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- Development and recovery of iron deficiency by iron resupply to roots or leaves of strawberry plantsPublication . Pestana, M.; Correia, P. J.; Saavedra, Teresa; Gama, Florinda; Abadía, Anunciación; Varennes, Amarilis deBare-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.
- Response of five citrus rootstocks to iron deficiencyPublication . Pestana, M.; Correia, P. J.; David, Maria Manuela; Abadía, Anunciación; Abadía, Javier; de Varennes, A.Citrus established in calcareous soils can be affected by iron (Fe) deficiency chlorosis which limits yield and the income of the farmer. The degree of the deficiency depends on the rootstock, but their tolerance to Fe chlorosis still requires further investigation. To study physiological parameters of citrus rootstocks that could be used to evaluate tolerance to Fe deficiency, plants of Troyer citrange (Citrus sinensis (L.) Osb. x Poncirus trifoliata (L.) Raf.), Carrizo citrange, Volkamer lemon (Citrus volkameriana Ten. & Pasq.), alemow (C. macrophylla Wester) and sour orange (C. aurantium L.) were grown in nutrient solutions with 0, 5, 10, 15 or 20 μM Fe. For each rootstock, plant height, root and shoot dry weights, and concentration of Fe in the shoots and roots were measured at the end of the experiment. Chlorophyll (CHL) concentration was estimated throughout the experimental period using a portable CHL meter (SPAD-502) calibrated for each rootstock. At the end of the experiment, CHL fluorescence parameters were measured in each rootstock with a portable fluorimeter. Maximal and variable fluorescence values indicated that the photochemistry of Troyer was more affected by a low concentration of Fe in the nutrient solution than other rootstocks. To compare rootstocks, the absolute CHL concentration was converted into relative yield by employing a scaling divisor based on the maximum value of total CHL in plants without Fe deficiency symptoms. Exponential models were developed to determine the minimum Fe concentration in nutrient solution required to maintain leaf CHL at 50% of the maximum CHL concentration (IC50). Models were also developed to assess the period of time the rootstocks were able to grow under Fe-stress conditions before they reached IC50. Volkamer lemon and sour orange needed the lowest Fe concentration (between 4 and 5 M Fe) to maintain IC50, and Troyer citrange had the highes! Fe requirement (14 M Fe). C. macrophylla and Carrizo citrange required 7 and 9 M of Fe, respectively. Similarly, Volkamer lemon and sour orange rootstocks withstood more days under total Fe depletion or with a low concentration of Fe (5 M Fe in nutrient solution) until they reached IC50, compared to the other rootstocks. The approach used led to a classification of the rootstocks into three categories, regarding their tolerance to Fe chlorosis: tolerant (sour orange and Volkamer lemon), with intermediate tolerance (C. macrophylla and Carrizo citrange), and with reduced tolerance (Troyer citrange).