9i. Saccharase Activity in the Barley Plant

IT has long been recognized that most plant tissues have the capacity of inverting sucrose, but intensive study of saccharase action has hitherto been almost exclusively concerned with the saccharase of yeast [O'Sullivan & Tompson, 1890; Hudson, 1908, 1, 2; Michaeis & Menten, 1913; Nelson & Hitchcock, 1921; von Euler & Josephson, 1923; Willstatter & Kuhn, 1923; Weidenhagen, 1930, and many other papers by these authors and their collaborators]. The information regarding the saccharase of higher plants is frequently confined to records of its presence and of the optimum pH for its action [Kastle & Clark, 1903; Bailey, 1912; Colin, 1915; Maestrini, 1921; McGuire & Falk, 1920; Traegel, 1923; Kondo et al. 1929; Astruc & Mousseron, 1927; Blagoveschenski & Sossiedov, 1925; Matsusima, 1937]. Some attention has been paid to possible differences in the course of sucrose hydrolysis by saccharases from different plants [McGuire & Falk, 1923] and the effect of nutrient ions, particularly potassium, has been studied by Doby & Hibbard [1926; 1927], Harrt [1929] and Cattle [1933], while Vinson [1908] and Emiliani [1938] record variations of activity with age in the date and vine respectively. Finally a group of Russian workers [Arassimovitsch, 1939; Kursanov, 1936, 1, 2; Kursanov & Kriukova, 1937, 1, 2; Oparin, 1937, 1,2; Rubin, 1936; Sisakyan, 1937] have quite recently investigated problems of saccharase action by infiltration methods. The present paper records the changes in saccharase activity of the organs of the barley plant during the later half of the vegetative stage of growth and throughout the phases of stem elongation and ear development. The purpose of the investigation, which forms part of a study of the physiology of the barley plant in progress in this laboratory, was to ascertain whether the potential saccharase activity, as measured by the action of killed tissue on sucrose, could in any circumstances be a limiting factor in the interconversion of the sugars. It may be stated at once that no such evidence was found. Potential activity was always far in excess of all possible requirements, and the experiments merely emphasize the complexity of the problems involved in the mechanism of saccharase action. Nevertheless the results form a fairly complete record of the changes occurring in the barley plant with age, and for this reason it has been considered worth while to publish them. The preliminary work necessary to ascertain appropriate conditions for making comparisons of activities at different times is first discussed.