Growth and metabolism of cells and tissue of jack pine (Pinus banksiana). 7. Observations on cytoplasmic streaming and effects of L-glutamine and its analogues on subcellular activities

Abstract

Cells from jack pine (Pinus banksiana Lamb.) callus and suspension cultures were observed by cinemicrography to evaluate cytoplasmic streaming, motion of organelles, and nuclear behaviour under glutamine stress. Streaming rates were greatest in the largest cells. Rates were reduced in smaller cells, where transvacuolar strands were not as prominent and displacements of organelles were not strongly affected by cyclosis. During increased rates of cytoplasmic streaming, chloroplasts tended to associate with each other and mitochondria often changed direction and shape.The addition of 400 ppm L-glutamine to a defined basal medium increased the linear velocity of organelles from 2-7 microns (μ)/s to 7–12 μ/s, whereas D-glutamine eventually stopped cytoplasmic streaming, with a concomitant increase in nucleolar size. While additions of low levels of α-N-acetyl-L-glutamine and isoglutamine stimulated streaming, this occurred usually without other significant morphological effects. Cytoplasmic movements that were induced by exposure of cells to L-glutamine were intimately involved with the fine strands and with nuclear and nucleolar behavior. Movements ceased when strands were disrupted under nutritional stress and by inhibitory responses to D-glutamine.