Short communication Development and recovery of iron deficiency by iron resupply to roots or leaves of strawberry plants Maribela Pestana a, * , Pedro José Correia a , Teresa Saavedra a , Florinda Gama a , Anunciación Abadía b , Amarilis de Varennes c a ICAAM, Universidade do Algarve, FCT, Ed. 8, Campus de Gambelas, 8005-139 Faro, Portugal b Department of Plant Nutrition, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), 50080 Zaragoza, Spain c Biosystems Engineering Center, Technical University of Lisbon, Tapada da Ajuda,1349-017 Lisbon, Portugal article info Article history: Received 3 October 2011 Accepted 3 January 2012 Available online 9 January 2012 Keywords: Chlorophyll Ferric chelate reductase Iron chlorosis Iron fertilization Nutrients abstract Bare-root transplants of strawberry (Fragaria ananassa Duch. cv. ‘Selva’) were transferred to nutrient solutions with or without iron (Fe). After six weeks of growth, plants grown in solution lacking Fe were chlorotic and showed morphological changes in roots typical of Fe deficiency. Subsequently, four treatments were applied for nine days: plants grown in continued absence of Fe (Fe0); plants grown in continued presence of 10 mM Fe (Fe10); foliar application of ferrous sulphate every two days to chlorotic plants (Fe-leaves); and growth of chlorotic plants in solution with ferrous sulphate (Fe-solution). After six days, the chlorophyll (Chl) content in leaves of Fe-solution plants was similar to that in Fe10 plants. Under the Fe-leaves treatment, a slight regreening of new leaves was observed only by the end of the experiment. After nine days, ferric chelate reductase (FC-R) activity was unchanged in Fe10 but increased in Fe0 plants. The FC-R activity of Fe-solution plants was similar to the initial value for chlorotic plants, whereas it was reduced drastically under the Fe-leaves treatment. The Fe concentration in leaves of Fe0 and Fe10 was similar, whereas the Fe-solution and Fe-leaves treatments enhanced leaf Fe concentration. In contrast to the Fe-solution treatment, foliar application of Fe did not increase the Fe concentration in roots. Under our experimental conditions, FC-R activity in strawberry appeared to be deactivated rapidly by pulses of Fe applied by foliar sprays. Deactivation was slower if Fe was applied directly to roots, which suggested that the plants had greater opportunity to take Fe. Ó 2012 Elsevier Masson SAS. All rights reserved. 1. Introduction Iron deficiency (iron chlorosis) is an important nutritional disorder in fruit trees that results from impaired acquisition and use of the metal by plants, rather than from a low level of Fe in soils. The most evident effect of Fe deficiency is a decreased content of photosynthetic pigments, which results in the relative enrichment of carotenoids over chlorophylls (Chl) and leads to the yellow colour that is characteristic of chlorotic leaves [1]. Plants employ mechanisms that promote Fe availability in the rhizosphere and plant. Dicot and monocot species, with the exception of members of the family Poaceae, have developed a strategy (Strategy I) that involves the induction of a ferric chelate reductase (FC-R; EC 1.16.1.17) in roots that converts Fe(III) toFe(II), which can then be taken up by an Fe(II) transporter [2,3]. Excretion of organic acids from roots to the rhizosphere can improve Fe availability further, and accumulation of these compounds in Fe- deficient plants can also stimulate long-distance transport of the metal [4]. Large concentrations of calcium carbonate, as in calcareous soils, result in high levels of bicarbonate ions, which are the main cause of Fe deficiency. Countries in southern Europe, such as Portugal, Spain, Italy, and Greece, have large areas of calcareous soils that contain established orchards. In these orchards, Fe chlorosis is a major factor that limits growth, yield, and profitability [5e7]. Crops that are commonly affected by Fe deficiency when grown in calcareous soils include apple, blueberry, cherry, citrus, corn, grape, turf and pasture grasses, peach, pear, plum, quince, sorghum, soybean, and strawberry [5e10]. When grown on calcareous soils, strawberry production may be affected seriously by induced Fe deficiency. Strawberry shows wide genotypic variation in tolerance Abbreviations: BPDS, Fe(II)ebathophenantrolinedisulfonate; Chl, chlorophyll; DW, dry weight; EC, electrical conductivity; EDDHA, ethylenediamine-N-N’bis(o- hydroxyphenylacetic) acid; EDTA, ethylenediamine-tetraacetic acid; FC-R, ferric chelate reductase; FW, fresh weight; MES, 2-(N-morpholino)ethanesulfonic acid; SPAD, soil and plant analyser development. * Corresponding author. Tel.: þ351289800900; fax: þ351289818419. E-mail address: fpestana@ualg.pt (M. Pestana). Contents lists available at SciVerse ScienceDirect Plant Physiology and Biochemistry journal homepage: www.elsevier.com/locate/plaphy 0981-9428/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.plaphy.2012.01.001 Plant Physiology and Biochemistry 53 (2012) 1e5