Relative Activity of Gibberellins and their Derivatives on Barley

Abstract

GIBBERELLIC acid (gibberellin A₃) (I) is used extensively in the malting industry to accelerate the germination of barley (see Briggs¹ for review), but there seems to be no mention of the use of other gibberellins in this connexion. This communication reports the comparative behaviour of gibberellins A₁, A₃, A₄, A₅, A₇, A₈ and A₉ and of gibberellenic acid (II), allogibberic acid (III), gibberic acid (IV) and epiallogibberic acid (V), which are derivatives of A₃, on barley. The derivatives do not always show biological activity on plant tissues (see below). We find that gibberellenic acid (II) and allogibberic acid (III) stimulate the germination of barley as do all the gibberellins named above, whereas gibberic acid (IV) and epiallogibberic acid (V) do not. The germination tests² were carried out using 100 corns of dormant barley in a 9-cm Petri dish containing solutions (4 ml.) of the compounds named above (0.5 p.p.m.), and activity was based on the number of corns exhibiting visible signs of germination in 72 h. From the results of these tests the order of activity was found to be A₁ > A₇ > A₄ > A₃ > A₈ > gibberellenic acid > A₅ > allogibberic acid > A₉ > gibberic acid and epiallogibberic acid (inactive). No simple relationship was apparent between dose and response, but the order of activity was unchanged at higher (2 p.p.m.) and at lower (0.1 p.p.m.) dose rates than that stated above. The order of activity differs from that found by Brian, Hemming and Lowe³ for lettuce seedlings, and it now appears probable the seeds of different species respond differently to the various gibberellins.