IRON-DEFICIENCY STRESS INFLUENCES PHYSIOLOGY OF IRON ACQUISITION IN MARIGOLD (TAGETES-ERECTA L)

Excised roots of 'First Lady' marigold (Tagetes erecta L.) grown in an aerated 0 Fe nutrient solution hall Fe(III)DTPA reductase activity 14 -fold greater, and an enhanced ability to acidify the rhizosphere than plants grown in a solution containing 0.018 mM (1 ppm) Fe-DTPA. Reduc tase activity and rhizosphere acidification of plants grown in 0.018 a nd 0.09 mM Fe-DTPA were similar. Manganese concentration in leaves of plants grown in the 0 Fe treatment was 2-fold greater than in leaves o f plants grown in the 0.018 mM Fe-DTPA treatment. These results indica ted that 'First Lady' marigold is an Fe-efficient plant that possesses both an inducible or adaptive reductase system and the ability to aci dify the rhizosphere, and that these Fe-efficiency reactions do not oc cur when Fe is sufficient. Chemical name used: ferric diethylenetriami nepentaacetic acid, monosodium salt (Fe-DTPA).