Anomalous Water Relations in Copper-Deficient Wheat Plants

Abstract

Leaf water potential, diffusive resistance, relative water content, weekly water use, yields and head bending were measured on wheat plants subjected to four copper levels (0, 0.4, 0.8 or 4.0 mg Cu per pot) and two water levels (6 or 12% soil water content). Severe copper deficiency (Cu 0) resulted in no grain yield, wilting, increased leaf diffusive resistance and, at the same time, increased leaf water potential relative to plants receiving 4.0 mg Cu (Cu 4.0). Water supply effects were observed but there was no interaction between copper and water treatments. Mild copper deficiency (Cu 0.4, Cu 0.8) resulted in small yield decreases, relative to Cu 4.0, and increased head bending towards maturity. It is concluded that wilting, characteristic of copper-deficient plants, is due to structural weakness (decreased lignification) and not to the water status of the plants; also, increased leaf diffusive resistance is due to a specific effect of copper deficiency on guard cells and not to decreased leaf water potential.