In vitro germination and seedling development of Dalzellia zeylanica (Gardner) Wight (Podostemaceae)

Abstract

Seeds were germinated aseptically on thermocole cubes in 1/5 strength Murashige and Skoog's (1962) liquid medium (MS). The mature embryo has two well-developed cotyledons but lacks a plumule and a distinct radicle. The embryo emerges from the seed by the elongation of cotyledons and hypocotyl. The epidermal cells at the radicular pole elongate to form rhizoids. Proliferation of cells of the plumular pole gives rise to six to eight leaf primordia. An endogenously formed protuberance in the hypocotyledonary region develops into a green, dorsiventral thallus. The margins of the thallus also bear leaves. The presence of a band of small meristematic cells (five or six layers thick) below the apical mantle of large irregular cells has been seen in paradermal sections of thallus tips. Presumably they participate in the growth of the thallus. A vertical section of the thallus shows parenchymatous ground tissue and a strand of vascular tissue in the middle of the thallus which divides to supply the branches of the thallus. Tracheary elements have spiral/annular thickenings. Sieve elements showed callose when stained with aniline blue and viewed under a fluorescence microscope.