Although silicon (Si) is not an essential element, it presents a close relationship with the alleviation of heavy‐metal toxicity to plants. This work was carried out to evaluate the effects of Si application to soil on the amelioration of metal stress to maize grown on a contaminated soil amended with Si (0, 50, 100, 150, and 200 mg kg–1) as calcium silicate (CaSiO3). Additionally, the cadmium (Cd) and zinc (Zn) bioavailability as well as their distribution into soil fractions was also studied. The results showed that adding Si to a Cd‐ and Zn‐contaminated soil effectively diminished the metal stress and resulted in biomass increase in comparison to metal‐contaminated soil not treated with Si. This relied on Cd and Zn immobilization in soil rather than on the increase of soil pH driven by calcium silicate application. Silicon altered the Cd and Zn distribution in soil fractions, decreasing the most bioavailable pools and increasing the allocation of metals into more stable fractions such as organic matter and crystalline iron oxides.
Arsenic is a metalloid highly toxic to plants and animals, causing reduced plant growth and various health problems for humans and animals. Silicon, however, has excelled in alleviating stress caused by toxic elements in plants. The aim of this study was to investigate the effects of Si in alleviating As stress in maize plants grown in a nutrient solution and evaluate the potential of the spectral emission parameters and the red fluorescence (Fr) and far-red fluorescence (FFr) ratio obtained in analysis of chlorophyll fluorescence in determination of this interaction. An experiment was carried out in a nutrient solution containing a toxic rate of As (68 μmol L -1 ) and six increasing rates of Si (0, 0.25, 0.5, 1.0, 1.5, and 2.0 mmol L -1 ). Dry matter production and concentrations of As, Si, and photosynthetic pigments were then evaluated. Chlorophyll fluorescence was also measured throughout plant growth. Si has positive effects in alleviating As stress in maize plants, evidenced by the increase in photosynthetic pigments. Silicon application resulted in higher As levels in plant tissue; therefore, using Si for soil phytoremediation may be a promising choice. Chlorophyll fluorescence analysis proved to be a sensitive tool, and it can be successfully used in the study of the ameliorating effects of Si in plant protection, with the Fr/FFr ratio as the variable recommended for identification of temporal changes in plants.
A Sub-Bacia Hidrográfica do Rio Piauitinga é uma área que vem sofrendo diversas transformações ambientais ao longo do tempo em consequência de constantes desmatamentos. O presente trabalho foi realizado com a finalidade de conhecer a composição florística arbóreo-arbustiva, a estrutura fitossociológica e identificar usos e ocupação dos solos das áreas de nascentes do Alto Rio Piauitinga, situadas no município de Lagarto-SE. As análises foram realizadas em um raio de 50m no entorno das nascentes, por meio de censo populacional, contabilizando todos os indivíduos arbustivo-arbóreos vivos com diâmetro à altura do peito (DAP a 1,30m do solo) ≥ 5,0 cm. Registrou-se 1.470 indivíduos, distribuídos em 75 espécies, 57 gêneros e 32 famílias botânicas. Os índices de diversidade (H’) e equabilidade (J’), encontrados foram respectivamente, 3,04 nats.ind-1 e 0,71. A similaridade florística (SJ) variou de 0,08% a 56,2%. A densidade total foi de 104,034 ind.ha-1 e a área basal de 32,21 m².ha-1. Verificou-se apenas uma nascente em estado de preservada, seis perturbadas e 19 degradadas; 22 são pontuais e quatro difusas. E que estão ocupadas principalmente por áreas agrícolas e de pastagens. É possível inferir que as nascentes se encontram em processo de perca de qualidade e produção de suas águas.
The salinization process in irrigated areas in the semi-arid region of Brazil, constantly cause economic, social, and environmental problems. Therefore, the present research aimed at assessing the effect of different amounts of agricultural gypsum and cow manure associated with an artificial drainage system and salt leaching due to the application of amount of water in a saline-sodic soil under field condition. The experiment was carried out at the irrigated perimeter of Jacaré-Curituba, Poço Redondo, with an experimental design split into plots made of doses of gypsum corresponding to 0,0; 4,300.00 and 8,600.00 kg.ha-1 combined with and without organic matter, cow manure with 25,000.00 kg.ha-1 and 0.00 kg.ha-1. Each treatment (six in total) was repeated four times. Thus, 24 plots of 50 m2 were monitored (split plot) with an area of 1.200 m2. All treatments had an artificial drainage system in the center of the plot and the same amount of leach water was then added. The outcomes allowed us to understand that all treatments had the salinity and sodicity soil values reduced at the studied site. Moreover, the treatments with cow manure (source of organic matter) presented the best results, because soil electrical conductivity values (< 4 dS m-1) reached the normal level to agricultural yield.
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