THE EFFECTS OF THE FORM OF NITROGEN AND THE AMOUNT OF BASE SUPPLY ON THE ORGANIC ACIDS OF TUNG LEAVES

Abstract

The effects of base supply (Ca, K, Mg) and N source (nitrate vs. ammonium) on total organic acid and oxalic acid production were investigated with seedling tung trees grown in a nutritional expt. set up in factorial design. Oxalic acid formation was found to be directly related to nitrate concn. and N uptake from all nitrate solns. as well as to Ca supply and uptake. Both K and Mg influenced oxalic acid formation by their repressing effect on Ca uptake. It is suggested that oxalic acid formation in the tung plant is a by-product of the process of oxidation of carbohydrates which furnish energy for reduction of nitrate to protein N. With an all-nitrate supply, a high Ca requirement results from the precipitation of oxalate with the oxalic acid formed in this type of N metabolism. When nitrate reduction is lessened, a correspondingly lower Ca requirement exists for normal growth.