engleski

Protoplasts allow tracking of early somatic embryo development in the conifer

Protoplasts of hybrid larch (Larix x eurolepis Henry) were separated from embryonal-suspensor tissue by discontinuous density gradient centrifugation. Three fractions were obtained consisting mainly of (1) large, vacuolated non-cell regenerating suspensor protoplasts and cytoplasts, (2) mononucleate cell- and somatic embryo-regenerating protoplasts and (3) multinucleate non-cell regenerating protoplasts. Protoplasts were immobilised in thin films of alginate and cultured on a medium sustaining embryo development. In analogy to the partitioning of free nuclei during early prophase in zygotic embryogeny or during formation of the megagametophyte, as is known in the Pinaceae, it was hypothesised that compartmenting of nuclei in a multinucleate protoplast by cell wall formation might result in the direct inception of an embryo or embryogenic tissue. However, this was not observed. A protoplast containing two, three or four nuclei might undergo mitosis and cytokinesis, but only as a result of one of the nuclei dividing and entering the cell cycle and only when nuclear division had been preceded by cell wall resynthesis. The possibility of separating somatic embryogenic protoplasts from others of different lineages aids the study of the cryptic potential of these cells in their apparent simulation of zygotic embryogeny. By further immobilising and culturing an enriched population of potentially embryogenic protoplasts it becomes possible to track some of the early steps in somatic embryo development.

protoplasts; somatic embryos; hybrid larch; zygotic embryogenesis

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