Cytoplasm is the fluid material encased by the plasma membrane of a cell. Cytoplasm does much of the work of a cell by moving intracellular organelles. Cytoplasm is a heterogeneous material that is able to change its viscosity. Cytoplasmic streaming is the flowing movement of cytoplasm, internal and external to the plant cell, in a rapid orderly fashion. In plant cells, cytoplasmic streaming carries chloroplasts, which are the sites of photosynthesis, from one part of the cell to another. This helps maximize photosynthesis and subsequent cell growth. The objective of this experiment was to observe cytoplasmic streaming in the aquatic plant Elodea by low power microscopy.
Cytoplasmic streaming was observed on the 11th day of the Skylab 4 mission. During the second observation, streaming was not observed and the plants were reported to have died. The film was unproperly exposed, thus, the only information came from crew observations. It was thought that in addition to the problem of excessive dark periods, it may have been difficult for waste products to diffuse away from the leaf surface in weightless conditions. Therefore, Elodea may have been smothered in oxygen, unable to obtain the necessary carbon dioxide for photosynthesis.