THE RESPONSE OF SEEDLINGS OF 2 DIPTEROCARP SPECIES TO NUTRIENT ADDITIONS AND ECTOMYCORRHIZAL INFECTION

An experiment was conducted to investigate the effect of ectomycorrhiz al infection on growth and nutrient uptake, especially of P and K of d ipterocarp seedlings. Hopea helferi (Dyer) Blanco and Hopea odorata Ro xb. seedlings were grown in a sandy loam soil given a basal dressing. Nutrient treatments were unamended soil (NIL), amended soil with the a ddition of P and K (F), amended soil without P but with K (-P), amende d soil without K but with P (-K), amended soil without P or K addition (-PK). Seedlings grown in the amended soil treatments showed foliar s ymptoms suggestive of calcium deficiency. Ectomycorrhizal infection ap peared to improve shoot Ca concentration and relieved the foliar sympt oms. Ectomycorrhizal infection in H. odorata plants increased shoot P concentration and increased shoot and total dry weight to the same or greater extent than those of uninfected plants growing on P amended so il. H. helferi showed a positive response to ectomycorrhizal infection in shoot, root and total dry weight in all nutrient treatments but no response to the nutrient treatments themselves.