Growth of sugar-beet crops including the influence of synthetic plant growth regulators

Abstract

SummaryObservations are presented from a crop of sugar beet grown in Cambridgeshire during 1978, and a field trial at Sutton Bonington during 1985 in which the influence of synthetic plant growth regulators (PGRs) daminozide, chlormequat, GA4+7and ethephon were compared.Several distinct patterns of growth were evident, being similar for both growing seasons and described by two intersecting straight lines. Early development was characterized by a slow rate of biomass accumulation, a dominance of foliage production with a constant but small root fraction (around 40%), a low specific leaf area and a slow but conservative rate of sucrose fractionation. Later in the season the rate of stand growth was both constant and maximal, the root fraction doubled, specific leaf area increased and the rate of sucrose accumulation rose markedly.Transitions between developmental phases occurred at various times dependent on variate under consideration. The onset of the main growth period began at the end of June, followed by an increase in the rate of sucrose accumulation about 2 weeks later. Finally, near the end of July, partition of assimilate into the root assumed a faster rate. Changes in the partitioning into both roots and sucrose are discussed in relation to the development of the secondary cambium.Generally there were no effects of PGRs on biomass accumulation, dry-matter partitioning, specific leaf area and sucrose accumulation. However, daminozide increased early canopy expansion and early dry-matter production but failed to influence biomass or sugar yield.