Abstract
Iron deficiency-induced chlorosis is one of the most damaging and widespread nutritional disorders in plants grown in Mediterranean-type soils. The aim of the present paper was to compare the effects of direct iron deficiency on two Medicago species from Tunisia: M. ciliaris and M. truncatula. Seedlings of both species were grown on a nutrient solution containing 30 mu M Fe (control) or 1 mu M Fe (iron deficiency treatment) for 30 days. We found that growth of both species was severely affected by direct iron deprivation. Nevertheless, M. truncatula experienced more marked decrease in biomass production and more severe chlorosis symptoms than M. ciliaris. The latter showed a better K and Fe distribution within the plant and a much higher Fe use efficiency for chlorophyll synthesis than the former. In addition, a capacity of root acidification due to a noticeable proton release rate was observed in M. ciliaris aiming to remobilize and take up Fe traces from the medium. Therefore, M ciliaris was more tolerant to the stress than M. truncatula.. This could explain the abundance and the better vigor of the former as compared to the latter in their alkaline natural biotope, Soliman sabkha.