XVI International Botanical Congess

In this report two mutations connected with disturbance in reproduction system of Zea mays - mac1 and pam1 are discussed. For mac1 were noticed underdeveloped anther and in ovule formation several archesporial cells, for pam1- formation of multinuclear megasporocytes. We noted similar ways of reproductive structures' development for mutants and normal plants. Under each archesporial cell a row of flat cells is formed. Megasporocytes increase and became elongated. Cells of epidermal layer of nucellus divide and form nucellar cap. Unlike of normal plants, both mutants form several archesporial cells, and expose variability of pathways of megasporocytes formation - with parietal cell separation or without. Megasporocytes of mac1 pass the meiosis asynchronously. Thus, in one ovule different stages of megasporo- and gametogenesis can be observed. The reduction of reproductive structures number takes place during ovule genesis. Only mature embryo sacs are fertilised, other stop their development and degenerate. In mature seed of mac1 only one embryo is present, as in normal plant.