PLANT PHYSIOLOGY , Vol 107, Issue 4 1195-1199, Copyright © 1995 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Metabolic Implications in the Biochemical Responses to Iron Deficiency in Cucumber (Cucumis sativus L.) Roots
G. Rabotti, P. De Nisi and G. Zocchi
Dipartimento Fisiologia Piante Coltivate e Chimica Agraria, University of Milan, Via Celoria 2,I-20133 Milano, Italy
Strategy I plants respond to Fe deficiency by inducing morphological and
biochemical modifications at the root level that are apt to make iron
available for uptake. Cucumber (Cucumis sativus L.) grown in the absence of
Fe has been shown to increase the capacity to acidify the rhizosphere and
Fe3+ reduction activity. We have determined in these roots some metabolic
activities that might be correlated with the increased proton extrusion.
Proton efflux from roots may be followed by a mechanism regulating the
cytosolic pH according to the pH-stat theory. Roots grown in the absence of
Fe showed an increase in dark 14CO2 fixation and organic acid synthesis and
a 6-fold increase in the extractable phosphoenolpyruvate carboxylase
activity with respect to the control roots. Dehydrogenase activities
producing cytosolic NAD(P)H were also increased under Fe deficiency. The
presence of Fe2+, but not Fe3+, inhibited dark 14CO2 fixation in a range
between 24 and 52% but did not show any effect on the in vitro
phosphoenolpyruvate carboxylase activity.
