ABSTRACT
The association between plants and arbuscular mycorrhizal fungi (AMF) can be used to bioremediate areas contaminated by metals. The objectives of this work were to evaluate the lead (Pb2+) phytoaccumulation capacity, morpho-physiology and nutrition responses of Vernonia polyanthes exposed to a solution amended with concentrations of lead nitrate and arbuscular mycorrhizal fungi. The treatments consisted of increasing doses of Pb2+ as lead nitrate [Pb(NO3)2], two strains of AMF and an absolute control without lead and AMF. Lead negatively affected some morphophysiological variables, reduced 27.3, 25.63, 30.60, and 56.60% shoot length, root collar diameter, number of leaves and leaf area, respectively, besides reducing decreasing chlorophyll a. Lead accumulated in the shoot and roots, the latter at the highest concentrations. However, the translocation factor was above 1, indicating low efficiency. The bioaccumulation factor referring to the roots were above 1. The fungi colonization rate was low, 3.31% for Gigaspora margarita and 2.33% for Acaulospora morrowiae. However, the absorption of lead increased, reflecting in lower values of chlorophyll a, dry mass of root and diameter. Results indicated that the arboreal species V. polyanthes tolerate high concentrations of lead and can accumulate significant amounts in the roots. AMF increase the accumulation of lead in the shoot and can be used in projects aimed at the phytoextraction of metals.
Subject(s)
Vernonia/cytology , Vernonia/physiology , Vernonia/chemistry , BioaccumulationABSTRACT
ABSTRACT: The lowland soils are characterized by high susceptibility to water saturation. This anaerobic condition is usually reported in paddy fields and alters the decomposition process of soil organic compounds. The aim of this study was to evaluate the soil microbial and enzymatic activity of a lowland soil at different soil moisture contents. A poorly drained Albaqualf cultivated with irrigated rice was used to evaluate microbial and enzymatic activity in treatments with different levels of soil moisture, being: i) 60% of field capacity (FC) (60%FC); ii) 100% of FC (100%FC); iii) flooded soil with a 2 cm water layer above soil surface, and iv) soil kept at 60%FC with late flood after 29 days the incubation. The greater soil microbial activity was observed in the 100%FC treatment, being 41% greater than 60%FC treatment and only 2% higher than flooded treatment. The enzymatic activity data by fluorescein diacetate (FDA) hydrolysis corroborated the higher CO2 release in treatments with higher soil moisture content. Differently from the results reported, the main methodologies to evaluate microbial activity still recommend maintenance of the soil with a moisture content close to 60% of the FC. However, in lowland soil with history of frequent paddy fields, the maintenance of moisture close to 60% of the FC can limit the microbial activity. The soil respiration technique can be used to evaluate the microbial activity in flooded soil conditions. However, further studies should be conducted to understand the effect of the cultivation history on the microbial community of these environments.
RESUMO: Os solos de várzea são caracterizados pela alta suscetibilidade à saturação por água. Esta condição anaeróbica é geralmente encontrada em solos arrozeiros e altera o processo de decomposição dos compostos orgânicos do solo. O objetivo deste estudo foi avaliar a atividade microbiana e enzimática de um solo de várzea sob diferentes teores de umidade no solo. Um Planossolo historicamente cultivado com arroz irrigado foi utilizado para avaliar a atividade microbiana e enzimática em tratamentos com diferentes níveis de umidade do solo, sendo: i) 60% de capacidade de campo (CC) (60%CC); ii) 100% da CC (100%CC); iii) solo inundado com uma camada de água de 2 cm acima da superfície do solo; e iv) solo mantido a 60%CC com inundação após 29 dias da incubação. A maior atividade microbiana do solo foi observada no tratamento 100%CC, sendo 41% maior que o tratamento 60%CC e 2% maior que tratamento inundado. Os dados da atividade enzimática pela hidrólise do diacetato de fluoresceína (FDA) corroboraram a maior liberação de CO2 nos tratamentos com maior umidade do solo. Diferentemente dos resultados encontrados, as principais metodologias para avaliação da atividade microbiana ainda recomendam manter o solo com umidade próxima a 60% da CC. No entanto, em solos de várzea com históricos de cultivos de arroz, a manutenção de umidade próxima a 60% da CC pode limitar a atividade microbiana. A técnica de respiração do solo pode ser usada para avaliar a atividade microbiana em condições de solo inundado. No entanto, mais estudos devem ser realizados para entender o efeito do histórico de cultivo na comunidade microbiana nesses ambientes.
ABSTRACT
ABSTRACT: This research aimed to evaluate the phytosociology of weeds in irrigated rice in different soil management systems and crop rotation intensity. Therefore, two field studies were carried out. Study 1 was conducted in an area that has been cultivated since 1994 with three cultivation systems: direct, pre-germinated and conventional ones. Study 2 was carried out in an experimental area in five Integrated Farming Systems, with crop rotation. Phytosociological evaluations were conducted when rice was fully blooming, in the first study, and when grain filling was ending, in the second study. Pre-germinated system of rice cultivation has predominance of aquatic weeds. Conventional system when compared with direct sowing has lower weed densities. Integrated Agricultural Production Systems with higher intensity of crop rotation have been higher infested of perennial species.
RESUMO: Este trabalho teve por objetivo avaliar a fitossociologia de plantas daninhas em arroz irrigado em diferentes sistemas de manejo do solo e intensidade de rotação de culturas. Para tanto, foram conduzidos dois estudos de campo. O primeiro estudo foi realizado em área cultivada desde 1994 com três sistemas de cultivo: plantio direto, pré-germinado e sistema convencional. O segundo estudo foi realizado em área experimental sob cinco Sistemas Integrados de Produção Agropecuária, com rotação de culturas. As avaliações fitossociológicas foram realizadas quando o arroz estava em pleno florescimento no primeiro estudo, e no final do enchimento de grãos no segundo. O sistema pré-germinado de cultivo de arroz apresenta predominância de plantas daninhas aquáticas. O sistema de cultivo convencional, quando comparado ao plantio direto, possui menores densidades de plantas daninhas. Nos Sistemas Integrados de Produção Agropecuária com maior intensidade de rotação de culturas houve maior infestação de plantas daninhas perenes.