-Evaluation of root morphology and kinetic parameters assist in the characterization of genotypes in nutrient uptake efficiency. This study characterized Australian cedar clones concerning their nutrient uptake capacity at the seedling stage through root morphology and the kinetics of P, K, Ca, and Mg uptake. The experiment was conducted using a nutrient solution in a greenhouse and growth chamber. Four Australian cedar clones (HE, XF, XD, and XE), provided by Bela Forest View (Empresa Florestal Bela Vista), were tested using a completely randomized design with five repetitions, totaling 20 experimental plots. The length, volume, surface area, average diameter, and root length per diameter class, as well as the uptake parameters V max , K m , C min , and the estimated inflow of P, K, Ca, and Mg, were determined. The root morphological characteristics varied between Australian cedar clones; clone XD exhibited the largest root system development. The uptake efficiency of P, K, Ca, and Mg varied between cedar Australian clones. When availability differed, clones XE and XF exhibited greater plasticity in the uptake of P and K respectively, and similar results were found for clone HE in the uptake of Ca and Mg.Keywords: Morphological attributes of root systems. Kinetic parameters. Inflow of P, K, Ca, and Mg. Nutrient uptake. Toona ciliata. MORFOLOGIA RADICULAR E CINÉTICA DE ABSORÇÃO DE NUTRIENTES POR CLONES DECEDRO-AUSTRALIANO RESUMO -Avaliações da morfologia radicular e de parâmetros cinéticos auxiliam na caracterização de genótipos quanto à eficiência de absorção de nutrientes. O objetivo deste trabalho foi caracterizar clones de cedro-australiano quanto à capacidade de absorção de nutrientes na fase de muda, por meio da determinação de características morfológicas radiculares e dos parâmetros cinéticos de absorção de P, K, Ca e Mg. O experimento foi conduzido em solução nutritiva em casa de vegetação e câmara de crescimento. Foram testados quatro clones de cedro-australiano (HE, XF, XD e XE), provenientes da empresa Bela Vista Florestal, sendo utilizado o delineamento inteiramente casualizado com cinco repetições, totalizando em vinte parcelas experimentais. Determinou-se o comprimento, volume, área superficial, diâmetro médio e extensão de raízes por classes de diâmetro, bem como os parâmetros de absorção Vmax, Km, Cmin e o influxo estimado para P, K, Ca e Mg. As características morfológicas radiculares variam entre os clones de cedro-australiano, tendo destaque para o clone XD que apresentou um maior desenvolvimento do sistema radicular. A eficiência de absorção de P, K, Ca e Mg varia entre os clones de cedro-australiano. Em condições de variações na disponibilidade, os clones XF e XE apresentam maior plasticidade na absorção de P e K, respectivamente, e o clone HE na absorção de Ca e Mg. Palavras-chave:Atributos morfológicos do sistema radicular. Parâmetros cinéticos. Influxos de P, K, Ca e Mg.Absorção de nutrientes. Toona ciliata.
The Australian Red Cedar presents a great exploitation potential in Brazil, but works about the nutrient requirements and deficiency characterization in that species are still scarce. The objectives of this work were evaluating the effects of the omission of micronutrients and characterizing the nutrient deficiency symptoms in Australian Red Cedar saplings. The experiment was conducted in a greenhouse for a 90-day period. Australian Red Cedar cuttings were cultivated in pots with a nutrient solution under the missing element technique. The omission of the micronutrients B, Cu, Fe, Mn, and Zn affect negatively the height, diameter, and dry matter yield of the Australian Red Cedar plants. The micronutrient which affected the relative growth of the plants the most was B. Australian Red Cedar plants deficient in micronutrients present several visual symptoms characteristic of the metabolism disorders. The perception of the deficiencies through the visual diagnosis can be useful in the nutrient management of the culture of the Australian Red Cedar.
Forest species present around 75% of their nutrient demand in the initial growth stage. The objectives of this study were: to determine appropriate doses of N, P and K to be applied for Australian cedar cultivation in Oxisols; and to establish foliar contents suitable for the initial stage of plant development. Three concomitant experiments were carried out using randomized blocks design with four replications. In the first, it was provided 5 doses of N, and in the second 5 doses of P2O5, and in the third 5 doses of K2O. In all three experiments, Australian cedar seedlings were planted at 3x2 m spacing. Maximum economic yield (MEY) was achieved when was provided 75 g N, and 80 g P2O5 per planting hole. In this study, could not be established the dose of K2O that allows MEY, because there was no difference in height and diameter of plants as a function of potassium fertilizer rates. The initial K concentration in the soil (around 100 mg.dm-3) seems adequate to meet the nutritional needs to Australian cedar seedlings. Foliar concentrations did not vary with levels of N, P2O5 and K2O applied to soil. Mean content of N, P and K in the leaves of Australian cedar seedlings were 30, 18 and 2 mg.kg-1, respectively.ResumoSugestões de adubação nitrogenada, potássica e fosfatada para o cedro-australiano em Latossolos. Espécies florestais apresentam cerca de 75% de sua demanda de nutrientes na fase inicial de crescimento. Os objetivos deste estudo foram determinar doses adequadas de N, P e K a serem aplicadas para o cultivo de cedro-australiano em Latossolos e estabelecer os teores foliares adequados para a fase inicial de desenvolvimento da planta. Foram realizados três experimentos concomitantes, em que se aplicaram cinco doses de N no primeiro, cinco doses de P2O5 no segundo e cinco doses de K2O no terceiro. As mudas foram plantadas no espaçamento de 3 x 2 m, no delineamento experimental em blocos casualizados, com quatro repetições. A máxima eficiência econômica (MEY) foi alcançada com a oferta de 75 g de N e 80 g de P2O5 por cova de plantio. Para potássio, não foi possível estabelecer a dose que permite MEY, porque não houve diferença de altura e diâmetro das plantas que receberam doses diferentes do elemento. Portanto, a concentração inicial de K no solo (cerca de 100 mg.dm-3) parece ser adequada para satisfazer as necessidades nutricionais da espécie. O teor dos nutrientes nas folhas não variou com os níveis de N, P2O5 e K2O aplicados no solo, e os níveis médios de N, P e K nas folhas de cedro-australiano foram de 30, 18 e 2 mg.kg-1, respectivamente.Palavras-chave: Nutrição mineral; silvicultura; Toona ciliata.
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