Iron deficiency interrupts energy transfer from a disconnected part of the antenna to the rest of Photosystem II |
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Authors: | Morales Fermín Moise Nicolae Quílez Rebeca Abadía Anunciación Abadía Javier Moya Ismael |
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Institution: | (1) Department of Plant Nutrition, Aula Dei Experimental Station, Consejo Superior de Investigaciones Científicas, Apartado 202, E-50080 Zaragoza, Spain;(2) Groupe Photosynthèse et Télédétéction, LURE/CNRS, Bat 203, Centre Universitaire Paris-Sud, B.P. 34, 91898 Orsay cedex, France;(3) Present address: Lasers Department, The National Institute for Lasers, Plasma and Radiation Physics, 76900 Bucharest-Magurele, Romania |
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Abstract: | Iron deficiency changed markedly the shape of the leaf chlorophyll fluorescence induction kinetics during a dark-light transition,
the so-called Kautsky effect. Changes in chlorophyll fluorescence lifetime and yield were observed, increasing largely the
minimal and the intermediate chlorophyll fluorescence levels, with a marked dip between the intermediate and the maximum levels
and loss of the secondary peak after the maximum. During the slow changes, the lifetime-yield relationship was found to be
linear and curvilinear (towards positive lifetime values) in control and Fe-deficient leaves, respectively. These results
suggested that part of the Photosystem II antenna in Fe-deficient leaves emits fluorescence with a long lifetime. In dark-adapted
Fe-deficient leaves, measurements in the picosecond-nanosecond time domain confirmed the presence of a 3.3-ns component, contributing
to 15% of the total fluorescence. Computer simulations revealed that upon illumination such contribution is also present and
remains constant, indicating that energy transfer is partially interrupted in Fe-deficient leaves. Photosystem II-enriched
membrane fractions containing different pigment-protein complexes were isolated from control and Fe-deficient leaves and characterized
spectrophotometrically. The photosynthetic pigment composition of the fractions was also determined. Data revealed the presence
of a novel pigment-protein complex induced by Fe deficiency and an enrichment of internal relative to peripheral antenna complexes.
The data suggest a partial disconnection between internal Photosystem II antenna complexes and the reaction center, which
could lead to an underestimation of the Photosystem II efficiency in dark-adapted, low chlorophyll Fe-deficient leaves, using
chlorophyll fluorescence.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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Keywords: | Chl fluorescence induction energy transfer iron deficiency phase fluorometry Photosystem II efficiency sugar beet time-resolved chlorophyll fluorescence |
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