Bark is a structure involved in multiple physiological functions, but which has been traditionally associated with protection against fire. Thus, little is known about how the morpho-anatomical variations of this structure are related to different ecological pressures, especially in tropical savanna species, which are commonly subjected to frequent fire and drought events. Here we evaluated how the structural and functional variations of bark are related to the processes of resilience and resistance to fire, as well as transport and storage of water in 31 native species from the Brazilian Cerrado. Because of their thick bark, none of the trees analyzed were top-killed after a severe fire event. The structural and functional variations of the bark were also associated with water storage and transport, functions related to properties of the inner bark. In fact, species with a thicker and less dense inner bark were the ones that had the highest water contents in the wood, bark, and leaves. Lower bark density was also related to higher stem hydraulic conductivity, carbon assimilation, and growth. Overall, we provide strong evidence that in addition to protection from fire, the relative investment in bark also reflects different strategies of water use and conservation among many Cerrado tree species.
The objective of this study was to evaluate the performance of hybrid maize inoculated with Azospirillum brasilense under different levels of topdressing nitrogen. The experiment was conducted under field conditions in the conventional tillage system, in the experimental station of the Federal Institute Goiano (Rio Verde, GO), in the 2012 crop season. The parameters evaluated were: ear mass; cob mass; ear length, ear diameter, ear grain weight and total weight per plot. The experimental design was randomized blocks with four replications. The treatments were arranged in a factorial arrangement 1 x 2 x 5, with one hybrid (DKB 390 YG RR2), absence and presence of inoculation with A. brasilense and five doses of N (0, 25, 50, 75 and 100%) totaling 40 plots and 640 m2. The experimental data were subjected to analysis of variance by test F, and when significant the means were compared by Tukey test at 5% probability. The optimal dose of nitrogen applied at top dress in the maize inoculated was approximately 89% of the recommended dose, which may range up to 84% without significant loss in yield or in the effect of A. brasilense.
A uniformidade de distribuição da água em áreas irrigadas influencia diretamente o manejo, a qualidade, a eficiência e o custo da irrigação, assim como o desempenho da cultura no campo. Deste modo, objetivou-se avaliar a uniformidade de distribuição da água ao longo do tempo em um sistema de gotejamento subsuperficial. O experimento foi conduzido em bancada de ensaios instalada em casa de vegetação na área experimental do IFGoiano-Câmpus Rio Verde. Sobre uma bancada de ensaios foram instalados 20 recipientes de PVC com 0,1 m de diâmetro e 0,6 m de altura, contendo cada recipiente um gotejador. Utilizou-se solo de textura argilosa para preencher os recipientes. O delineamento experimental foi inteiramente casualizado, utilizando-se dois modelos de gotejadores, com 20 repetições (gotejadores). Utilizou-se a pressão de 1,0 bar (modelo 1 e 2). Os valores de Coeficiente de Uniformidade de Christiansen e Coeficiente de Uniformidade de Distribuição diminuem ao longo do período de operação enquanto que os valores de Coeficiente de Variação de Vazão crescem, conforme ocorre o aumento do tempo de funcionamento. Palavras chave: Vazão, uniformidade, tempo de funcionamento.
RESUMOO crescimento da cana-de-açúcar (Saccharum officinarum L.) pode ser afetado pela interferência de diversos fatores, dentre eles a disponibilidade hídrica e de nitrogênio. Deste modo, objetivou-se avaliar a influência da adubação nitrogenada, aplicada via sistema de irrigação por gotejamento subsuperficial, sobre o crescimento da cana-planta cultivada sob irrigação plena ao longo do ciclo. O experimento foi instalado em condições de campo na área experimental do IFGoiano -Câmpus Rio Verde, GO. O delineamento experimental utilizado foi o de blocos casualizados, analisado em esquema de parcela subdivida, com quatro repetições. Os fatores avaliados nas parcelas foram a aplicação de nitrogênio, nas doses de 0 e 100 kg ha -1 na forma de ureia, enquanto as subparcelas consistiram em nove épocas de avaliação (90, 120, 150, 180, 210, 240, 270, 300 e 330 dias após o plantio -DAP), sendo que para número de colmos foram utilizadas cinco épocas de avaliação (210, 240, 270, 300 e 330 DAP), assim como para número de perfilhos e número de plantas (90, 105, 120, 135 e 150 DAP). Foram avaliados: altura de planta, diâmetro de colmo, número de colmos, comprimento de folha, número de folhas, área foliar, número de perfilhos e número de plantas. Observou-se que não houve interferência da adubação nitrogenada para nenhum dos parâmetros de crescimento da cana-de-açúcar analisados. As alterações morfológicas observadas na cana-de-açúcar ocorreram em função do ciclo da cultura.Palavras-Chave: fertirrigação, adubação nitrogenada, biometria.
Drought is the most harmful environmental factor crop productivity. Some chemicals are used in agriculture to mitigate the damage from this stress on plants. Therefore, we examined whether the spraying of zinc sulfate (ZS), potassium phosphite (KPhi) and the hydrogen sulfide (H2S) donor sodium hydrosulfide (NaHS) would mitigate the deleterious effects of water deficit on sunflower plants by analyzing physiological and biometric characteristics. The experiment was carried out in a greenhouse using a randomized block design with five replications. The treatments were arranged in a 4 x 2 factorial scheme: [Factor A (Alleviators)] - spraying of KPhi (0.5 L ha-1), ZS (3.2 kg ha-1), NaHS (1.2 g ha-1), and water; [Factor B (substrate humidity, SH)] - 100% (well irrigated) and 30% (water deficit, WD) of field capacity. Under WD conditions, alleviators led to the maintenance of higher values of water potential (ΨW), a lower content of leaf malonaldehyde (MDA), and increased activity of the antioxidant enzyme peroxidase (POX), except for ZS. However, leaf osmotic potential, proline concentration, variables related to gas exchange and chlorophyll a fluorescence, and biometric characteristics differed only according to the SH factor. The results of ΨW and MDA for sunflower plants under WD are indicative of the mitigating capacity of ZS, KPhi, and H2S. Thus, the spraying of these compounds on sunflower plants mitigates the effects of WD, acting specifically in physiological processes related to antioxidant responses and in the maintenance of water in leaf tissues.
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