Ultrastructural characteristics of an achlorophyllous callus line ofLotus corniculatus

Abstract

An achlorophyllus isoline originated spontaneously from a green callus line derived from a genotype ofLotus corniculatus L. cv. Leo. This isoline is characterized by significantly faster callus growth than the green line and by differentiating significantly fewer plants per gram of callus when subcultured on a shoot differentiating medium. The isoline does, however, develop loci of meristematic cells when transferred from a medium containing 2,4-D to one containing benzyl adenine. After this transfer, plastids, mitochondria, dictyosomes, and endoplasmic reticulum appear to be more prevalent in many cells. Nuclei and nucleoli become more prominent in these cells. Ingrowths, lined with plasmalemma, develop along the outer tangential cell wall of many cells in contact with the culture medium and along various walls of cells found in the interior of the callus. These cells have characteristics of transfer cells. A few cells at the periphery of meristematic groups of cells elaborate lamellar structures similar to suberin lamellae in their cell walls.