INHIBITING EFFECT OF AUTOCLAVED MALT PREVENTING THE IN VITRO GROWTH OF DATURA EMBRYOS

Abstract

STUDIES OF the necessary ingredients in nutrient solutions for the growth of excised plant embryos in artificial culture have been carried on for at least 40 years (Brink and Cooper, 1947; La Rue, 1936; White, 1931). Among other essential components has been an unknown embryo factor which has promoted the growth of immature embryos of Datura in vitro. Non-autoclaved coconut milk was the original source of this embryo factor (van Overbeek et al., 1942). Later Blakeslee and Satina (1944) reported a powdered malt extract solution, sterilized by Seitz filtration rather than by heat, as being an effective substitute for coconut milk. When the malt extract was sterilized by autoclaving, however, an inhibition of the growth of immature embryos was observed. In addition, Sanders (1947) observed that Seitz filtered malt interfered with the germination of Datura embryos, decreased root formation, and inhibited plumule growth. Heaton (1929) reported a substance obtained from malt which inhibited the multiplication of animal tissue cultured in vitro. Medawar, Robinson, and Robinson (1943) further described this inhibitory substance. The study reported in this paper is an attempt to throw still further light on the inhibiting effect of autoclaved malt extract. MATERIALS AND METHODS.-With the exception of the first experiment in which five species of Datura were used, the plant embryos were obtained from capsules resulting from the self-pollination of a single species of Datura, D. stramonium. The basic medium contained mineral salts and sucrose mixed according to a slightly modified form of the Randolph and Cox (1943) formula. The culture vials (12 X 50 mm.) containing 1.5 ml. of the basic medium were sterilized by autoclaving. With the exception of the autoclaved malt solution, all the test solutions were sterilized by Seitz filtration and subsequently added aseptically to the 1.5 ml. of the basic medium. The dissection technique involved removal of the seeds from the capsule, excision of the embryos from the seed, and immersion of the embryos into the sterile nutrient medium.