Multicellular Pollen Formation in Cultured Barley Anthers

Patterns of nuclear and cellular division leading to the formation of haploid, non-haploid, and mixoploid multicellular pollen grains in cultured anthers of Hordeum vulgare cv. Sabarlis are described. The vegetative cell divides either by repeated unequal haploid divisions (A pathway) or by synchronous nuclear divisions accompanied by fusion and variable wall formation (non-haploid and mixoploid). The divisions are random and unorganized. The generative cell degenerates or is integrated into the vegetative component either before or after division has commenced. Prior fusion (C pathway) leads to binucleate or bicellular diploid units partitioned by a straight transverse wall. These binucleate and bicellular units are cytologically indistinguishable from other diploid units derived from spores which do not form a generative cell (B pathway). Division of the bicellular units may be random and unorganized, but in some instances the two cells divide synchronously and in a highly ordered manner yielding embryonic-like octants of cells. The diploid binucleate units generate still higher ploidies with or without wall formation. The significance of the various segmentation patterns is discussed in relation to previous concepts of pollen-callus formation.