DISTRIBUTION PATTERN OF ROOT-SUPPLIED (59)IRON IN IRON-SUFFICIENT ANDIRON-DEFICIENT BEAN-PLANTS

In order to study the iron (Fe) distribution pattern in bean plants wi th different Fe nutritional status, french bean (Phaseolus vulgaris L. ) seedlings were precultured in a complete nutrient solution with 8 x 10(-5) M FeEDTA for five days. Thereafter, plants were further supplie d with 8 x 10(-5) M FeEDTA (Fe-sufficient) or with only 2 x 10(-6) M F eEDTA (Fe-deficient) for another eight days. At this stage, the Fe-def icient plants had much lower chlorophyll contents and lower dry weight of the leaves but higher reducing capacity of the roots compared with the Fe-sufficient plants. For studies on short-term distribution of F e, the Fe-sufficient plants were supplied 8 x 10(-5) M (59)FeEDTA (spe cific activity 9.9 GBq/mol) and the Fe-deficient plants 1 x 10(-6) M ( 59)FeEDTA (specific activity 98.8 GBq/mol). The plants were harvested after 4 and 24 hours. Despite a much lower supply of (59)FeEDTA/(facto r 80), the Fe-deficient plants took up significantly more Fe-59 but tr anslocated less to the shoots (14.6% after 24 h) compared with the Fe- sufficient plants (29.4% after 24 h). However, regardless of the Fe nu tritional status of the plants, the majority of Fe-59 was translocated in the primary leaves. Our results demonstrate a similar distribution patterns of root-derived Fe-59 in the shoots of Fe-sufficient and Fe- deficient plants, and thus, no preferential direct translocation of Fe to the shoot apex in the Fe-deficient plants.