Percorrer por autor "Varennes, Amarilis de"
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- Consequences of iron deficiency on fruit quality in citrus and stawberryPublication . Pestana, M.; Varennes, Amarilis de; Miguel, Maria Graça; Correia, P. J.; Nunes, CarlaIron deficiency (iron chlorosis) is an important nutritional disorder in several plants, including fruit trees and strawberry. Iron chlorosis does not result from a small level of iron in soils but rather from impaired acquisition and use of this metal by plants. Calcium carbonate, present in great amounts in calcareous soils, and the resulting large levels of bicarbonate ions, are the main causes of iron deficiency. Countries in southern Europe, such as Portugal, Spain, Italy and Greece, have large areas of calcareous soils with established orchards, where iron chlorosis is a major factor that limits yield and profit for the farmer. Iron chlorosis affects several metabolic processes and leads to nutrient imbalances in sensitive plants. Decreased yield and poor quality of fruit resulting from the iron deficiency justify the development of methods to diagnose and correct this disorder. No single approach has been found to solve iron chlorosis satisfactorily, making it one of the most complex nutritional deficiencies known. In this chapter we describe some aspects of the effects of iron availability on quality of strawberry and citrus fruit.
- 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.
- Effectiveness of different foliar iron applications to control iron chlorosis in orange trees grown on a calcareous soilPublication . Pestana, M.; Correia, P. J.; Varennes, Amarilis de; Abadía, Javier; Faria, E. A.The effectiveness on controlling Fe chlorosis in orange trees grown on calcareous soils was tested. The treatments were Fe(II) sulfate (500 mg Fe L ÿ1), sulfuric acid (0.5mM H2SO4), Fe(III)-chelate (Hampiron 654 GS, 120 mg Fe L ÿ1) and distilled water as a control. A non-ionic wetting agent was used in all treatments. The use of frequent foliar sprays alleviated Fe chlorosis in orange trees. Sprays of Fe(II) sulfate increased the concentrations of chlorophyll, Fe and zinc in leaves and improved fruit size and quality compared to fruits of control trees. Sprays of Fe(III)-chelate also increased leaf chlorophyll and Fe concentrations and improved fruit quality, but did not increase fruit size. Sprays of sulfuric acid alone slightly increased leaf chlorophyll and Fe concentrations, without improving fruit size and quality. These results suggest that foliar sprays with Fe could help to avoid yield and quality losses caused by Fe chlorosis in citrus orchards. Furthermore, these treatments could be done with relatively cheap materials such as solutions containing Fe(II) sulfate.
- Nutritional performance of Five Citrus rootstocks under different Fe levelsPublication . Pestana, Maribela; García-Caparrós, Pedro; Saavedra, Teresa; Gama, Florinda; Abadía, Javier; Varennes, Amarilis de; Correia, Pedro JoséIron is an essential micronutrient for citrus, playing an important role in photosynthesis and yield. The aim of this paper was to evaluate the tolerance to Fe deficiency of five citrus rootstocks: sour orange (S), Carrizo citrange (C), Citrus macrophylla (M), Troyer citrange (T), and Volkamer lemon (V). Plants were grown for 5 weeks in nutrient solution that contained the following Fe concentrations (in µM): 0, 5, 10, 15, and 20. At the end of the experiment, biomass (dry weight— DW), leaf area, total leaf chlorophyll (CHL), and the activity of root chelate reductase (FCR) were recorded. Additionally, the mineral composition of roots (R) and shoots (S) was evaluated. Principal component analysis was used to study the relationships between all parameters and, subsequently, the relations between rootstocks. In the first component, N-S, P-S, Ca-S, Cu-S, Zn-S, Mn-S, Zn-R, and Mn-R concentrations were related to leaf CHL and FCR. Increases in leaf CHL, Mg-R, and DW (shoots and roots) were inversely related to Cu-R, which was shown in the second component. The values obtained were consistent for V10, C15, and C20, but in contrast for S0 and S5. In conclusion, micronutrient homeostasis in roots and shoots of all rootstocks were affected by Fe stress conditions. The Fe/Cu ratio was significantly related to CHL, which may be used to assist rootstock performance.
- Quercetin promotes the recovery of iron chlorosis in strawberry plantsPublication . Pestana, Maribela; Saavedra, Teresa; Gama, Florinda; Rodrigues, Maria A.; Varennes, Amarilis de; Correia, Pedro José; Silva, José Paulo daIron (Fe) chlorosis is very common in plants cultivated in calcareous soils of the Mediterranean basin and is usually corrected by the application of Fe chelates to the soil, which can have a negative impact on the environment. The aim of this experiment was to assess the role of quercetin, a natural compound widely present in plants and known to bind Fe, in correcting Fe chlorosis when supplied in the Hoagland nutrient solution. In this context, strawberry plants were grown at different Fe concentrations, with 0 (Fe0), 1 (Fe1) and 5 (Fe5) mu M of Fe in the nutrient solution, until the onset of clear Fe chlorosis symptoms. Subsequently, the recovery of Fe chlorosis was investigated through the addition of Fe and/or quercetin (Q) to nutrient solutions. Throughout the experiment, leaf chlorophyll (Chl) was estimated using the SPAD values. The root ferric chelate-reductase (FCR) activity was determined in the root apices, and the foliar Fe concentration was also quantified. At the end of the experiment, plants grown without Fe but supplemented with Fe1 plus quercetin [Fe0+(Fe1+Q)] recovered completely from Fe chlorosis and showed a Chl concentration (700-800 mu mol m( 2)) in young leaves similar to that observed in control plants (Fe5). The remaining treatments exhibited lower Chl concentrations, with values ranging from 92.4 to 217.0 mu mol of Chl per m(2). FCR activity was approximately five-to six-fold higher in the Fe0+(Fe1+Q) treatment than in the Fe0 and Fe5 treatments. However, the plants that were consistently grown with Fe in the nutrient solution (Fe1 and Fe5) exhibited the highest Fe content in their leaves. The findings suggest that quercetin has the potential to function as an Fe complexing agent, thereby enhancing the recovery of strawberry plants with Fe deficiency.
- Relationships between nutrient composition of flowers and fruit quality in orange trees grown in calcareous soilPublication . Pestana, M.; Beja, Pedro; Correia, P. J.; Varennes, Amarilis de; Faria, E. A.A field experiment was conducted in a commercial orange orchard (Citrus sinensis (L.) Osb. cv. ‘Valencia late’ grafted on Citrange Troyer) established on a calcareous soil in the south of Portugal, to investigate if flower analysis could be used to predict fruit quality. In April 1996, during full bloom, flowers were collected from 20 trees. In March 1997 the fruits were harvested and their quality evaluated. This procedure was repeated every year during three years. Principal Component Analysis was used to evaluate the patterns of covariation in the concentrations of nutrients in flowers and in fruit quality parameters. Stepwise selection procedures wer then used to develop regression models relating fruit quality parameters to the mineral composition of flowers. The predictive power of the regression models was evaluated using an independent set of data. The mineral composition of flowers at full bloom could be used to predict quality parameters of fruit in the following year, namely fruit fresh weight and the maturation index. Magnesium, Ca and Zn registered in flowers were related to fruit fresh weight estimations and N, P, Mg and Fe were related to fruit maturation index. Reference values were determined for the mineral composition of flowers, corresponding to trees where fruits had a diameter > 76 mm.
- Root ferric chelate reductase is regulated by iron and copper in straberry plantsPublication . Pestana, M.; Correia, P. J.; Saavedra, Teresa; Gama, Florinda; Dandlen, S.; Nolasco, Gustavo; Varennes, Amarilis deIn the present experiment, we studied the interaction between copper (Cu) and iron (Fe) in strawberry plants grown in nutrient solutions containing different concentrations of Fe. Plants grown in the absence of iron (Fe0) had the characteristic symptoms of Fe deficiency, with smaller chlorotic leaves, less biomass, acidification of the nutrient solution, and roots that were smaller and less ramified, while no symptoms of Fe deficiency were observed in plants grown with Fe. A greater amount of Cu was found in roots of chlorotic plants than in those grown with Fe, while plants grown with 20M of Fe (Fe20) in the nutrient solution had a greater amount of Fe compared with plants from the other treatments. Chlorotic plants (Fe0) and plants grown with the greatest level of Fe (Fe20) had a greater root ferric chelate reductase (FC-R; EC 1.16.1.17) activity compared with the other treatments with 5 or 10M Fe in the nutrient solution. The same pattern was obtained for relative FC-R mRNA concentration and for the sum of Fe and Cu contents in shoots (leaves plus crowns). The DNA obtained from amplification of the FC-R mRNA was cloned and several of the inserts analysed by single strand confirmation polymorphism (SSCP). Although there were different SSCP patterns in the Fe20 treatment, all the inserts that were sequenced were very similar, excluding the hypothesis of more than one FC-R mRNA species being present. The results suggest that Cu as well as Fe is involved in FC-R expression and activity, although the mechanism involved in this regulation is unknown so far. Both small contents of Fe and Cu in plants led to an over-expression of the FC-R gene and enhanced FC-R activity in strawberry roots.
- The root ferric-chelate reductase of Ceratonia siliqua (L.) and Poncirus trifoliata (L.) Raf. responds differently to a low level of ironPublication . Pestana, M.; Gama, Florinda; Saavedra, Teresa; Varennes, Amarilis de; Correia, P. J.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 M Fe), with 1 M Fe, and with 10 M Fe (carob) or 40 M 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.