Browsing by Author "Vieira, João"
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- Brief characterisation of Fe chlorosis in chia (Salvia hispanica L.) plants grown in nutrient solutionPublication . Vieira, João; Džidić Uzelac, Luna; Thais Fidelis Alves, Izabela; Patrício, Marco; Gama, Florinda; Saavedra, Teresa; Correia, Pedro José; Pestana, MaribelaChia (Salvia hispanica L.) plant is a well-known plant due to the nutraceutical value of its seeds. The aim of this preliminary study was to assess the response of Chia plants to Fe deficiency. Chia plants were grown for 12 days in Hoagland's nutrient solutions without Fe (Fe0) and with Fe (Fe10-10 mu M Fe). Biomass parameters and root ferric chelate-reductase activity (FC-R; EC 1.16.1.17) were determined at the end of the experiment. Chlorophyll estimations (expressed as SPAD readings) decreased progressively, showing the typical symptoms of iron chlorosis. In addition, iron-deficient chia plants exhibit smaller biomass (number of leaves, root, and shoot growth reduction) compared to control plants. These plants also showed morphological changes in roots. Furthermore, root FC-R activity was significantly lower in Fe0 plants.
- Enhancing growth, nutrient uptake and flowering of Tagetes patula plants through the application of suspensions of Chlorella vulgarisPublication . Vieira, João; Saque, Moisés; Viana, Catarina; Rodrigues, Maria Helena; Guerreiro David Coelho, Luísa Isabel; Gama, Florinda; Varela, João; Pereira, Hugo; Reis, Mário; Pestana, Maribela; Correia, Pedro JoséTagetes patula L. is a prominent plant that is frequently used for its ornamental value. Marigolds are sources of various compounds of great interest to agricultural, pharmaceutical, and nutritional industries. Microalgae can be applied as a biostimulant as they have multifunctional properties in agriculture, namely facilitating nutrient uptake, improving crop performance and physiological status, and thus increasing tolerance to abiotic stress. This study evaluated the efect of applying Chlorella vulgaris as a plant biostimulant on the growth and fowering of T. patula plants. Microalgae suspensions were applied to the substrate at concentrations of 0.5, 2.0 and 5.0 g dry weight (DW) L−1. A set of plants without the application of microalgae was used as control. The use of microalgae had a positive impact on plant growth. Specifcally, C. vulgaris application resulted in greater height, while the highest concentration (5.0 g DW L−1) resulted in higher fresh weight. Microalgae application signifcantly promoted the earlier fowering of marigolds. The macronutrient and micronutrient values were statistically similar between the control plants and those treated with microalgae. When considering only the treated plants, there was a signifcant correlation between the concentration of C. vulgaris and the concentrations of N, P, Mn and Cu in the shoots of T. patula plants. Plants receiving higher concentrations of C. vulgaris exhibited higher levels of these nutrients. These results highlight the potential use of Chlorella vulgaris as an efective biostimulant for enhancing the growth, fowering, and nutrient uptake of T. patula, ofering valuable applications for improving ornamental plant production and, ultimately, agricultural sustainability.
- Mixed analytical and numerical modelling of an oceanic peninsulaPublication . Nunes, Luís; Dill, Amélia Maria Mello de Carvalho; Ribeiro, Luís; Vieira, JoãoAnalytical and numerical models were applied to an oceanic peninsula to estimate the volume of freshwater available, and the amount of water that could be pumped without depleting the resource. The analytical models were used at regional scale, whereas the numerical models were applied in a small domain to obtain the hydrogeologic parameters of the aquifer. The results showed that even small pumping rates of 10% of the annual net recharge would have important impacts in the thickness of the water lens, which can be even higher during dry years, when the annual recharge may be half of the multiple-year long-term average value.
- Screening of sustainable groundwater sources for integration into a regional drought-prone water supply systemPublication . Stigter, T. Y.; Monteiro, José Paulo; Nunes, L.; Vieira, João; Cunha, Maria da Conceição; Ribeiro, Luís; Nascimento, João; Lucas, HelenaThis paper reports on the qualitative and quantitative screening of groundwater sources for integration into the public water supply system of the Algarve, Portugal. The results are employed in a decision support system currently under development for an integrated water resources management scheme in the region. Such a scheme is crucial for several reasons, including the extreme seasonal and annual variations in rainfall, the effect of climate change on more frequent and long-lasting droughts, the continuously increasing water demand and the high risk of a single-source water supply policy. The latter was revealed during the severe drought of 2004 and 2005, when surface reservoirs were depleted and the regional water demand could not be met, despite the drilling of emergency wells. For screening and selection, quantitative criteria are based on aquifer properties and well yields, whereas qualitative criteria are defined by water quality indices. These reflect the well’s degree of violation of drinking water standards for different sets of variables, including toxicity parameters, nitrate and chloride, iron and manganese and microbiological parameters. Results indicate the current availability of at least 1100 l s−1 of high quality groundwater (55% of the regional demand), requiring only disinfection (900 l s−1) or basic treatment, prior to human consumption. These groundwater withdrawals are sustainable when compared to mean annual recharge, considering that at least 40% is preserved for ecological demands. A more accurate and comprehensive analysis of sustainability is performed with the help of steady-state and transient groundwater flow simulations, which account for aquifer geometry, boundary conditions, recharge and discharge rates, pumping activity and season. (tibor.stigter@ist.utl.pt) ality. They permit an advanced analysis of present and future scenarios and show that increasing water demands and decreasing rainfall will make the water supply system extremely vulnerable, with a high risk of groundwater salinization and ecosystem degradation.
- The water crisis in southern Portugal: how did we get there and how should we solve itPublication . Nunes, Luís; Monteiro, José Paulo; Cunha, Maria da Conceição; Vieira, João; Lucas, Helena; Ribeiro, LuísUntil very recently, public water supply in the Algarve region was almost entirely supported by groundwater wells. However, in the last years of the XX Century, the Portuguese central administration defined a scheme for the public water supply sector entirely based in surface water from large dams, in order to guarantee the public water supply. The efforts to abandon groundwater as a source for public supply started in 1998, after a large investment in new infrastructures and rehabilitation of other ones. However, the practical implementation of this water supply scheme showed that an integrated resource management is needed in order to implement a more economical and reliable solution. The present paper describes the historical background and the evolution of water use in the last decades until the present time in the Algarve, and a proposal for restructuring the management of the water supplies based in the development of a decision support system in the scope of an integrated water resources management.