MANGANESE INTERFERENCE IN THE ABSORPTION AND TRANSLOCATION OF RADIOACTIVE IRON (Fe) IN ANANAS COMOSUS (L.) MERR.

The interference of manganese with the availability of iron to pineapple plants has been explained by JOHNSON (7) and KELLEY (9, 10) as due to the oxidation of the latter by the former in soil and leaf tissues. Additional studies by SIDERIS, YOUNG and KRAUSS (14) and SIDERIs and YOUNG (17, 20) revealed that iron may be made unavailable in ample amounts to the leaf tissues after its precipitation in the exodermal root tissues at pH higher than 5.5, the latter resulting from the absorption by the roots of anions at higher rates than cations. All evidence obtained so far indicates that the iron requirements of pineapple leaves are small; also, differences in the iron content of chlorotic and green leaves are, likewise, small. Therefore, in order to avoid the unicertainty and difficulty of handling by ordinary chemical analyses the small amounts of iron absorbed by the roots at different periods and to eliminate the interference of preexisting amounts of this element in the tissues of the plants, the latter were grown in solution cultures supplied with iron containing a mixture of the radioactive isotopes Fe55 and Fe59, as well as the other stable isotopes as stated by the U. S. A. E. C. (28).