RESUMO
In the present study we evaluate the effect of superparamagnetic iron oxide nanoparticles (SPIONs) carrying usnic acid (UA) as chemical cargo on the soil microbial community in a dystrophic red latosol (oxysol). Herein, 500 ppm UA or SPIONs-framework carrying UA were diluted in sterile ultrapure deionized water and applied by hand sprayer on the top of the soil. The experiment was conducted in a growth chamber at 25 °C, with a relative humidity of 80% and a 16 h/8 h light-dark cycle (600 lx light intensity) for 30 days. Sterile ultrapure deionized water was used as the negative control; uncapped and oleic acid (OA) capped SPIONs were also tested to assess their potential effects. Magnetic nanostructures were synthesized by a coprecipitation method and characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), zeta potential, hydrodynamic diameter, magnetic measurements, and release kinetics of chemical cargo. Uncapped and OA-capped SPIONs did not significantly affect soil microbial community. Our results showed an impairment in the soil microbial community exposed to free UA, leading to a general decrease in negative effects on soil-based parameters when bioactive was loaded into the nanoscale magnetic carrier. Besides, compared to control, the free UA caused a significant decrease in microbial biomass C (39%), on the activity of acid protease (59%), and acid phosphatase (23%) enzymes, respectively. Free UA also reduced eukaryotic 18S rRNA gene abundance, suggesting a major impact on fungi. Our findings indicate that SPIONs as bioherbicide nanocarriers can reduce the negative impacts on soil. Therefore, nanoenabled biocides may improve agricultural productivity, which is important for food security due to the need of increasing food production.
Assuntos
Nanopartículas de Magnetita , Nanopartículas de Magnetita/química , Solo , Nanopartículas Magnéticas de Óxido de Ferro , ÁguaRESUMO
This study analyzed the effects of UV-C radiation on the development of Rapanea ferruginea leaves. Young plants were selected at six months of age, previously identifying the leaves that had already differentiated on the 3rd, 4th, 6th 8th and 9th nodes. After the selection, the plants were divided into three groups and subjected to UV-C radiation for 30, 60 or 120 minutes. The anatomic study was made by using usual techniques of cut and coloration. The morphometric analyses were made by determining three points on the midvein of the leaf, measuring from left (L) and right (R) borders to each of those points. The symmetry deviations, maximum length and width of the limb were measured and the values were submitted to Anova and the Tukey-test (p 0.05). The responses of R. ferruginea to the UV-C were expressed by variations in the symmetry as well as morphoanatomic injuries, mainly in the palisade parenchyma and mesophyll. The differentiation of leaves did not follow a morphometric pattern, characterizing no directional asymmetry, i.e., fluctuating asymmetry. This study emphasizes the importance of multiscale observations for the determination of plant responses under stress, since several leaves showed anatomic injuries but no morphologic injuries.
Neste estudo, analisaram-se os efeitos da radiação UV-C sobre o desenvolvimento de folhas de Rapanea ferruginea. Plantas jovens foram selecionadas com seis meses de idade identificando-se as folhas já diferenciadas do 3º, 4º, 6º, 8º e 9º nó. Posteriormente, as plantas foram divididas em três grupos e submetidas à radiação UV-C por 30, 60 ou 120 min. seguidos. Para o estudo anatômico, foram utilizadas técnicas usuais de corte e coloração. As análises morfométricas foram realizadas determinando-se três pontos ao longo da nervura central da folha, medindo-se das bordas esquerda (E) e direita (D) até cada um desses pontos. Determinaram-se também os desvios de simetria, o comprimento e a largura máxima do limbo, submetendo os valores à Anova e ao teste de Tukey (p 0,05). As respostas de R. ferruginea à UV-C foram expressas por variações na simetria, bem como por injúrias morfoanatômicas, sobretudo ao parênquima paliçádico e mesofilo. A diferenciação das folhas não seguiu um padrão morfométrico, caracterizando, assim, uma assimetria não-direcional, ou seja, flutuante. Este estudo ressalta a importância de observações multiescalares para a determinação de respostas de plantas ao estresse, já que algumas folhas apresentaram danos anatômicos, porém não morfológicos.