LM, TEM AND SEM OBSERVATIONS OF ANTHER DEVELOPMENT IN THE GENIC MALE-STERILE (ms9) MUTANT OF CORNZEA MAYS

Abstract

The cytological development of the anther of the genic male-sterile ms 9/ms 9 of Zea mays L. was studied with the light microscope (LM), scanning electron microscope (SEM) and transmission electron microscope (TEM). Anther development in this mutant is indistinguishable from that in normal fertile material until the late Pre-Callose (Stage IIb) condition. At this stage, both at the LM level and in TEM views, the cytolysomes of PMCs and tapetum reveal densely staining bodies (DSBs) which frequently appear to surround portions of cytoplasm. These DSBs are double membrane bounded and frequently associated with ER. PMC degeneration begins prior to meiosis though tapetal cells remain intact until the equivalent of the Near Mature Pollen Stage (VIII). Tapetal cells of ms 9/ms 9 material, following mitosis, frequently develop thin walls between the two nuclei. We conclude that the DSBs represent a class of lysosome called autophagic vacuoles or cytolosomes. It is not clear whether they are elaborated directly in response to the mutant allele or perhaps represent a cytological response to genetically based abnormal biochemistry. Despite the early failure of PMCs and tapetal cells, epidermal cells of ms 9/ms 9 anthers develop cuticular ridges quite similar to those formed on normal fertile anthers.