Abscisic Acid and Morphogenesis in Lemna polyrhiza L.

Abstract

THE plant hormone abscisic acid has been shown to promote abscission and dormancy, to inhibit cell elongation and to be involved in several hormone mediated plant responses^1,2. The action of this hormone may involve the inhibition of specific mRNA synthesis³ or more generally the inhibition of DNA synthesis⁴. The results reported here describe the striking effects of abscisic acid on the growth and morphogenesis of Lemna polyrhiza. The offshoot primordia of this species usually develop as vegetative fronds, but in some conditions the ontogenetic growth pattern is modified in such a way that specialized resting fronds, turions, are produced. These are morphologically and physiologically quite different from the normal vegetative fronds, and are important in enabling the plant to overwinter in a dormant state⁵. Turion formation has been suggested to occur in environmental conditions which maintain the photosynthetic rate above that necessary to sustain growth and respiration^5,6.