MULTICELLULAR POLLEN FORMATION IN CULTURED BARLEY ANTHERS .1. INDEPENDENT DIVISION OF THE GENERATIVE AND VEGETATIVE CELLS

Multicellular pollen units partitioned into embryo- and endosperm- or possibly suspensor-like components are formed in barley (Hordeum vulgare cv. Sabarlis) anthers cultured from spikes excised during the free spore phase of microsporogenesis. The embryo-like component may be derived from the generative cell, the vegetative cell, or from contributions of both cells, and appears to be usually, though not invariably, haploid. The endosperm- or suspensor-like component is derived from the vegetative cell and rapidly becomes non-haploid or mixoploid. The initial pattern of division often simulates that in the formation of 4-celled and 7-celled embryo sacs. The time of excision during the free-spore phase is critical. Partitioning occurs only with excision during the mid-unicellular stage (stage 2) when the nuclei are probably still in the pre-DNA replication phase, but excision at the early unicellular stage (stage 1) in ineffective and leads to rapid degeneration of the spores. With excision at the late-unicellular stage (stage 3), independent contribution by the generative cell is blocked and the pollen develops by the known A, B, or C pathways. Temperature stress given to the excised spikes before culture of the anthers enhances the frequency of partitioned units but is thought not to be causal. It is suggested that the multiplicity of developmental pathways may have some bearing on whether the plantlets ultimately produced are albino, variegated, or green. © 1979 Oxford University Press.