Photodegradation of FeDTPA in nutrient solutions. II. Effects on root physiology and foliar Fe and Mn levels in marigold

Marigold (Tagetes erecta L.) grown hydroponically in an irradiated nutrient solution containing FeDTPA had root ferric reductase activity 120% greater , foliar Fe level 33% less, and foliar Mn level 90% greater than did plants grown in an identical, nonirradiated solution, indicating that the plants growing in the irradiated solution were responding to Fe-deficiency stress with physiological reactions associated with Fe efficiency. The youngest le aves of plants grown in the irradiated solution had symptoms of Mn toxicity (interveinal chlorosis, shiny-bronze necrotic spots, and leaf deformation) . Plants grown in irradiated solution in which the precipitated Fe was repl aced with fresh Fe-chelate were, in general, no different from those grown in the nonirradiated solution. Chemical name used: ferric diethylenetriamin epentaacetic acid (FeDTPA).