Ultrastructural localization of acid phosphatase during male meiosis and sporogenesis inDatura: Evidence for digestion of cytoplasmic structures in the vacuoles

Summary

Using a combination of electron microscopic and cytochemical techniques, the activity of the lytic enzyme acid phosphatase during male meiosis and sporogenesis inDatura innoxia Mill, has been followed. Evidence for digestion of cytoplasmic structures such as ribosomes and membranes during meiotic prophase and in the vacuolate microspores are presented. Before the onset of meiosis, acid phosphatase activity was observed chiefly in the walls of the pollen mother cell. During meiosis, due to the presence of a thick callose wall around the meiocytes, the enzyme activity could not be detected although the presence of numerous “autophagic type vacuoles” suggest lytic activity within these vacuoles. A positive reaction was, however, found in the adjacent somatic tissues. Also, low activity was observed in the small vacuoles of the young microspore, and the reaction was very intense in the large central vacuole of the old microspore which has a peripheral nucleus. In the young bicellular or mature pollen the activity was mainly observed in the small vacuoles. Other organelles showed no reaction. The significance of this cellular autophagy which is only observed at the meiotic prophase and at the vacuolate stage of the microspore is discussed, particularly in relation to the sporophyte-gametophyte transition.