Effects of plant density and the number of emitters on plant growth and nitrate concentration in spinach cultivated in substrate

The effects of plant density and the number of emitters per Styrofoam box on plant growth and nitrate (NO3-) concentration were evaluated in spinach (Spinacia oleracea L. cv. Tapir). Spinach seedlings were transplanted at 45 days after emergence into Styrofoam boxes filled with the substrate and were grown during winter in an unheated greenhouse with no supplemental lighting. The experiment was carried out with four treatments, including two plant densities (160 and 280 plants/m2) and two number of emitters per Styrofoam box (4 and 8 emitters). Each planting box was irrigated daily and fertigated with a complete nutrient solution. Shoot dry weight was not affected by plant density. However, yield increased with plant density and emitter number. Leaf-blade NO3- concentration was not affected by the interaction between plant density and number of emitters, but petioles NO3- concentration was greater in treatment with 160 plants/m2 and 8 emitters. Although leaf-blade NO3- concentration was not affected by plant density, it decreased with the number of emitters. On the other hand, petiole NO3- concentration was not affected by plant density or number of emitters. Leaf-blade NO3- concentration ranged from 3.2 to 4.1 mg/g fresh weight, occurring the highest value in the treatment with 280 plants/m2 and 4 emitters. Petiole NO3- concentration ranged from 3.5 to 5.3 mg/g fresh weight, values that were higher than allowed by EU regulation.

Effects of substrate type on plant growth and nitrogen and nitrate concentration in spinach

Abstract The effects of three commercial substrates (a mixture of forest residues, composted grape husks, and white peat, black peat and coir) on plant growth and nitrogen (N) and nitrate (NO3) concentration and content were evaluated in spinach (Spinacia oleracea L. cv. Tapir). Spinach seedlings were transplanted at 45 days after emergence into Styrofoam boxes filled with the substrates and were grown during winter and early spring in an unheated greenhouse with no supplemental lighting. Each planting box was irrigated daily by drip and fertilized with a complete nutrient solution. The NO3 content of the drainage water was lower in coir than in the other substrates. However, shoot NO3 concentration was not affected by substrate type, while yield and total shoot N and NO3 content were greater when plants were grown in peat than in the mixed substrate or the coir. Leaf chlorophyll meter readings provided a good indication of the amount of N in the plants and increased linearly with total shoot N. Keywords Spinacia oleracea; chlorophyll meter; coir; peat; soilless culture systems

Effects of substrate type on plant growth and nitrogen and nitrate concentration in spinach.

The effects of three commercial substrates (a mixture of forest residues, composted grape husks, and white peat, black peat and coir) on plant growth and nitrogen (N) and nitrate (NO3) concentration and content were evaluated in spinach (Spinacia oleracea L. cv. Tapir). Spinach seedlings were transplanted at 45 days after emergence into Styrofoam boxes filled with the substrates and were grown during winter and early spring in an unheated greenhouse with no supplemental lighting. Each planting box was irrigated daily by drip and fertilized with a complete nutrient solution. The NO3 content of the drainage water was lower in coir than in the other substrates. However, shoot NO3 concentration was not affected by substrate type, while yield and total shoot N and NO3 content were greater when plants were grown in peat than in the mixed substrate or the coir. Leaf chlorophyll meter readings provided a good indication of the amount of N in the plants and increased linearly with total shoot N.

Effects of nitrogen level on purslane antioxidant activity.

The high antioxidant activity of purslane, Portulaca oleracea L., gives it a high nutritional and functional value. The commercial production of purslane has increased in Portugal, making it necessary to know the effects of inputs, mainly nitrogen, on the antioxidant activity. The main goal of this study was to evaluate the influence of nitrogen application on purslane antioxidant activity. The experiment was carried out with for treatments: 30, 60 and 90 kg/ha of nitrogen. Plants of golden-leaf purslane were grown in Styrofoam-boxes filled with substrate and fertigated two times per week, over four weeks with ammonium nitrate solution (16.9% NO3-N and 16.7 NH4+-N). The increase in the nitrogen level decreased the water-soluble proteins content. However the ascorbate, phenols content as well as antioxidant activity measured by FRAP method was not affected by nitrogen level. Plants shoot antioxidant activity, measured by DPPH method decreased significantly in the treatment with 90 kg N/ha (26.20 g/g gallic acid). On the other hand, plant shoot antioxidant activity mediated by peroxidases was higher in treatment 30 kg N/ha (0.459 µmol min-1/mg prot.). Application of 60 kg N/ha allowed a vigorous plant growth without disturb its antioxidants and conservation properties.

Fitoextracção de cádmio de solos contaminados, com plantas seleccionadas

A remediação de locais contaminados com metais pesados usando plantas hiperacumuladoras aparenta ser uma alternativa bastante viável. Neste trabalho comparou-se a acumulação e tolerância ao cádmio (Cd), ambas baseadas nas respostas ao stress oxidativo em três espécies de plantas diferentes: Brassica juncea (L.) Czem., Nicotiana tabacum L. e Solanum nigrum L., descritas na literatura como plantas bastante tolerantes ou até com características híper acumuladoras. As plantas cresceram num solo contaminado com diferentes concentrações de Cd (O- 35 mg kg-1) durante um período de 90 dias. O factor de translocação (FT), utilizado para medir a translocação efectiva do Cd da raiz para a parte aérea, variou consideravelmente entre as espécies desenvolvidas. A N. tabacum foi a planta que apresentou os maiores valores de FT. Neste trabalho foi a única planta que preencheu todas as condições para ser considerada hiperacumuladora para todos os níveis de contaminação do solo. Por outro lado, a S. nigrum apresentou os maiores valores de concentração de Cd nos tecidos, com um FT > 1, na presença de 5 mg Cd kg·1 de solo. Apesar da B. juncea ter apresentado um resultado de FT inferior às restantes, foi a única planta com valores crescentes de FT com o aumento da contaminação de Cd. O stress oxidativo nas plantas desenvolvidas foi avaliado pela peroxidação lipídica e pelas actividades da catalase (CAT), ascorbato peroxidase (APX), guaiacol peroxidase (GPX) e superóxido dismutase (SOO), quer na raiz quer na parte aérea. Foi observado um aumento significativo (versus controlo) na peroxidação lipídica e actividade enzimática da CATe APX na parte aérea da B. juncea, N. tabacum e S. nigrum para os níveis de contaminação mais elevados, 15 e/ou 35 mg Cd kg-1 A B. juncea apresentou maior sensibilidade na resposta da GPX, para todas as concentrações de Cd no solo. A peroxidação lipídica e a actividade da CAT foram superiores na parte aérea em relação à raiz para todas as plantas em todas as contaminações de Cd presentes no solo. A actividade da SOO não apresentou respostas consistentes para nenhuma das plantas. ABSTRACT: Remediation of sites contaminated with heavy metals using hyper accumulators seems a promising alternative to engineering approaches. ln this work, we compared cadmium (Cd) accumulation and tolerance (based on responses to oxidative stress) in three different species, Brassica juncea (L) Czem., Nicotiana tabacum L. and Solanum nigrum L., described in the literature as very tolerant or even as hyper accumulators. The plants were grown in soil spiked with different Cd concentrations (O- 35 mg kg- 1) over a period of 90 days. The translocation factor (TF), used to measure the effectiveness of translocating Cd from roots to shoots, depended greatly on the species. N. tabacum was the plant which exhibited the highest TF values. lt was the only plant under study that fulfilled the conditions of a hyper accumulator for all levels of soil contamination. On the other hand, S. nigrum presented the highest Cd concentration in plant tissues, with TF > 1 in the presence of 5 mg Cd kg-1 of soil. Although B. juncea had presented the lowest TF and Cd concentrations, it was the only plant with TF values increasing with the level of cadmium. Oxidative stress in plants was evaluated by lipid peroxidation and activities of catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and superoxide dismutase (SOO), both in roots and shoots. A significant enhancement (versus control) on lipid peroxidation and enzymatic activity of CAT and APX in shoots of B. juncea, N. tabacum and S. nigrum was observed for the highest levels of Cd in soil, 15 and/or 35 mg Cd kg-1. B. juncea presented the most sensitive response of GPX, for all levels of Cd in soil. Lipid peroxidation and CAT activity were greater in shoots than in roots for all plants and soil Cd concentrations. SOO activity did not present consistent trends for any plant.

Estratégias de fitorremediação de duas minas abandonadas - Tinoca e Mostardeira

O presente trabalho teve como objectivo a implementação de estratégias de remediação de duas minas abandonadas na região do Alto Alentejo, a mina da Tinoca e a mina da Mostardeira. Neste trabalho foram realizados ensaios de fitoremediação com as espécies Brassica juncea (L.) Czern, Solanum nigrum L., Piptatherum miliaceum (L.)Coss. e Spergularia purpurea (Persoon)G. Don fil. As misturas utilizadas como suporte para desenvolvimento das plantas resultaram da mistura (1:1) de resíduos de escombreira e solo. Estas misturas foram realizadas para as duas minas independentemente. A estas misturas foram adicionados correctivos minerais e um correctivo orgânico. Dos estudos realizados observou-se que medidas de atenuação/diluição não se mostraram suficientemente eficazes para permitir uma estabilização da zona superficial em causa, pelas espécies de plantas estudadas. Por outro lado, a adição de um correctivo orgânico, juntamente com a subida do pH do solo, conduziu a um melhoramento das características físicas e químicas das misturas originais facilitando a sua revegetação. ABSTRACT: This study was designed to implement remediation strategies in two abandoned mines in the region of Alto Alentejo, the Tinoca mine and Mostradeira mine. Phytoremediation tests were carried out with the species Brassica juncea (L.) Czern, Solanum nigrum L., Piptatherum miliaceum (L.) Coss. and Spergularia purpurea (Persoon) G. Don fil. The mixtures used to support plant growth resulted from the admixture (1:1) of waste tailings and soil and were performed independently for the two mines. Soil mineral correctives and organic fertilizers were added to these mixtures. The study showed that mitigation/dilution measures were not sufficiently effective to allow the stabilization of the area with the plant species studied. However, the addition of an organic corrective, along with the rise of soil pH, led to an improvement in the physical and chemical properties of the original amendment soil mixtures, hence facilitating its phytorestoration.