A competição com plantas daninhas por água ou luz pode afetar parâmetros fisiológicos das culturas de interesse. A partir desse estudo, objetivou-se avaliar o efeito da umidade do solo e a competição de duas espécies de plantas daninhas em diferentes combinações nas características fisiológicas de plantas de eucalipto. O delineamento experimental utilizado foi ao acaso com quatro repetições em esquema fatorial 4 x 4. O primeiro fator correspondeu às combinações de plantas do híbrido clonal de eucalipto cultivadas em competição com picão-preto e braquiária: 1 - Uma planta de eucalipto + duas plantas de braquiária por vaso; 2 - Uma planta de eucalipto + duas de picão-preto por vaso; 3 - Uma planta de eucalipto + uma planta de picão-preto + uma planta de braquiária por vaso, e; 4 - uma planta de eucalipto por vaso. O segundo correspondeu aos níveis de água no solo: 100, 74, 67 e 60% da capacidade de campo. Foram feitas avaliações dos teores de clorofila a, b, a/b e total, bem como, variáveis relacionadas a fluorescência da clorofila. O eucalipto crescendo isoladamente mostrou maiores valores de clorofila a clorofila b e clorofila total. A relação clorofila a/ b foi inferior em todos os níveis de umidade do solo. A fluorescência inicial mostrou tendência de decréscimo com o aumento da umidade. Nas menores umidades testadas as plantas de eucalipto se encontravam em condição de estresse com valores de fluorescência variável/fluorescência máxima inferiores a 0,75.
Brassica napus, a versatile crop with significant socioeconomic importance, serves as a valuable source of nutrition for humans and animals while also being utilized in biodiesel production. The expansion potential of B. napus is profoundly influenced by climatic variations, yet there remains a scarcity of studies investigating the correlation between climatic factors and its distribution. This research employs CLIMEX to identify the current and future ecological niches of B. napus under the RCP 8.5 emission scenario, utilizing the Access 1.0 and CNRM-CM5 models for the time frame of 2040–2059. Additionally, a sensitivity analysis of parameters was conducted to determine the primary climatic factors affecting B. napus distribution and model responsiveness. The simulated outcomes demonstrate a satisfactory alignment with the known current distribution of B. napus, with 98% of occurrence records classified as having medium to high climatic suitability. However, the species displays high sensitivity to thermal parameters, thereby suggesting that temperature increases could trigger shifts in suitable and unsuitable areas for B. napus, impacting regions such as Canada, China, Brazil, and the United States.
Invasive macrophytes are considered problematic in natural environments and hydroelectric reservoirs. Climate changes, the occurrence of watercourses, and biotic interactions influence the biological invasion of macrophytes. Native species can correlate with invasives positively or negatively. Urochloa subquadripara is an invasive in natural or disturbed habitats co-occurring with the natives Eichhornia crassipes and Salvinia minima. Aquatic plant communities can be altered by climate change, so species distribution models (SDMs) are important tools for predicting in-vaded areas. This work aimed to make an SDM for U. subquadripara correlating with the poten-tial distribution of native species E. crassipes and S. minima. Occurrence data for U. subquadripara, E. crassipes, and S. minima were collected from databases and in consultation with the published literature. Parameters encompassing biological information of the species were entered into the CLIMEX software and used to generate the Ecoclimatic Index (EI). The species co-occurrence was performed based on multicriteria decision-making (MCDM), and weights were assigned using the analytical hierarchy process (AHP). It was observed that U. subquadripara, E. crassipes, and S. minima have a higher occurrence in tropical and subtropical regions; however, it is predicted that, from climatic changes, these species may move to high latitudes. According to climate change, the risk of invasion by U. subquadripara in the northern hemisphere is mainly in lakes, while in the southern hemisphere, the areas conducive to invasions are rivers and reservoirs. In general, emerging and floating macrophyte species such as U. subquadripara, E. crassipes, and S. minima will be favored, causing suppression of submerged species. Therefore, identifying the potential distribution of these species allows the creation of pre-invasion intervention strategies.
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