Replacement of an Alternating Temperature Requirement for Germination by Gibberellic Acid

Abstract

IN many species of plants, seed-germination does not take place readily except under special conditions. A barrier to germination may be imposed by the seed coats or other coverings, by the presence of germination inhibitors in some part of the seed, by morphological or physiological immaturity of the embryo, by the need for light or for its absence, or by the need for alternating temperatures during germination¹. Chemical substances can in some cases substitute for specific environmental factors in effecting seed germination. Nitrates, for example, promote the germination of some light-requiring seeds in the dark¹, and the results of recent work indicate that the plant hormone gibberellic acid is particularly effective in overcoming several types of germination inhibition. In the germination of ‘Grand Rapids’ lettuce seeds, the primary light-requirement^2,3 and the light-requirement induced by high temperature or dark-osmotic treatments³ can be replaced by gibberellic acid. Gibberellic acid overcomes the inhibiting effect of coumarin on lettuce seed germination⁴ and of endogenous germination inhibitors present in Avena fatua⁵ and Betula spp.⁶ seeds. Kallio and Piiroinen⁷ found that gibberellic acid has a marked stimulating effect on the germination of seeds of 8 species, including Gentiana nivalis and Geranium sylvaticum; their experiments were conducted in the light at 24°.