MARSOLAIS, A. A , , WILSON, D. P. M., TSUJITA, M. J . , and SENAKATNA, T. 1991. Somatic clnbryogenesis and artificial seed production in Zonal (Pelnrgoniutt~ X I~ortor~rrn) and Regal (Pelor-goniutn X dotne.sticurn) geranium. Can. J . Bot. 69: 1188-1193. Somatic embryos have been produced from petioles and hypocotyls of Zonal geranium and from petioles of Regal geranium. Somatic embryos of both species have been desiccated and subsequently germinated. Some important factors that influence the rate of somatic embryo production in geranium arc discussed. They include culture medium factors such as auxin and auxin dosage, carbohydrates, amino acids, pH, and basal medium composition. The donor plant genotype also appeared to have an effect on somatic embryogenesis and survival after desiccation.

The effect of the auxin phenylacetic acid (PAA) on wheat anther and on barley anther/microspore culture was investigated. With PAA the induction response was not usually significantly different from controls but a significantly higher number of green plants were produced in wheat anther and barley microspore culture. For wheat anther culture 100 mg/L PAA was beneficial. For barley microspore culture the optimum levels were from 1 to 100 mg/L, depending on genotype. In barley anther culture there were no improvements using PAA. In wheat anther culture, 145 green plants/100 anthers were obtained with cultivar Veery'S', while the average response from twelve F1 hybrids in the breeding program was 332 green plants/100 anthers. At least 1000 green plants were obtained using isolated microspores from 100 anthers in barley cv. Igri. With cv. Bruce, regeneration occurred only when 100 mg/L PAA was used. The influence of PAA appears at the embryogenic phase of the culture system. The possible mechanisms by which PAA may improve regeneration are discussed.

Microspore segmentation in anthers of the barley line C4-13 cultured on a modified N6 medium was followed for 10 days to examine the routes to multicellular structure formation and origin of nonhaploid chromosome numbers. The first division of the uninucleate microspores gave rise to two similar nuclei or a large vegetative and a small generative cell. The two similar nuclei divided independently and both contributed to the formation of multicellular structures. Independent division of the vegetative and generative cell, and division of the vegetative cell alone resulted in two other pathways to multicellular structure formation. Nuclear fusion and endomitosis occurred in some pathways and appeared to be involved in ploidy variation. In addition, a very low frequency of fusion between the nuclei of two microspores was observed. This event may account for the occasional presence of heterozygosity in microspore-derived plants.Key words: barley (Hordeum vulgare), anther culture, androgenesis, ploidy level, nuclear fusion, endomitosis, gene expression.

A medium and replenishment technique for the production of large numbers of calli from anthers of the barley cultivar Elrose is described. The barley anther culture basal medium supplemented with 8 mg/L 2,4-D and 9% sucrose and replenished at 10-day intervals with basal medium containing 1 mg/L indole acetic acid and 3% sucrose was optimal for anther response (21.0%) and productivity (67 calli per 100 anthers plated).

A number of media constituents including sucrose, ammonium nitrate and plant growth regulators were evaluated in an attempt to improve somatic embryo production in zonal geranium (Pelargonium x hortorum) cv. Scarlet Orbit Improved. Somatic embryo production was characterized by the quantity and type of somatic embryo induced by the treatments. Sucrose at 4% supported the highest number of total somatic embryos while improving the proportion of the morphologically normal cotyledon-stage somatic embryos. Addition of ammonium nitrate also improved embryo production. With 1.89 mM ammonium nitrate, normal cotyledon-stage embryo development was increased by 53%; the proportion of normal cotyledon-stage embryos decreased and abnormal embryos with leaves or serrated margins in cotyledons (fringed-shoot type) increased with higher ammonium nitrate concentrations. The effect of plant growth regulators on somatic embryogenesis indicated that exogenous supply of indole-3-acetic acid (IAA) at a range of 0.25 to 4/zM failed to promote somatic embryogenesis. In contrast, benzyladenine (BA) up to 2.0 #M increased the total embryo number and the proportion of desirable cotyledon-stage embryos. There was no interaction between IAA and BA. Our research has demonstrated that improvement in both quantity and quality of somatic embryos can be achieved in zonal geranium.