Somatic Embryo Ontogeny in Suspension Cultures of Orchardgrass

Abstract

Orchardgrass ( Dactylis glomerata L.) is the only known grass or cereal species in which somatic embryos fully develop to a germinable stage directly in a single liquid medium. The objectives of the present investigation were to document and detail the developmental pattern of these embryos and to compare their size and structure to zygotic counterparts. Suspension cultures were initiated and mainrained in Schenk and Hildebrandt medium containing 30 μM dicamba (3,6‐dichloro‐o‐anisic acid) and 3 g L −1 casein hydrolysate. The suspension was passed through a 120‐μm sieve resulting in a culture composed of single cells and small cell masses. Somatic embryos that were identical in structure and size to zygotic embryos occurring in mature caryopses developed from these cells directly in the liquid maintenance medium. The developmental pattern was indirect embryogenesis. Embryos differentiated and were released from clumps of embryogenic cells (proembryonal complexes). This pattern is analogous to that in suspension cultures of certain dicotyledonous species, e.g., carrot ( Daucus carota L.). Fully developed embryos were germinated and resulting seedlings grown to mature plants.