Application of the split root technique to study iron uptake in cucumber plants.

The regulation exerted by the Fe status in the plant on Fe deficiency responses was investigated in Cucumis sativus L. roots at both biochemical and molecular levels. Besides the two activities strictly correlated with Fe deficiency response, those of the Fe(III)-chelate reductase and the high affinity Fe transporter, we considered also H(+)-ATPase (EC 3.6.3.6) and phosphoenolpyruvate carboxylase (EC 4.1.1.31), that have been shown to be involved in this response. Both enzymatic activities and gene expression were monitored using a split root system. Absence of Fe induced the expression of the four transcripts, accompanied by an increase in the corresponding enzymatic activities. The application of the split root technique gave some information about the regulation of Fe uptake. In fact, 24 h after split root application, transcripts were still high and comparable to those of the -Fe control in the Fe-supplied half side, while in the -Fe side there was a drop in the expression and the relative enzymatic activities. Major changes occurred after 48 and 72 h. The coordinated regulation of these responses is discussed.