Physiological Aspects of Time of Application of Copper to Wheat Plants

Abstract

Time of application of Cu as soil dressing or foliar spray had large effects on grain yield of wheat plants grown in Cu-deficient soil in the glasshouse. Times of application of Cu (4 mg per pot in one dose) ranged from sowing to maturity in weekly intervals. The soil dressing of Cu produced excellent grain yield if applied any time from sowing to early boot stage. Little or no grain formed on any tillers which had passed this critical early boot stage at the time of application; the pollen produced by these tillers was non-viable, anthers were not exserted, and maturation was delayed. These results suggest that microsporogenesis was interrupted by Cu deficiency at or near meiosis. Tillering was the optimum time for foliar application of Cu (CuSO₄ + Ca(0H)₂ in suspension); early or late applications failed to produce grain. However, this form of Cu proved unsatisfactory for foliar application under glasshouse conditions, possibly owing to the absence of rain or dew.