Zinc Nutrition of Jarrah (Eucalyptus marginata Donn ex Smith) Seedlings

Abstract

The relationships of seven levels of zinc supply to dry matter and zinc concentration were assessed for jarrah (Eucalyptus marginata Donn ex Smith) seedlings grown for 84 days in a zinc-deficient sand in the glasshouse.

Zinc deficiency symptoms appeared within 28 days of sowing as a change in leaf colour of young leaves from green to bronze. Later, red areas developed and these became necrotic in severe cases. These symptoms were accompanied by decreased shoot and root dry weights.

Zinc concentrations in various plant parts were low and, with the exception of the shoot apex, showed little response to zinc supply. Concentrations at the shoot apex varied from 3µg/g in deficient plants to 12µg/g in plants with adequate zinc supply. We suggest that of the plant parts analysed, the shoot apex is the only one which may be useful in defining zinc status of jarrah seedlings. Critical zinc concentration for this tissue was between 10 and 12 µg/g dry matter.

Phosphorus concentrations in all plant parts, except the shoot apex, increased to very high levels with increasing zinc deficiency. It is suggested that some zinc deficiency symptoms of jarrah seedlings, e.g. necrosis, may have resulted from phosphorus accumulation due to zinc deficiency.