[Further investigations on correlative bud inhibition]

By paper chromatographic analysis with isopropanol-water-ammonia two fractions which inhibit growth and germination and two fractions which promote straight growth but have no effect on germination were isolated from ether extracts of green pea shoots. The four fractions have the following properties:Rf 0.35; acid; promotes Avena straight growth; has no effect on germination of Lepidium;Rf 0.6; acid; inhibits straight growth and germination;Rf 0.75; acid; behaves like fraction Rf 0.35 but is less active;Rf 0.85; neutral or alkaline; acts similarly to fraction Rf 0.6.The activity of the two inhibiting fractions Rf 0.6 and 0.85 in inhibiting Avena straight growth and Lepidium germination is not changed when a neutral solvent (isopropanol-water) is used instead of the alkaline solvent isopropanol-water-ammonia.There is no evidence for an alkaline germination-inhibiting substance with a Rf-value of 0.55, the so-called correlation inhibitor reported by LIBBERT and LIEBENOW (1964).The behavior of the four fractions was investigated especially in two different bud growth tests. 1. Lateral buds from decapitated pea seedlings are prevented from outgrowth by application of lanolin pastes containing the two straight growth and germination inhibitors. The fraction Rf 0.6 is more active in this test than the fraction Rf 0.85. The inhibition is partly cancelled by the simultaneous addition of gibberellic acid. The fractions Rf 0.35 and 0.75 are inactive in this test. 2. In a second bud growth test isolated nodes with a single bud were used. These test organs are placed horizontally with the buds upward into aqueous solutions containing the chromatographic fractions. Bud growth is inhibited by fraction Rf 0.35 and (to a lesser extent) by fraction Rf 0.75; the fractions Rf 0.6 and 0.85 are inactive. The different action of these growth regulators in the described bud growth tests and their possible role in correlative bud inhibition in vivo is discussed.