Effects of Nitrogen on the Nitrogenous Fractions of Ananas comosus (L.) Merr.

Abstract

The effects of high vs. low N (140 vs. 2.8 mg. per liter of nutrient soln.), supplied either as NO3-, or NH4+, caused changes in the amts. of the various nitrogenous fractions of the tissues of 1-yr.-old A. comosus. The plants of the high-N cultures absorbed approx. 5 times more N than of the low-N cultures, although the N content of the nutrient solns. was 50 times greater for the former cultures. Total-N and protein-N were from 3-4 times, and soluble-N was from 4-8 times greater in the high-N cultures. Soluble organic-N was higher in the chlorophyllous than non-chlorophyllous regions of the leaves. Soluble organic-N fractions such as amide, mono-amino and basic were higher in the ammonium than nitrate series. Leaf protein-N was higher in the terminal chlorophyllous than in the basal non-chlorophyllous regions of the leaves. Protein-N correlated with few exceptions to mono-amino-N and basic-N. The results suggest a continuous formation of amino N from proteins undergoing normal hydrolysis in the cell or synthesis of proteins by condensation of amino acids in cultures supplied with either adequate or subadequate supplies of inorganic N. Excessive supplies of inorganic N either as NH4+ or NO3- may cause accumulations of soluble organic-N fractions produced by enzymatic synthesis from ammonia with carboxylic acids and similar to those presumably released from protein breakdown.