EFFECTS OF IRON ON THE GROWTH AND ASH CONSTITUENTS OF ANANAS COMOSUS (L.) MERR

Abstract

Growth of A. comosus was approx. as good in minus- as in plus-iron soln. cultures supplied with ammonium-N salts, but with nitrate-N salts it was appreciably inferior in the minus-iron cultures. Average drift of pH during the 2-week intervals between renewal of the nutrient solns. was from pH 6.6 to 4.2 for the ammonium- and from pH 4.4 to 6.8 for the nitrate-N series. Rising pH values in the nitrate-N series caused some precipitation and decreased the amts. of available Fe. Fe was absorbed at exceedingly low rates from both N series and its precipitation on the roots was large. The amts. of iron translocated from roots to leaves were greater in the ammonium- than in the nitrate-series. Amts. of chlorophyll rather than of Fe constitute a better criterion for measuring the response of plants to Fe. P caused a slight precipitation of Fe on the roots. Some Mn was precipitated in the roots of the plus-iron cultures. The amts. of ash, particularly K, were greater on a % but not on a per plant basis in the tissues of the minus- than plus-iron cultures of the nitrate series. In the NH4 series the differences were small and in some cases the results were reversed.