Maize Endosperm Tissue Grown In vitro. I. Culture Requirements

IN RECENT YEARS the number of plant tissue cultures grown in vitro has been greatly increased.Other than the usual callus cultures derived from dicotyledonous plants (Gautheret, 1947a), tissues derived from monocotyledonous plants as well as from the Pinaceae, Ginkgoaceae, Filicinae, and the Lycopodinae have been established in culture.Curtis and Nichol (1947), obtained cultures of overgrowths produced by orchid embryos grown in vitro.Morel and Wetmore (1951a) were successful in growing callus tissues derived from the tubers of several tropical members of the Araceae.Ball (1950, 1953) has described the regeneration of new plants from Sequoia callus as well as the absorption of radioactive isotopes by these same cultures.Lowenberg and Skoog (1952) reported on their success in growing the callus produced by two species of Pinus embryos.Reports of several tissues derived from unusual morphological sources have also appeared recently in the literature.Thus, the endosperm of maize was first isolated by LaRue as a continuous culture in 1949.Morel and Wetmore (1951b) have grown Osmunda gametophyte callus in vitro.Wetmore and Morel (1951a, 1951b) have established tissue cultures derived from the gametophyte of Lycopodium and the female gametophyte of Selaginella.The endosperm of Asimina triloba has been isolated by Lampton (1952) as a continuous tissue culture.Tulecke (1953) reported on the growth of a tissue which arose in in vitro cultures of Ginkgo pollen.This tissue appears to be the most unusual of all plant tissue cultures as it may represent an extended growth of the greatly reduced male gametophyte since the tissue appears to have arisen from the tube cell.Recently LaRue (unpublished) and his students have grown endosperm of Lolium perenne and stem tissues of Cryptomeria japonica, Cupressus [unebris, Theobroma cacao and Citrus aurantium as well as tobacco-root tumor tissue.None of the tissues mentioned in the above paragraph except for Osmunda gametophyte callus and newly cultured maize endosperm have been reported to differentiate any vascular elements or the more 1