Abstract: | Two gibberellin(GA)-like compounds were found in both rootsand shoots of sugar beet plants using the barley endosperm bioassay.One had chromatographic properties similar to GA3 and GA1; theother was highly non-polar, relatively inactive in the endospermassay, and may be a new gibberellin. Presence of the GA3/1-likecompound was confirmed with the dwarf rice bio-assay. The quantityof this GA was relatively high in the root compared with theshoot at the 34 leaf stage when the first supernumerarycambia are being formed in the root. As plants developed throughthe 89 leaf stage and the 1516 leaf stage thequantity of GA per unit fresh weight of material decreased. Application of gibberellic acid (GA3) to the roots of youngsugar beet plants caused a significant increase in root dryweight shortly after treatment and the rate at which supernumerarycambia were produced was increased. Application of GA3 to asingle petiole caused a significant increase in both root andshoot dry weight. GA3 applied to either root or shoot causeda reduction in the rate of leaf formation although total leafarea per plant and shoot dry weight were unaffected. The probablerole of GA-like substances in controlling the growth and developmentof young sugar beet plants is discussed. |