Plant Physiol, February 2000, Vol. 122, pp. 337-344
Iron Deficiency Decreases the Fe(III)-Chelate Reducing Activity
of Leaf Protoplasts1
Elena B.
González-Vallejo,2
Fermín
Morales,2
Luis
Cistué,
Anunciación
Abadía, and
Javier
Abadía*
Departments of Plant Nutrition (E.B.G.-V., F.M., A.A., J.A.) and
Genetics and Plant Production (L.C.), Aula Dei Experimental Station,
Consejo Superior de Investigaciones Científicas, Apartado 202, E-50080 Zaragoza, Spain.
The
ferric-chelate reductase (FC-R) activity of mesophyll protoplasts
isolated from Fe-sufficient (control) and Fe-deficient sugar beet
(Beta vulgaris L.) leaves has been characterized.
Measurements were made in an ionic environment similar to that in the
apoplastic space of the sugar beet mesophyll cells. The FC-R activity
of Fe-sufficient and Fe-deficient protoplasts was dependent on light. Fe deficiency decreased markedly the FC-R activity per protoplast surface unit. The optimal pH for the activity of the FC-R in mesophyll protoplasts was in the range 5.5 to 6.0, typical of the apoplastic space. Beyond pH 6.0, the activity of the FC-R in mesophyll protoplasts decreased markedly in both Fe-sufficient and Fe-deficient protoplasts. These data suggest that both the intrinsic decrease in FC-R activity per protoplast surface and a possible shift in the pH of the apoplastic space could lead to the accumulation of physiologically inactive Fe
pools in chlorotic leaves.
1
This work was supported by the Comisión
Interministerial de Ciencia y Tecnología (grant no. AGR97-1177
to A.A.), the Dirección General de Enseñanza Superior e
Investigación Científica (grant no. PB97-1176 to J.A.),
and the Commision of European Communities (grant no. AIR3-CT94-1973
to J.A.). F.M. and E.B.G.-V. were recipients of a contract and a
predoctoral fellowship from the Spanish Ministry of Education and
Culture, respectively.
2
These authors contributed equally to the paper.
*
Corresponding author; e-mail jabadia{at}eead.csic.es; fax
34-976-575620.
© 2000 American Society of Plant Physiologists
