The Role of Gibberellins in Early Growth and Development of Sugar Beet

Abstract

Two gibberellin(GA)-like compounds were found in both roots and shoots of sugar beet plants using the barley endosperm bioassay. One had chromatographic properties similar to GA3 and GA1; the other was highly non-polar, relatively inactive in the endosperm assay, and may be a new gibberellin. Presence of the GA3/1-like compound was confirmed with the dwarf rice bio-assay. The quantity of this GA was relatively high in the root compared with the shoot at the 3–4 leaf stage when the first supernumerary cambia are being formed in the root. As plants developed through the 8–9 leaf stage and the 15–16 leaf stage the quantity of GA per unit fresh weight of material decreased. Application of gibberellic acid (GA3) to the roots of young sugar beet plants caused a significant increase in root dry weight shortly after treatment and the rate at which supernumerary cambia were produced was increased. Application of GA3 to a single petiole caused a significant increase in both root and shoot dry weight. GA3 applied to either root or shoot caused a reduction in the rate of leaf formation although total leaf area per plant and shoot dry weight were unaffected. The probable role of GA-like substances in controlling the growth and development of young sugar beet plants is discussed.