Browsing by Author "Saavedra, Teresa"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- A caracterização e correção da deficiência de ferro em plantas de morangueiro: novas abordagensPublication . Pestana, Maribela; Gama, Florinda; Saavedra, Teresa; Pinto, João Castro; Abadia, Anunciación; Varennes, A.; Correia, Pedro JoséIron (Fe) is abundant in soils and although it is required in small amounts by plants the incidence of iron chlorosis (Fe deficiency) is very common in a number of crops and requires massive soil application of Fe-chelates to correct it. In this work, we present the most important results obtained in several experiments conducted with strawberry to study the physiological and biochemical response mechanisms to Fe deficiency, and the assessment of novel alternatives to control this nutritional disorder. In all experiments, conducted in hydroponic systems, symptoms were induced by withdrawing Fe from the solution and the results were compared to a control treatment grown with Fe. The degree of chlorosis and symptoms recovery was estimated using SPAD values. The activity of iron chelate reductase, the enzyme responsible for Fe reduction in roots, was determined in root apices by colorimetric quantification of the BPDS complex. The Fe concentration in leaves and roots was quantified by atomic absorption spectrophotometry after treatments at 450 ºC and acid digestion of the ashes obtained. Strawberry plants that grew always without Fe, presented Fe chlorosis and morphological external root modifications associated with increases of the activity of the Fe-reductase enzyme. The recovery of chlorotic plants was achieved by application of Fe sulphate either to leaves or to the nutrient solution. In plants recovered by using Fe in the solution, the enzyme maintained a large activity, suggesting a strategy to increase plant Fe pools. As an alternative to synthetic Fe chelates, we also tested a foliar application of a plant extract obtained from fresh grass clippings (national patent PT/103584-2009 of UALG, and international patent PCT/PT2007/000041-2008, UALG and ADPFertilizantes), which was effective in chlorosis recovery after three applications. The results are discussed in order to highlight the practical implications of these responses under a perspective of optimization of crop Fe fertilization
- Development and recovery of iron deficiency by iron resupply to roots or leaves of strawberry plantsPublication . Pestana, Maribela; Correia, Pedro José; Saavedra, Teresa; Gama, Florinda; Abadia, Anunciación; Varennes, A.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.
- Fe deficiency induction in Poncirus trifoliata rootstock growing in nutrient solution changes its performance after transplant to soilPublication . Gama, Florinda; Saavedra, Teresa; Díaz, Isabel; Campillo, Maria del Carmen; Varennes, Amarilis de; Duarte, Amílcar; Pestana, Maribela; Correia, José PedrotThe absence of iron (Fe) in the nutrient solution induces several physiological and morphological adapta-tions in the roots of Poncirus trifoliata, a citrus rootstock, thereby modifying its overall nutritional status.Whether these changes are advantageous when plants are transplanted to calcareous soils needs to beassessed. To achieve this objective a two-phase experiment was established, first in nutrient solution(phase I) then in pots containing different soils (phase II). In phase I, P. trifoliata L. Raf. plants were grownin Hoagland’s solution with 120 M of Fe (Fe120 treatment) or without (Fe0 treatment). At the end ofphase I (87 days), Fe-chlorotic plants had less chlorophyll in apical younger leaves, root tips were swollenand their FC-R activity was enhanced, typical responses to Fe-stress. Chlorotic plants had less Fe com-pared to control plants, but accumulated more Cu and Zn. In contrast the root to shoot ratio (dry weight)and the amounts of macronutrients were not affected by Fe chlorosis. In phase II, plants of both treat-ments were transplanted to pots containing a calcareous (C) or a non-calcareous (nC) soil resulting in fourtreatments: Fe0nC, Fe120nC, Fe0C and Fe120C. From the end of phase I until the end of the experiment(353 days), the calcareous soil negatively affected the overall nutritional balance in both Fe0 and Fe120treatments. Apparently, the ability to change metal homeostasis in particular Cu, as a Fe-stress responsewas maintained in plants grown in non-calcareous soil. Moreover, the previous induction of physiologi-cal and morphological adaptations to Fe depletion alleviated the iron chlorosis symptoms caused by soilcarbonates. These results may point to the utilization of internal stress signalling as a tool to cope withdifferent soil conditions
- The memory of iron stress in strawberry plantsPublication . Gama, Florinda; Saavedra, Teresa; Silva, José Paulo da; Miguel, Maria Graça; Varennes, Amarilis; Correia, Pedro José; Pestana, MaribelaTo 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 mM 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 mM 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.