EFFECT OF PRIMARY LEAVES ON FE-59 UPTAKE BY ROOTS AND FE-59 DISTRIBUTION IN THE SHOOT OF IRON SUFFICIENT AND IRON-DEFICIENT BEAN (PHASEOLUS-VULGARIS L) PLANTS

A study has been made on the effect of primary leaves on iron (Fe) dis tribution in the shoot. Bean (Phaseolus vulgaris L.) seedlings were pr ecultured in nutrient solution with 8x10(-5) M FeEDTA for 4 days, and then grown further with either 8x10(-5) M FeEDTA (+Fe) or without Fe s upply (-Fe) for another 5 days. Thereafter, both +Fe and -Fe plants we re treated in three different ways: undisturbed; one primary leaf remo ved; or one primary leaf shaded, starting two hours before supply (59) FeEDTA to the roots. The +Fe plants were supplied with 8x10(-5) M (59) FeEDTA, and the -Fe plants with only 1x10(-6) M (59)FeEDTA. After 1 to 8 hour uptake periods, plants were harvested and Fe-59 in different o rgans was determined. Removal or shading of one primary leaf did not a ffect Fe-59 uptake by roots and Fe-59 translocation to the shoot in +F e plants. In the -Fe plants, however, removal of one primary leaf decr eased Fe-59 uptake by roots, whereas shading of one primary leaf had n o effect on Fe-59 uptake but slightly enhanced Fe-59 translocation fro m roots to the shoot. The quantity of Fe-59 in primary leaves was posi tively correlated with quantity of Fe-59 in the stem in the -Fe plants , but not in the +Fe plants. In both, the +Fe and -Fe plants, the quan tity of Fe-59 in the shoot apex was positively correlated with Fe-59 i n primary leaves. The results suggest that irrespective of the Fe nutr itional status of plants, the source of Fe for the shoot apex is Fe re translocated from primary leaves.