Description
Iron (Fe) is abundant in soils and although it is required in small amounts by
plants the incidence of iron chlorosis (Fe deficiency) is very common in a number of
crops and requires massive soil application of Fe-chelates to correct it. In this work, we
present the most important results obtained in several experiments conducted with
strawberry to study the physiological and biochemical response mechanisms to Fe
deficiency, and the assessment of novel alternatives to control this nutritional disorder.
In all experiments, conducted in hydroponic systems, symptoms were induced
by withdrawing Fe from the solution and the results were compared to a control
treatment grown with Fe. The degree of chlorosis and symptoms recovery was
estimated using SPAD values. The activity of iron chelate reductase, the enzyme
responsible for Fe reduction in roots, was determined in root apices by colorimetric
quantification of the BPDS complex. The Fe concentration in leaves and roots was
quantified by atomic absorption spectrophotometry after treatments at 450 ºC and acid
digestion of the ashes obtained.
Strawberry plants that grew always without Fe, presented Fe chlorosis and
morphological external root modifications associated with increases of the activity of
the Fe-reductase enzyme. The recovery of chlorotic plants was achieved by application
of Fe sulphate either to leaves or to the nutrient solution. In plants recovered by using
Fe in the solution, the enzyme maintained a large activity, suggesting a strategy to
increase plant Fe pools.
As an alternative to synthetic Fe chelates, we also tested a foliar application of a
plant extract obtained from fresh grass clippings (national patent PT/103584-2009 of
UALG, and international patent PCT/PT2007/000041-2008, UALG and ADPFertilizantes),
which was effective in chlorosis recovery after three applications. The
results are discussed in order to highlight the practical implications of these responses
under a perspective of optimization of crop Fe fertilization
; Gama, Florinda 
