Submitted to: In Vitro Cellular And Developmental Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 10, 2002
Publication Date: December 1, 2002
Interpretive Summary: Plant somatic embryogenesis is the phenomenon where a normal cell in plant tissue culture is induced by chemicals to form an embryo, the same sort of embryo that forms in a developing seed. The advantage of forming embryos from normal nonsexual cells (e.g., leaf cells) is that all the embryos are exactly alike (i.e., clones) and are therefore useful for large-scale propagation of that plant. In essence, this is the use of tissue culture to produce "artificial" seed. "Artificial" because the embryos are not produced via the fusion of sperm and egg cells. To produce large numbers of somatic embryos for propagation it is necessary to produce embryos that are phenomenon where normal somatic embryos capable of germination were obtained when citrus tissue cultured cells were grown on a semi-permeable membrane of cellulose acetate.
Technical Abstract: Development of citrus somatic embryos initiated from embryogenic callus generally results in abnormal morphologies during growth and development. Shoots can be regenerated by organogenesis from these abnormal structures, excised and rooted to recover plants. To normalize development, glycerol-induced globular stage somatic embryos of sweet orange were cultured on cutoff cellulose acetate, cutoff cellulose acetate, nitrocellulose, polyvinylidene fluoride (PVDF), cellulose filter paper, positively charged nylon, or neutrally charged nylon membranes. Only globular stage embryos cultured on semi-permeable cellulose acetate membranes developed normal, 2-cotyledon, bipolar, heart-shaped embryos, and did not develop any aberrant teratoma-like structures. Heart-shaped embryos were developed and germinated on then transferred to a soilless mix. Culture of embryogenic callus directly onto cellulose membranes also resulted in the development of normal heart-shaped embryos indicating that glycerol induction of globular stage embryos is not necessary. Heart-shaped embryos were not observed when the osmatic potential of the medium was increased by the addition of polyethylene glycol (PEG); neither were they observed when the matric potential of the medium was increased by increasing the gelling agent concentrations of agar and Gelrite.