Figure 4.

Effect of ethylene precursors and inhibitors on the ferric reductase activity of Strategy I species. Ethylene (ACC) activates physiological responses, e.g., ferric reductase activity, to a lesser degree in plants grown with high levels of Fe than in plants grown with low levels. This suggests that ethylene acts in conjunction with some Fe-related repressive signals. On the other hand, ethylene inhibitors, like Co or AOA, block drastically the induction by Fe deficiency of this response, which suggests that ethylene is necessary for its activation. Data of ferric reductase activity expressed as percentage of –Fe plants (re-elaborated from Romera and Alcántara, 1994).