Cytoplasmic streaming, or cyclosis, is an energy-consuming event that occurs in plant cells and is used to distribute nutrients in the cytoplasm. It is common in larger cells, such as sieve tube elements, where diffusion is not adequate for substance distribution. In plants, it may also be used to distribute chloroplasts for maximum light absorption for photosynthesis. Scientists do not yet understand how this process occurs, although it is hypothesized that micro-tubules and micro-filaments play a role, interacting with the motor proteins of organelles.
Using one small leaf of Elodea, prepare a wet mount. View the slide under high power and identify the chloroplasts. Wait a few minutes. This will allow the cells to be heated by the light of the microscope. Now you should be able to see the chloroplasts cycling around the central vacuoles of cells. Does this occur in the same direction in all cells or is the movement random?