells. By comparing this with the changes in the GMF characteristics at the same days, we found a striking correlation between the two. The in vitro experiments on isolated root tip meristems allowed us to exclude the possibility of centralized regulation of cell structure changes being affected by the mutual exchange of metabolites between organs of the whole plant. The artificial screening of the GMF led to a significant decrease of cells with enhanced nuclear DNA content. The same plant cells demonstrated greater sensitivity to fluctuation of GMF under geographical conditions of high-latitude.

1. Introduction

It is well known that plant development is determined mainly by the functional activity of the meristems. Meristems are the most sensitive tissues that form the plant body. The sustainability of the meristems determines the resistance of the whole plant to harmful influences from the environment. (1) In our publications, we have shown that the cell structure of the root meristem of Allium cepa L. and several species of Triticum L. can be changed under the influence of the geomagnetic field (GMF). (2,3,4,5) On particular days, the peak values, phases, and periods of oscillations (frequencies) of GMF constantly vary. During the periods of sharp GMF outbursts- called magnetic storms, the polynuclear cells, large cells with large nuclei and giant cells with giant nuclei appear among the regular meristematic cells. The appearance of these cells is initiated suddenly and continues during two-three days. Usually polynuclear, these large and giant cells appear distributed as single cells. These new cells are not organized in strings or clusters. They do not become the initiators of gistogenesis. Polynuclear, large and giant cells are absent in the areas of the absorption zone of the root. In some large and giant cells, we observed the fragmentation and disintegration of the nuclei.

Production of cells with enhanced DNA content, or endo-reproduction, takes place in differentiated and functionally active tissues of plants and animals. (6,7) In our experiments, we confirmed the appearance of such giant cells in primary meristems of the zone of cell division in the root, where the cell differentiation did not take place. We demonstrated for the first time the primary role of the GMF in the initiation of the giant cells. This observation indicates the fundamental importance of the study of plant giant cell production under the influence of GMF. Results of our investigation in this field during the period from 1991 until 2002 are explained in 25 publications, mainly in Russian.

2. Cosmic Factors and Plant Adaptation

Our studies have shown that the cause of the appearance of giant …