GROWTH AND NUTRITION OF HYBRID POPLAR IN RESPONSE TO PHOSPHORUS, ZINC, AND GIBBERELLIC-ACID TREATMENTS

Phosphorus-induced growth inhibition in poplar hybrid shoots in a greenhouse trial was corrected by treatment with either soil-incorporated Zn fertilizer or leaf spray of gibberellic acid (GA). Increasing P applications depressed plant growth. Zinc added alone failed to stimulate growth, but when combined Zn with P it increased total biomass production by 27-41%. GA spray increased height and dry weight of shoot by 32% and 11%, respectively, at the expense of root growth without increasing total biomass. Foliar P and Zn concentrations were unchanged by GA treatment, but N concentrations were reduced, probably because of dilution. Although GA may be useful for stimulating shoot elongation, it may not be practical for correcting P-induced Zn disorders in hybrid poplar culture.