ETHYLENE INVOLVEMENT IN THE OVER-EXPRESSION OF FE(III)-CHELATE REDUCTASE BY ROOTS OF E107 PEA [PISUM-SATIVUM L (BRZ, BRZ)] AND CHLORANERVA TOMATO (LYCOPERSICON-ESCULENTUM L) MUTANT GENOTYPES

Recently, ethylene was reported to be involved in the regulation of Fe (III)-chelate reducing capacity by cucumber (Cucumis sativus L.) roots , Here, we studied the effect of two ethylene inhibitors, aminooxyacet ic acid (AOA) and cobalt, on the Fe(III) reducing capacity in roots of mutant genotypes [E107 pea [Pisum sativum L. (brz, brz)] and chlorone rra tomato (Lycopersicon esculentum L.] that exhibit high rates of Fe( III)-chelate reduction and excessive iron accumulation, The ethylene i nhibitors, AOA and cobalt, markedly inhibited Fe(III)-chelate reducing capacity in roots of both genotypes, Over-expression of root Fe(III) reductase activity by both mutants appears to be related to ethylene, Possibly, both mutants are genetically defective in their ability to r egulate root ethylene production, The large inhibitory effect of both ethylene inhibitors on Fe(III)-chelate reducing capacity in roots of t he mutant tomato genotype, chloronerva, disputes the contention that t he nicotianamine-Fe(II) complex is the repressior of the gene responsi ble for Fe(III)-chelate reductase activity, as previously suggested by others. However, since nicotianamine shares the same biosynthetic pre cursor as ethylene, i.e. S-adenosyl methionine, nicotianamine may affe ct Fe(III)-chelate reductase activity in dicot and non-grass monocot r oots by influencing ethylene biosynthesis.