No abstract

Bare root transplants of strawberry (Fragaria x ananassa Duch. cv. 'Selva') were transferred to nutrient solutions with or without iron (Fe). After six weeks of growth, plants in the solution without Fe were chlorotic and had morphological changes in roots typical of Fe deficiency. At this point, four treatments were imposed with three replicates (plants) each: plants always grown without sulphate every two days (Fe-leaves); chlorotic plants transferred to a solution with ferrous sulphate (Fe-solution). These plants were grown for nine days through which period chlorophyll (Chl) in leaves was estimated with a SPAD-502 apparatus. At the beginning and end of the experiment, root ferric chelate reductase (FC-R; EC 1.16.1.17) activity and the mineral composition of leaves and roots were measured. Six days after the addition of Fe to the solution (Fe-solution) leaves had Chl content similar to (Fe10). When Fe was applied to leaves (Fe-leaves), a slight regreening of new leaves was observed only at the end of the experiment. At this date, the FC-R activity remained the same in (Fe10) and increased even further in (Fe0). Plants in the Fe-solution treatment maintained an FC-R activity similar to the initial value in chlorotic plants, while the activity was drastically reduced in plants of treatment (Fe-leaves). The Fe concentration in leaves of (Fe0) and (Fe10) was similar, while application of Fe to leaves or nutrient solution resulted in an enhanced concentration of Fe in leaves. In contrast to what happened in Fe-solution, application of Fe to leaves did not lead to an increase in the concentration of Fe in roots. Root FC-R was correlated with the concentrations of Mn, Zn and Cu in leaves and with Cu in roots. Under our experimental conditions, FC-R activity in strawberry may be rapidly de-activated by pulses of Fe applied by foliar sprays. On the other hand, this de-activation mechanism is slower if Fe is applied directly to roots, suggesting a greater opportunity for plants to uptake more Fe. Please kindly consider the manuscript Recovery of iron deficiency by iron resupply to roots or leaves of strawberry plants for publication in Plant Physiology andBiochemistry. In this manuscript we present information involving the responses of Fedeficient plants resupplied with Fe, which may provide crucial information for the optimization of the Fe-fertilization strategies. The aims of the present study were to characterize the changes induced by Fe depletion on the chlorophyll content, root FC-R and mineral composition of roots and leaves and to compare two different ways to resupply Fe: by foliar or root fertilization. We also discuss the agronomical consequences of Fe resupply by fertilization. Cover Letter The FC-R activity was higher in chlorotic plants than in green plants. The concentrations of Cu, Mn and Zn in roots of chlorotic plants were higher than those presented by green plants. FC-R activity in strawberry may be rapidly de-activated by Fe applied by foliar sprays. The de-activation mechanism is s...

No abstract

Iron (Fe) deficiency is a common nutritional disorder in several crops grown in calcareous soils, but some species are well adapted to these conditions. A hydroponic experiment was conducted to compare the response of a calcicole species Ceratonia siliqua L. (carob) and of Poncirus trifoliata (L.) Raf., a citrus rootstock very sensitive to Fe deficiency. Rootstocks from both species were grown in nutrient solutions without Fe (0 µM Fe), with 1 µM Fe, and with 10 µM Fe (carob) or 40 µM Fe (P. trifoliata). A low level of Fe or its absence in the nutrient solution led to a significant decrease in P. trifoliata vegetative growth and in SPAD readings. The root activity of ferric-chelate reductase (FC-R), a key enzyme in Fe uptake, was low in the absence or with high levels of Fe. Its highest values were in roots exposed to a low level of Fe as described in several sensitive species. In contrast, the activity of FC-R was very high in carob in the absence of Fe and was decreased sharply even when only a low level of Fe was present in the nutrient solution. Plant growth and SPAD readings in the leaves of carob were similar in all treatments. Carob seems to maintain a large activity of root FC-R that may ensure enough Fe to satisfy plant demand. The fact that it presents a slow growing pattern may also contribute to the tolerance of this species to low levels of external Fe. o m Short communication The root ferric-chelate reductase of Ceratonia siliqua (L.) and Poncirus trifoliata (L.) Raf. responds differently to a low level of iron

To provide information towards optimization of strategies to treat Fe deficiency, experiments were conducted to study the responses of Fe-deficient plants to the resupply of Fe. Strawberry (Fragaria × ananassa Duch.) was used as model plant. Bare-root transplants of strawberry (cv. 'Diamante') were grown for 42 days in Hoagland's nutrient solutions without Fe (Fe0) and containing 10 μM of Fe as Fe-EDDHA (control, Fe10). For plants under Fe0 the total chlorophyll concentration of young leaves decreased progressively on time, showing the typical symptoms of iron chlorosis. After 35 days the Fe concentration was 6% of that observed for plants growing under Fe10. Half of plants growing under Fe0 were then Fe-resupplied by adding 10 μM of Fe to the Fe0 nutrient solution (FeR). Full Chlorophyll recovery of young leaves took place within 12 days. Root ferric chelate-reductase activity (FCR) and succinic and citric acid concentrations increased in FeR plants. Fe partition revealed that FeR plants expressively accumulated this nutrient in the crown and flowers. This observation can be due to a passive deactivation mechanism of the FCR activity, associated with continuous synthesis of succinic and citric acids at root level, and consequent greater uptake of Fe.