Growth of the Embryo of Ginkgo Biloba Under Experimental Conditions. Iii. Growth Rates of Root and Shoot Upon Media Absorbed Through the Cotyledons

B all , E rnest . (North Carolina State Coll., Raleigh.) Growth of the embryo of Ginkgo biloba under experimental conditions. III. Growth rates of root and shoot upon media absorbed through the cotyledons. Amer. Jour. Bot. 46(2) : 130‐139. Illus. 1959.—Mature embryos of Ginkgo biloba were grown by inserting the cotyledons into agar medium containing one of the naturally‐occurring sugars of the seed. These sugars were utilized at 1, 2, 4, 8 or 16% (w/v). Root growth was best on the sugar‐mineral‐water media and occurred at its maximum in media containing 4% sugar (ca. 0.25 M). The sugars may be listed as follows in order of decreasing effectiveness in root growth: glucose, sucrose, levulose, raffinose, galactose. Since very different growth rates of roots occurred on media of the same osmotic values when the latter were determined by the various sugars, it is suggested that the root utilized the entire sugar molecule as a unit whether it was mono‐, di‐, or trisaccharide. Such media were not effective in supporting shoot growth. Outstanding growth of shoots was obtained when either glutamine or coconut milk was placed in the culture medium. It is concluded that root growth can occur at a substantial rate by utilizing sugar and manufacturing organic nitrogen from nitrates. Shoot growth, in contrast, appears to require sources of organic nitrogen such as may be furnished by glutamine or coconut milk. These phenomena are thought to constitute fundamental differences between the metabolism of root and shoot of this embryo. Mannitol caused severe inhibition of growth of both root and shoot. It is probably toxic to this embryo. Indoleacetic acid caused severe inhibitions of growth of both root and shoot at all except the lowest concentrations utilized.