ABSTRACT
Gravity is the most constant and ubiquitous environmental stimulus that influences evolution and growth of plants. Cells of root caps of seedlings grown in microgravity usually allocate more volume to lipid bodies and hyaloplasm and less volume to mitochondria, dictyosomes, and plastids than those of Earth-grown seedlings. Gravity drastically reduces the number and relative volume of dictyosomes in cells of root tips that produce mucigel. Cell walls are a plant's primary means of withstanding gravity. Since cell walls are deposited by dictyosomes, the reduced allocation of dictyosomes in cells of roots also affects the deposition and structure of cell walls. Cellular and subcellular studies of the effects of gravity on roots also suggest that gravity affects the energy metabolism of roots. Cells of roots grown in microgravity contain significantly more lipid bodies than Earth-grown controls.
