Modification of Root-Shoot-Ratio of Sunflower (Helianthus annuus,L.) by Nitrogen Supply and a Triazole-Type Plant Growth Regulator

A factorial nutrient solution experiment with 3 N levels and 4 plant growth regulator (PGR) rates with sunflower (Helianthus annuus, L., cv. Sorex) was conducted to investigate the effect of both variables on shoot and root development. Nitrogen shortage resulted in reduced shoot and root growth throughout the experiment, but root growth was less affected than the shoot PGR treatments drastically reduced shoot biomass production. Root growth was promoted. Both reduced nitrogen supply and application of a triazole plant growth regulator (BAS 111. W) increased the proportion of roots relative to the shoot.