The Formation of Chromoplasts in Fruits of Cucurbita maxima Duch. 'Turbaniformis'

The ultrastructure of chromoplasts of Cucurbita maxima 'turbaniformis' was investigated in different stages of development. Young unripe fruits contained chloroplasts. During fruit ripening the grana disappeared while the thylakoid plexus was forming. The latter diminished in later stages while a peripheral reticulum and numerous tubules appeared. Tubules were located either in bundles near the border or singly among numerous plastoglobules in the middle of the chromoplast. Some tubules were in contact with plastoglobules. In the chromoplasts of an old ripe fruit only numerous tubules are present. Observations are discussed with special reference to the origin of chromoplast tubules.