Cine‐photomicrography of Low Temperature Effects on Cytoplasmic Streaming, Nucleolar Activity and Mitosis in Single Tobacco Cells in Microculture

Abstract

Living, unstained, single tobacco (Nicoliana tabacum × N. glutinosa) cells (clone H‐196) were grown in microcultures in liquid medium containing sucrose, mineral salts, coconut milk and 2,4‐dichlorophenoxyaeetic acid. Time‐lapse motion pictures were taken through interference and phase microscopes. The movement of cytoplasm and cell organelles gradually slowed and ultimately completely ceased as the cell was cooled by dry ice. The cessation of the movement of cell organelles took place between 5 and –7C. The typical cytoplasmic morphology was lost as the movement slowed. The cytoplasmic strands thinned out and numerous small vacuoles formed. During rewarming of the cell to room temperature, the vacuoles were replaced by numerous small globular masses of cytoplasm which reorganized into cytoplasmic strands. The normal movement of cytoplasmic strands and cell organelles was resumed. A number of small nucleolar vacuoles at room temperature gradually expanded and coaleseed to form a large central vacuole which underwent further expansion and then contracted rapidly. Four different concentric zones were visible across the nucleolar region. A white, highly reflecting, glossy substance appeared on the surface of the expanding vacuole. The position of the nucleus during contraction and expansion was never stationary. Some nucleolar vacuoles remained open for an indefinite period of time when the cell was cooled to 5C. No change was noticed during cooling, but during rewarming to room temperature, the nucleolar vacuole was partially closed. The pumping action of the nucleolar vacuole suggested important exchanges of metabolites between the nucleolus and the cytoplasm. A single cell of tobacco did not divide at –10C, but mitosis proceeded upon cooling the cell to – 12–15C for a brief period. Different phases of mitosis, specifically formation of the cell plate, cell wall, and separation of nuclei, were delayed by low temperature treatment.

Responses to Extreme Temperatures. Cellular and Sub-Cellular Bases

“…For example, protoplasmic streaming rapidly ceases (LEWIS 1956) or is greatly reduced (PATTERSON and GRAHAM 1977) at temperatures around 10 to 12°C in chilling-sensitive species and is associated with altered cytoplasmic morphology such as thinning of transvacuolar strands and the formation of numerous small vesicles (DAS et al 1966) which occur within seconds (PATTERSON et al 1980).…”

Temporary Inhibition of Translocation Velocity and Mass Transfer Rate by Petiole Cooling

“…et al (1) have reported a number of cytoplasmic changes during cooling in tobacco cells in the range of 5 to -7 C. Tilney and Porter (9) reported the disappearance of microtubules from the axopodia of a protozoan and formation of short tubules as a disintegration product at a temperature of 4 C. Sieve tubes contain various fibrillar structures known as P-protein. It may be that these structures, like those discussed above, disintegrate or undergo a change in form at low temperatures, leading to an increased resistance to flow through the sieve tubes.…”

Suppression effect of CIPC on nucleoli in Vicia faba root tip cells.

“…Squash preparations of root tips ordinarily show the nucleoli which have uniformly in termingled contents with some vacuolar inclusions, and a distinct encircling light zone called the "nucleolar halo" (Kordan 1964, Das et al 1966), (Fig. 2a).…”