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- Effects of foliar application of organic acids on strawberry plantsPublication . Saavedra, Teresa; Gama, Florinda; Rodrigues, Maria Joao; Abadía, Javier; de Varennes, Amarilis; Pestana, Maribela; Da Silva, José Paulo; Correia, Pedro JoséThe large economic costs and environmental impacts of iron-chelate treatments has led to the search for alter-native methods and compounds to control iron (Fe) deficiency chlorosis. Strawberry plants (Fragaria x ananassa) were grown in Hoagland's nutrient solution in a greenhouse with two levels of Fe: 0 and 10 mu M Fe(III)-EDDHA. After 20 days, plants growing without Fe showed typical symptoms of Fe deficiency chlorosis in young leaves. Then, the adaxial and abaxial sides of one mature or one young leaf in each plant were brushed with 10 mM malic (MA), citric (CA) or succinic (SA) acids. Eight applications were done over a two-week period. At the end of the experiment, the newly emerged (therefore untreated), young and mature leaves were sampled for nutritional and metabolomic analysis, to assess the effectiveness of treatments. Leaf regreening was monitored using a SPAD-502 apparatus, and the activity of the ferric chelate-reductase activity (FCR) was measured using root tips. Iron deficiency negatively affected biomass and leaf chlorophyll but did not increase FCR activity. Application of succinic acid alleviated the decrease in chlorophyll observed in other treatments, and the overall nutritional balance in the plant was also changed. The concentrations of two quinic acid derivatives increased under Fe deficiency and decreased in plants treated with succinic acid, and thus they are proposed as Fe stress markers. Data suggest that foliage treatments with carboxylates may be, in some cases, environmentally friendly alter-natives to Fe(III)-chelates. The importance of Fe mobilization pathways in the formulation of new fertilizers is also discussed.
- Nutritional and functional evaluation of inula crithmoides and mesembryanthemum nodiflorum grown in different salinities for human consumptionPublication . Ribeiro Lima, Alexandre; Gama, Florinda; Castañeda-Loaiza, Viana; Costa, Camila; Schueler, Lisa M.; Santos, Tamara; Salazar, Miguel; Nunes, Carla; Cruz, Rui M. S.; Varela, J.; Barreira, LuísaThe nutritional composition and productivity of halophytes is strongly related to the biotic/abiotic stress to which these extremophile salt tolerant plants are subjected during their cultivation cycle. In this study, two commercial halophyte species (Inula crithmoides and Mesembryanthemum nodiflorum) were cultivated at six levels of salinity using a soilless cultivation system. In this way, it was possible to understand the response mechanisms of these halophytes to salt stress. The relative productivity decreased from the salinities of 110 and 200 mmol L−1 upwards for I. crithmoides and M. nodiflorum, respectively. Nonetheless, the nutritional profile for human consumption remained balanced. In general, I. crithmoides vitamin (B1 and B6) contents were significantly higher than those of M. nodiflorum. For both species, β-carotene and lutein were induced by salinity, possibly as a response to oxidative stress. Phenolic compounds were more abundant in plants cultivated at lower salinities, while the antioxidant activity increased as a response to salt stress. Sensory characteristics were evaluated by a panel of culinary chefs showing a preference for plants grown at the salt concentration of 350 mmol L−1. In summary, salinity stress was effective in boosting important nutritional components in these species, and the soilless system promotes the sustainable and safe production of halophyte plants for human consumption.
- Relationship between tipburn and leaf mineral composition in strawberryPublication . Palencia, P.; Martinez, F.; Ribeiro, E.; Correia, Maribela Pestana; Gama, Florinda; Saavedra, Teresa; de Varennes, A.; Correia, P. J.Malformation of emerging leaves with distortion of leaf tips, a condition known as tipburn, is frequently observed in strawberry. Calcium (Ca) deficiency has been considered the main cause of tipburn. The aim of the present study was to analyse the relationship between leaf mineral composition and the incidence of tipburn in three short-day strawberry (Fragaria x ananassa Duch.) cultivars ('Ventana', 'Camarosa' and 'Candonga') submitted to different concentrations of Ca. The studies were conducted in a hydroponic system in a greenhouse. Calcium was added as Ca(NO(3))(2) at 2 mM, 3 mM, 4 mM and 5 mM. A completely randomized block design (4 Ca concentrations x 3 cultivars) with three replications was used. Each replicate consisted of 12 plants grown in a polyethylene bag (100 cm x 18 cm x 3 cm) filled with coconut peat. Crown diameter and tipburn incidence were evaluated throughout the experimental period, and at the end of the experiment leaf mineral composition was assessed. In general, plants with larger crown diameters had a greater incidence of tipburn. The 'Candonga' cultivar had the smallest incidence of tipburn, while the 'Camarosa' and 'Ventana' cultivars were more susceptible. There was no correlation between level of Ca applied and incidence of tipburn. The incidence of tipburn was associated with foliar K:Ca and K:Mg ratios. Ratios above 3.40 for K:Mg and 1.77 for K:Ca represented a risk of more than 50% of tipburn incidence, when overall means for all cultivars and levels of Ca were used. (C) 2010 Elsevier B.V. All rights reserved.
- Can bicarbonate enhance the performance of carob seedlings grown in nutrient solutions with different Fe concentrations?Publication . Gama, Florinda; Correia, Pedro José; Saavedra, T.; Dandlen, Susana; de Varennes, Amarilis; Nolasco, Gustavo; Pestana, MaribelaThe aim of this work was to assess the effect of bicarbonate (Bic) ion on the nutritional status and performance of carob-tree seedlings, a species that normally grows in calcareous soil without exhibiting iron chlorosis symptoms. Seedlings were previously grown in nutrient solution with a small concentration of Fe (0.5-1 mu M) to induce a moderate chlorosis. Afterwards, two experiments were established: in experiment 1, plants were grown for 21 days in the following treatments: Fe deficiency (Fe0), 0.5 mu M Fe, 5 mu M Fe, and 5 mu M Fe plus calcium carbonate (CaCO3). After assessing these results, a second experiment was conducted for 91 days, with the following treatments: Fe0, 1 mu M Fe, 40 mu M Fe and 40 mu M Fe plus CaCO3 and sodium bicarbonate (NaHCO3). Chlorophyll of young leaves, biomass and mineral composition of leaves, stems and roots were assessed in both experiments. The ferric chelate reductase root activity (FC-R) and the genetic expression of calmodulin-regulated Ca2+-ATPase pump (ACA gene) were evaluated in experiment 2. Fe-deficient plants exhibited reduced growth and enhanced macronutrients in leaves. Root micronutrient homeostasis changed as an adaptive mechanism in carob. The addition of bicarbonate did not aggravate Fe chlorosis, as leaf chlorophyll increased significantly. Root FC-R activity and ACA gene expression was not enhanced under Fe deficiency induced by bicarbonate (Fe40 + BicNa) which suggest a positive effect of bicarbonate in the metabolism of this crop. Nevertheless, small Fe concentrations (Fe1) induced a higher ACA gene expression thus indicating some stress response signalling.
- Wild vs cultivated halophytes: Nutritional and functional differencesPublication . Castañeda-Loaiza, Viana; Oliveira, Marta; Santos, Tamara; Schüler, Lisa M.; Ribeiro Lima, Alexandre; Gama, Florinda; Salazar, Miguel; Neng, N.R.; Nogueira, J. M. F.; Varela, João; Barreira, LuísaSome halophyte plants are currently used in gourmet cuisine due to their unique organoleptic properties. Moreover, they exhibit excellent nutritional and functional properties, being rich in polyphenolics and vitamins. These compounds are associated to strong antioxidant activity and enhanced health benefits. This work compared the nutritional properties and antioxidant potential of three species (Mesembryanthemum nodiflorum, Suaeda maritima and Sarcocornia fruticosa) collected in saltmarshes from Portugal and Spain with those of cultivated plants. the latter were generally more succulent and had higher contents of minerals than plants obtained from the wild and contained less fibre. All species assayed are a good source of proteins, fibres and minerals. Additionally, they are good sources of carotenoids and vitamins A, C and B-6 and showed good antioxidant potential particularly S. maritima. Chromatographic analysis of the phenolic profile revealed that ferulic and caffeic acids as the most relevant phenolic compounds detected in the halophytes tested.
- Silencing of FRO1 gene affects iron homeostasis and nutrient balance in tomato plantsPublication . Gama, Florinda; Saavedra, Teresa; Dandlen, Susana; García‐Caparrós, Pedro; de Varennes, Amarilis; Nolasco, Gustavo; Correia, Pedro José; Pestana, MaribelaBackgroundIron chlorosis is an abiotic stress of worldwide importance affecting several agronomic crops. It is important to understand how plants maintain nutrient homeostasis under Fe deficiency and recovery. AimsWe used the virus-induced gene silencing (VIGS) method to elucidate the role of the FRO1 gene in tomato plants and identify the impact on regulation of the root ferric-chelate reductase (FCR) activity and nutritional homeostasis. MethodsTomato plantlets cv. "Cherry" were transferred into half-strength Hoagland's nutrient solution containing 0.5 & mu;M of Fe (Fe0.5). In phase I, two treatments were established: control (Fe0.5) plants and VIGS-0.5 plants corresponding to plants with the FRO1 gene silenced. In phase II, plants from Fe0.5 and VIGS-0.5 were transferred to new nutrient solution and then grown for a further 14 days under 0 and 10 & mu;M of Fe (as 0.5 & mu;M would not be enough for the larger plants during phase II). Therefore, four treatments were imposed: Fe0, Fe10, VIGS-0, and VIGS-10. ResultsVIGS-0.5 plants had significantly lower chlorophyll (Chl) and root FCR activity compared to the respective non-silenced plants and retained more Cu and Zn in the roots at the expense of stems (Cu) or young leaves (Zn). Iron concentration in roots and stems decreased in FRO1 gene-silenced plants, compared to control plants, but the allocation to different organs was similar in both treatments. ConclusionsThere was a partial recovery of leaf Chl in the VIGS-10 plants and a higher concentration of Fe in all organs. In contrast, the allocation of Cu to roots decreased in the VIGS-10 plants.
- Movimento e sinalização do ferro em plantas com estratégia IPublication . Gama, Florinda Maria Martins; Correia, Maribela Pestana; Nolasco, GustavoA deficiência de Fe provocou decréscimos no teor de clorofila total, acréscimos na atividade da QFR, alterações morfológicas a nível radicular, diminuição de absorção e translocação de Fe nos diferentes órgãos. No morangueiro o decréscimo do Fe incidiu nas raízes, na coroa e nas flores. No Poncirus o teor de Fe diminuiu nas raízes. Como alternativa à absorção de Fe ocorreu uma acumulação dos metais Zn, Mn e Cu especialmente nas raízes e folhas novas. No morangueiro os compostos orgânicos acumularam nas folhas velhas e jovens e diminuíram nas raízes. O pulso de Fe fornecido na solução nutritiva a plantas cloróticas de morangueiro levou à recuperação da deficiência em 12 dias. A partição de Fe foi direcionada para a coroa e para as flores, associado a acumulação de ácidos sucínico e cítrico ao nível radicular e permitiu maior absorção de Fe. Foram estudadas as alterações no mecanismo de resposta em plantas com o gene FRO1 silenciado. Em plantas silenciadas a deficiência de Fe levou à redução da expressão do gene, decréscimo da atividade QFR e diminuição na síntese de clorofila. Em Nicotiana o padrão de distribuição do Fe entre folhas velhas e jovens foi alterado e não foi possível recuperar as plantas silenciadas, as plantas não conseguiram retomar o metabolismo na síntese de clorofila nem ativar a enzima QFR. Foi estudado o comportamento de porta-enxertos de Poncirus com a estratégia redutora e as adaptações fisiológica ativas quando transplantadas para solo calcário. Estas plantas apresentaram desempenho semelhante em relação às plantas que cresceram numa primeira fase sem limitação de Fe indicando que os mecanismos de adaptação e o aumento nutricional induzidos pela deficiência de Fe podem ser utilizados como uma ferramenta de defesa que contribuirá para as plantas tolerarem melhor as diferentes restrições do solo em condições de campo.
- Tolerance of young (Ceratonia siliqua L.) carob rootstock to NaClPublication . Correia, P. J.; Gama, Florinda; Correia, Maribela Pestana; Martins Loução, M. A.One-year-old carob (Ceratonia siliqua L.) rootstock was grown in fertilised substrate to evaluate the effects of NaCl salinity stress. The experiment consisted of seven treatments with different concentrations of NaCl in the irrigation water: 0 (control), 15, 30, 40, 80, 120 and 240 (mmol L(-1)), equivalent to electrical conductivities of 0.0, 1.5, 2.9, 3.9, 7.5, 10.9 and 20.6 dS m(-1), respectively. Several growth parameters were measured throughout the experimental period. At the end of the experiment, pH, extractable P and K, and the electrical conductivity of the substrate were assessed in each salinity level. On the same date, the mineral composition of the leaves was compared. The carob rootstock tolerated 13.4 dS m(-1) for a period of 30 days but after 60 days the limit of tolerance was only 6.8 dS m(-1). Salt tolerance indexes were 12.8 and 4.5 for 30 and 60 days, respectively. This tolerance to salinity resulted from the ability to function with concentrations of Cl(-) and Na(+) in leaves up to 24.0 and 8.5 g kg(-1), respectively. Biomass allocation to shoots and roots was similar in all treatments, but after 40 days the number of leaves was reduced, particularly at the larger concentrations (120 and 240 mmol NaCl L(-1)). Leaves of plants irrigated with 240 mmol NaCl L(-1) became chlorotic after 30 days exposure. However, concentrations of N, P. Mg and Zn in leaves were not affected significantly (P > 0.05) by salinity. Apparently, K(+) and Ca(2+) were the key nutrients affected in the response of carob rootstocks to salinity. Plants grown with 80 and 120 mmol L(-1) of NaCl contained the greatest K. concentration. Na(+)/K(+) increased with salinity, due to an elevated Na(+) content but K(+) uptake was also enhanced, which alleviated some Na. stress. Ca(2+) concentration in leaves was not reduced under salinity. Salinization of irrigation water and subsequent impacts on agricultural soils are now common problems in the Mediterranean region. Under such conditions, carob seems to be a salt as well as a drought tolerant species. (C) 2010 Elsevier B.V. All rights reserved.
- Relationships between strawberry fruit quality attributes and crop loadPublication . Correia, P. J.; Correia, Maribela Pestana; Martinez, F.; Ribeiro, E.; Gama, Florinda; Saavedra, Teresa; Palencia, P.Crop load can influence fruit quality in several horticultural species. The aim of the present study was to determine the effect of different concentrations of calcium on crop quality traits in three short-day strawberry (Fragaria x ananassa Duch.) cultivars ('Ventana','Camarosa' and 'Candonga') and to assess the relationships between crop load and quality parameters. The studies were conducted using a hydroponic system in a greenhouse. Calcium was added as Ca(NO3)(2) at 2 mM, 3 mM, 4 mM and 5 mM. A completely randomized block design (4 Ca concentrations x 3 cultivars) with three replicates was used. Each replicate consisted of 12 plants grown in polyethylene bags (100 cm x 18 cm x 3 cm) filled with coconut peat. Titratable acidity, total soluble solids and firmness were measured throughout the experimental period. Calcium application had no effect on fruit quality attributes but the genotype effect was clear. At the end of the experiment (28th May, 2008), titratable acidity was positively related to the fresh weight of above-ground biomass and number of leaves respectively in the 'Ventana' and 'Camarosa' cultivars. Higher values of total soluble solids were found at low crop load in 'Ventana' but in 'Camarosa' this relation was not found. In 'Candonga', higher total soluble solids were linked to crop load. In 'Ventana', titratable acidity significantly decreased as crop load increased, and in 'Camarosa' high values of titratable acidity were found at different values of crop load. 'Ventana' seemed to be more sensitive to the effects of crop load patterns. Genotype was an important factor in determining fruit quality parameters. (C) 2011 Elsevier B.V. All rights reserved.
- Evaluation of Fe deficiency effects on strawberry fruit qualityPublication . Gama, Florinda; Saavedra, T.; Miguel, Maria Graça; Dandlen, S. A.The effects of Fe deficiency on the antioxidant properties of strawberry juice was carried out with a day-neutral cultivar 'Selva'. Bare root transplants (without leaves) with approximately 18 cm, were transferred to Hoagland's nutrient solution with (Fe2.5) and without Fe (Fe0), using Fe-EDDHMA as the Fe source: 0 and 2.5 5 μM Fe. Plants were grown in 20 L containers in a glasshouse for 6 weeks (from April 27 to June 5) under natural light and air temperature ≤ 25°C. Twelve transplants were used per treatment, distributed in a complete randomized design. Plants grown in absence of Fe revealed chlorotic symptoms approximately after three weeks, based on SPAD values measured in young leaves (<20). The other treatments did not show any symptoms during the experiment. Fruits were harvested from each treatment, and juice was analysed for antioxidant activity by using the free radical α-α-diphenyl-β-picrylhydrazyl capacity (DPPH•), the Trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assays. In addition, fruits were analysed for total phenols and some organic acids. The phenolic content varied between 1251 and 1514 mg gallic acid equivalents (GAE) L-1 juice, respectively, in Fe0 and Fe2.5 treatments, but with no significant differences. Despite the same total soluble solids values in both treatments, it was found that Fe depletion reduced significantly the anthocyanins and total phenols of the fruits. However, ascorbic acid increased as well as antioxidant activity expressed by both DPPH and TEAC methods.
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