Francisco de Assis de Oliveira

On the thermal limits for the use of stingless bees as pollinators in commercial greenhouses

Stingless bees (Apidae, Meliponini) are frequently used as crop pollinators in tropical countries. The present study calls attention to the thermal limit for the use of these bees as pollinators in commercial greenhouses, in which the temperature frequently exceeds that of the outside environment. We assessed the thermal biology of Melipona subnitida, a stingless bee species that naturally occurs in north-eastern Brazil, a region characterized by elevated ambient temperatures all year round. The critical (CTN) and lethal limits (LTN) for worker bees under long-term temperature exposure (24 h) were 40 and 44 °C respectively when individuals had access to water, or 39 and 42 °C respectively without water. Due to limited active colony thermoregulation of this species, the temperatures inside the nests were similar to the ambient temperature. In their natural environment, nest temperatures never exceeded CTN. In strong contrast, inside a greenhouse, the nest temperatures exceeded the critical value nearly every day due to the high ambient temperatures in this closed environment. As a result, the colonies weakened critically and had to be removed from the greenhouse after 14 days. Our study emphasizes the need for both thermo-physiological investigations and management strategies when planning the use of bees as pollinators for greenhouse crops, particularly so in tropical regions, where temperatures in these enclosed environments may easily exceed the thermal limits of a species.

Uso de bioestimulante como agente amenizador do estresse salino na cultura do milho pipoca

O uso de bioestimulantes tem se difundido na agricultura brasileira, promovendo o crescimento e aumento na produtividade das culturas, mas ainda sao incipientes estudos sobre o uso destas substâncias em plantas sob estresse, principalmente sobre estresse salino. Objetivou-se avaliar o uso de bioestimulante como agente amenizador do estresse salino na cultura do milho pipoca. O experimento foi conduzido em ambiente protegido no Campus da Universidade Federal Rural do Semi-Arido, em Mossoro-RN. Utilizou-se o delineamento experimental inteiramente casualizado, com os tratamentos distribuidos em esquema fatorial 2 x 4, referentes a dois niveis de salinidade da agua de irrigacao (0,5 e 4,5 dS m-1) e quatro doses de bioestimulante aplicado via tratamento de sementes (0; 5; 10 e 20 mL kg-1 de sementes), com cinco repeticoes. Utilizou-se o bioestimulante comercial Stimulate® (0,009% citocinina, 0,005% giberelina e 0,005% de auxina) e as plantas foram coletadas aos 50 dias apos a semeadura. Foram avaliadas as seguintes variaveis: altura de plantas, diâmetro do colmo, numero de folhas, area foliar, massa seca de colmo, massa seca de folhas, massa seca de raiz, massa seca de pendao, massa seca total e area foliar especifica. O uso de agua salina na irrigacao provocou reducao na maioria das variaveis de crescimento do milho doce, independentemente do tratamento de sementes com bioestimulante. O tratamento de sementes com Stimulate® promove o desenvolvimento de plantas de milho pipoca, mais nao inibiu nem amenizou o efeito da salinidade sobre as plantas.

Tolerância do maxixeiro, cultivado em vasos, à salinidade da água de irrigação

Gherkin (Cucumis anguria) is an important crop in the North and Northeast regions of Brazil, and its production is predominantly from spontaneously growing plants. For this reason, little research is done on the crop, especially regarding the effect of salinity. This study was conducted at the Federal Rural University of the Semiarid (UFERSA) in Mossoro, RN, to evaluate the effect of different salinity levels of irrigation water on the development and yield of gherkin. The experiment was arranged in a completely randomized design, with four treatments (salinity levels of irrigation water: S1-0.5, S2-2.0, S3-3.5 and S4-5.0 dS m-1). There were five harvests of fruits and at the end of the experiment the plants were collected and analyzed for major development parameters and yield. We evaluated the following variables: length of the main branch, stem diameter, number of leaves, leaf area, dry mass of leaves, stems, fruits and total fruit number, average fruit weight and yield. The results showed that gherkin is sensitive to salinity. Significant responses were found for all variables that reduced with increasing salinity.

AVALIAÇÃO QUALITATIVA DE IMPACTOS AMBIENTAIS CONSIDERANDO AS ETAPAS DE LIMPEZA E PREPARO DO TERRENO EM PLANTIOS FLORESTAIS NO NORDESTE PARAENSE

RESUMO – Este trabalho apresenta os resultados da avaliacao qualitativa de impactos ambientais na etapa de implantacao florestal, considerando-se as atividades de limpeza e preparo do terreno, por meio da aplicacao dos metodos de matriz de identificacao e interacao de impactos, da lista descritiva (checklist) e da combinacao/ ponderacao de atributos. Tal avaliacao foi feita com base na identificacao e caracterizacao qualitativa dos impactos ambientais, cujas metodologias possibilitaram a visualizacao rapida e hierarquizada dos impactos. Atraves dessa matriz, evidenciaram-se 348 possiveis relacoes de impactos (capacidade total da matriz), das quais 304 (87,6%) foram identificadas, em que 209 impactos (60,05%) recairam sobre o meio biofisico e 95 (27,31%) sobre o meio socioeconomico. Dos 209 impactos no meio biofisico, todos apresentaram valor negativo, evidenciando-se ser esse o compartimento ambiental mais impactado negativamente quando da realizacao das atividades de limpeza e preparo do terreno. Ja, dos 95 impactos no meio socioeconomico, 72 (75,78%) foram de valor positivo e 23 (24,21%) de valor negativo, demonstrando que o meio socioeconomico e o compartimento ambiental mais afetado positivamente por ocasiao da realizacao das atividades. Foram identificados os impactos ambientais positivos e negativos mais significantes que, com a combinacao/ponderacao de atributos, mostraram ser, em sua maioria, de significância media local e regional. Todos os impactos evidenciados apresentaram temporalidade no curto prazo, evidenciando estarem sobre o alcance quanto ao diagnostico e gestao ambiental adequados. Os resultados contribuem e reafirmam a necessidade de se instituir o processo de avaliacao de impactos ambientais na rotina tecnico-administrativa da empresa como instrumento de gestao ambiental.

Crescimento de mudas de moringa em função da salinidade da água e da posição das sementes nos frutos

Choosing seeds is crucial for obtaining good quality seedlings, especially when the seedlings are grown under adverse environmental conditions. This work was carried out to evaluate the influence of salinity on the development of moringa seedlings from seeds located at different positions in the pod. The design used in this study was a completely randomized design with treatments arranged in 3 x 4 factorial scheme, with four replications. The treatments resulted from a combination of three positions in the seed fruit (basal, median and apical) with four salinity levels of irrigation water (0.5, 2.0, 3.5 and 5.0 dS m-1). The growth characteristics evaluated were the following: height (ALT), stem diameter (AD), diameter of the root principal (DRP), number of leaves (NL), leaf area (LA), shoot dry mass (SDM), root dry mass (RDM) and total dry mass (MST). The data were submitted to analysis of variance by F test and means were compared by the Tukey test at 5% of probability for the effect of seed position in the fruits, and to regression analysis for data from the salinity. Interaction was significant for most traits. The salinity of irrigation water caused a reduction in all variables. Seedlings from seeds located in the basal portion of the fruits are more affected by salinity of irrigation water.

The partial root-zone saline irrigation system and antioxidant responses in tomato plants

Salinity is a limiting factor that can affect plant growth and cause significant losses in agricultural productivity. This study provides an insight about the viability of partial root-zone irrigation (PRI) system with saline water supported by a biochemical approach involving antioxidant responses. Six different irrigation methods using low and high salt concentrations (S1-0.5 and S2-5.0 dS m-1) were applied, with or without PRSI, so that one side of the root-zone was submitted to saline water while the other side was low salinity water irrigated. The results revealed different responses according to the treatments and the PRSI system applied. For the treatments T1, T2 and T3, the PRSI was not applied, while T4, T5 and T6 treatments were applied with PRSI system. Lipid peroxidation, proline content, and activities of SOD, CAT, APX, GR and GSH in tomato plants subjected to PRSI system were analyzed. Plant growth was not affected by the salt concentrations; however, plants submitted to high salt concentrations showed high MDA content and Na+ accumulation when compared to the control plants. Plants submitted to treatments T4, T5 and T6 with PRSI system exhibited lower MDA compared to the control plants (T1). Proline content and activities of SOD, CAT, APX, GR and GSH content were maintained in all treatments and tissues analyzed, with only exception for APX in fruits and GSH content, in roots. The overall results showed that PRSI system could be an applicable technique for saline water supply on irrigation since plants did not show to be vulnerable to salt stress, supported by a biochemical approach involving antioxidant responses.

Diversidade de artrópodes da fauna edáfica em agroecossistemas de estabelecimento agrícola familiar na Amazônia Oriental

Os agroecossistemas, suas composicoes vegetais e diferentes formas de manejo apresentam nos artropodes da fauna edafica os elementos fundamentais para seu funcionamento, de forma que o conhecimento destas comunidades e subsidio importante para perspectivas de manejo sustentavel dos agroecossistemas amazonicos. Neste contexto, o objetivo e avaliar a diversidade de artropodes da fauna edafica em agroecossistemas com diferentes usos do solo em estabelecimento agricola familiar na Amazonia Oriental. As avaliacoes foram realizadas no municipio de Maraba-PA. Em quatro agroecossistemas (area de policultivo, floresta, mandiocal e pastagem) os artropodes da fauna edafica foram coletados com armadilhas de solo. Foram realizadas seis amostragens em funcao da sazonalidade climatica regional. Foram calculados para os diferentes agroecossistemas a abundância e a riqueza de morfoespecies, alem de indices de diversidade, dominância, equitabilidade e similaridade. Foram capturados 24.564 individuos nas seis amostragens nos quatro agroecossistemas abrangendo 266 morfoespecies. O mandiocal destacou-se em abundância de individuos (13.041) e a pastagem apresentou os menores valores para abundância total (3.895). Os grupos taxonomicos Hymenoptera, Coleoptera e Acari foram responsaveis por 94,52% da abundância total de individuos e a area de policultivo apresentou a maior diversidade de artropodes da fauna edafica, com o indice de diversidade de Shannon igual a 2,93. A diversidade da fauna edafica foi influenciada pelas coberturas vegetais nos diferentes agroecossistemas. O manejo sem uso do fogo na area de policultivo proporcionou maior diversidade de artropodes da fauna edafica, enquanto que a pastagem apresentou caracteristicas de degradacao com a menor diversidade observada.

Quality in the pepper under different fertigation managements and levels of nitrogen and potassium

The rational use of nutrients is of fundamental importance for obtaining high productivity of high nutritional quality. This work was developed with the aim of evaluating the quality of pepper fruit grown under different fertigation managements and different levels of nitrogen and potassium. The experimental design was of randomised blocks in a 3 x 6 factorial scheme with four replications. The treatments resulted from the combination of three fertigation managements (M 1 -based on the rate of absorption; M 2 -monitoring the conductivity of the soil solution; M 3 -monitoring concentrations of N and K ions in the soil solution) with six levels of N and K (N 0 K 0 , N 50 K 50 , N 100 K 100 , N 150 K 150 , N 200 K 200 and N 300 K 300 ) as a percentage of the recommended dosage for the crop under conventional fertigation (M 1 ) or hydroponics (M 2 and M 3 ). Fruit quality was evaluated for the following characteristics: pH, soluble solids, titratable acidity, vitamin C content and the ratio of soluble solids to titratable acidity. The different fertigation managements only affected the levels of soluble solids (SS) and titratable acidity (TA), reducing the SS and TA. The variables under study were adjusted for the levels of N and K using quadratic models.