increase of Al leaf content as a function of Al concentration in the nutrient solution. Plants grown in 1 mM Al showed a remarkable increase of K leaf content, net photosynthesis, stomatal conductance, and transpiration, while in 4 mM Al there were reductions of N, P, and K contents, gas exchange characteristics, and height. H. impetiginosus did not have mechanisms of avoidance, compartmentalization, or resistance to high Al concentrations. Indeed, this species showed a hormetic response, with low Al concentrations stimulating and high Al concentrations inhibiting plant responses.
The heterogeneous light pattern in forest environments leads to specific morphological and physiological responses. However, anthropogenic pressures in areas such as Atlantic Forest and Cerrado are modifying the light availability, and consequently the forest community composition. The aim of this study was to investigate the plasticity of forest species Pimenta pseudocaryophyllus under full sunlight and shade conditions. P. pseudocaryophyllus showed typical shade plant phenotype, with higher net photosynthesis, transpiration, and chlorophyll a and b contents when cultivated under this condition. The decrease in net photosynthesis under full sunlight conditions is probably related to PSII photoinhibition. In addition, under full sunlight, reduced height, number of leaves, and specific leaf area was observed, while plants in shade increased these characteristics. P. pseudocaryophyllus did not show high morphological and physiological plasticity, which may be a maladaptive response. It was concluded that forest disturbances could compromise the occurrence and survival of P. pseudocaryophyllus.
The distance effect of the edge and two matrices (pasture and sugar cane) on the microclimate and anatomical and physiological properties of Psychotria vellosiana leaves were studied in two semideciduous forest fragments in southern Minas Gerais. The plots were set at distances (0, 20, 40, 60 and 80 m) from the edge to the interior of each fragment: 0, 20 and 40 m distances were considered edge, whereas 60 and 80 m were considered interior. Microclimate data were collected in all plots and radiation data and canopy openness at 0, 40 and 80 m. Leaves were collected for analysis of their chlorophyll content and anatomical properties. No differences were found for the canopy openness and radiation between the edge and interior of the fragments. The temperature and humidity data and the soil humidity displayed no differences within or between each fragment. Only the soil temperature data differed between the fragments. The leaves displayed the same chlorophyll content for the edge and interior of the fragments and between the fragments. These results may be related to the microclimate properties found along the 80 m transect in each fragment. Some anatomical data suggested a better adaptation of P. vellosiana to the fragment surrounded by the pasture matrix. However, we require a more detailed analysis that includes nutrient information and water availability from the soil. RESUMO: O efeito da distância da borda e de duas matrizes (pastagem e cana-de-açúcar) sobre o microclima e as características anatômicas e fisiológicas de folhas de Psychotria vellosiana foi estudado em dois fragmentos de floresta estacional semidecidual no sul de Minas Gerais. As parcelas foram estabelecidas em distâncias-0, 20, 40, 60 e 80 m-a partir da borda para o interior de cada fragmento. As distâncias de 0, 20 e 40 m foram consideradas como borda e de 60 e 80 m, como interior. Em todas as parcelas, foram coletados dados microclimáticos e, nas parcelas de 0, 40 e 80 m, dados de radiação e abertura de dossel. Folhas foram coletadas para análises de teor de clorofila e características anatômicas. Não houve diferença em relação à abertura do dossel e à radiação entre borda e interior de fragmentos. Os dados de temperatura e umidade do ar, e umidade do solo não apresentaram diferenças dentro dos fragmentos e entre estes. Somente os dados de temperatura do solo variaram entre os fragmentos. As folhas apresentaram o mesmo teor de clorofila para borda e interior de fragmentos, e entre os fragmentos. Estes resultados podem estar relacionados às características microclimáticas encontradas ao longo dos 80 m em cada fragmento. Alguns dados anatômicos sugerem melhor adaptação de P. vellosiana no fragmento circundado por matriz de pasto. No entanto, é necessária uma análise mais detalhada, incluindo a disponibilidade de água e nutrientes do solo. Leaf anatomy and chlorophyll content in Psychotria vellosiana Benth influenced by the edge and two matrices Anatomia foliar e teor de clorofila em Psychotria vellosiana Benth influenciados pela matriz e pela di...
The degradation of Cerrado biome has been increasing the demand for high quality tree seedlings, so that it is necessary to understand the nutritional requirements of these plants. Hymenaea courbaril L., known as jatobá, has a wide distribution that makes it an alternative of reforestation of degraded areas. The aim of the experiment was to evaluate H. courbaril initial growth and gas exchange characteristics under different potassium concentrations (K+). The experiment was arranged in a completely randomized design with five treatments (T0- 0, T1- 3, T2- 6, T3-9 e T4- 12 mM of K+) and four repetitions. Growth measurements were carried out every 15 days. SPAD index and gas exchange measurements were evaluated at 0, 30, and 60 days after treatment imposition. At the end of the experimental period, dry matter was evaluated, and root: shoot ratio (R:S) and Dickson quality index (DQI) were calculated The data were subjected to a one-way ANOVA and by Tukey’s test (P<0.05). The growth characteristics did not show significant difference with different concentrations of K+. At 0 and 30 days the photosynthetic traits were not different. However, at 60 days the absent- (T0), lower- (T1), and hyper- (T4) K+ concentration showed a reduction in SPAD index and gas exchanges parameters, confirming the role of this nutrient in the photosynthetic activity. Thus, regardless the K+ doses during 60 days, H. courbaril reached the growth requirements of field plantations. However, after this period the plant survival could be decreased in low K+ availability conditions.
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