The Effect of Water Stress on Sorghum Bicolor L. Moench: A Stereological Study of Bundle Sheath Cells

Sorghum leaves from plants grown under irrigated and dryland field conditions were used. The leaves from stressed plants had smaller leaf areas and they were thicker than the leaves from nonstressed plants. The bundle sheath cells occupied about 13% of the leaf area in both nonstressed and stressed plants. Leaves from stressed plants had smaller but more numerous bundle sheath cells. It was concluded that the reduced leaf area in the stressed plants was due to a sensitivity of cell enlargement to water stress and that cell division was not affected.

Stereological analysis of bundle sheath cells from nonstressed and stressed plants was used to study differences in the cell wall, cytoplasm, chloroplasts, starch granules, chloroplast lipid bodies, mitochondria and central vacuole. The total volumes showed a decrease in the cell wall, cytoplasm and central vacuole of the bundle sheath cells of stressed plants. In the same cells the chloroplasts were reduced in number but individual chloroplasts showed no change in volume. In stressed plants the starch granules were both smaller and fewer in number whereas the chloroplast lipid bodies were the same size but fewer in number. The mitochondria were both smaller and fewer in the leaves from the stressed plants. On a per leaf basis the chloroplasts were reduced both in volume and number but only mitochondrial volume was reduced.