Seasonal Effects in the Hormonal Control of Growth in the Submerged Aquatic Macrophyte Ceratophyllum demersum

Abstract

AbstractThe season dependent changes in growth response to treatment with auxin or gibberellin were studied in the aquatic macrophyte Ceratophyllum demersum.Control plants show, under experimental conditions, a maximum growth in length in February. In the same period most of the lateral buds appear. Growth of the lateral buds occurs later.IAA causes a stimulation of growth in length from late November or December until February, in concentrations of 10−9M and 10−6M. There is almost no stimulation of lateral bud formation by IAA, only a slight increase from late November until December occurs by the lowest concentrations used. The highest concentration used, 10−4M, is in most cases supraoptimal for lateral bud formation; only when plants become dormant (August), this high dose may stimulate the process.GA3, in concentrations of 10−9, 10−6 or 10−4M, exhibits a dose dependent increase of the response with respect to growth in length and lateral bud formation. The response occurs earlier than that for IAA: already early in November, or December, until February.Growth of the lateral buds may show only a slight stimulation by IAA as well as GA in winter. From February until April all GA concentrations used could cause a small increase of the growth of sprouts. In the case of IAA, however, only the lowest concentration could cause a small increase.