Role of sulphur conferring differential tolerance to iron deficiency in Pisum sativum

This study investigated the effects of sulphur foliar spray and S deprivation on Fe deficiency responses in two contrasting pea genotypes, Santi (tolerant) and Parafield (sensitive). Foliar application of sulphur enhanced morphological growth features, leaf chlorophyll score and root Fe chelate reductase activity predominantly in Santi and to a lesser extent in Parafield. These capacities eventually contribute to the higher Fe deficiency tolerance in Santi. These results are also important in terms of ameliorating Fe deficiency effects in peas through S foliar spray. Further, targeted investigation was performed on S deprivation in Santi and Parafield. S deprivation caused severe stunting, chlorosis and wrinkling in leaves and caused decrease in leaf Fe concentrations both in Santi and Parafield under Fe deficiency. S deprivation also led to a significant decrease in Fe chelate reductase and proton extrusion activities in both genotypes in Fe shortage. We conclude that S deficiency exacerbates Fe deficiency in peas by preventing the induction of the Fe chelate reductase activity and proton extrusion in roots. Taken together, these data confirm that Fe deficiency symptom expression and the Fe deficiency responses in peas are largely determined by S nutritional status.