This aim of this work was to evaluate the initial growth of Cordia trichotoma seedlings, submitted to different sizes of recipients and doses of controlled-release fertilizer (CRF). This experiment was performed in a greenhouse, and evaluation was done in factorial scheme using two volumes of recipients (110 and 180 cm3) combined with five doses of CRF (0 (controlled); 2.5; 5.0 and 7.5 g L-1 de substrate). The experimental design was completely random with four repetitions each evaluated in factorial scheme. Significant interaction was observed between the size of the recipient and the doses of CRF for most analyzed variables. It indicated that, the quantity of fertilizer to be used depends on the size of the recipient, emphasizing that in the conditions in which the seedlings were produced; the minor volume of substrate does not cause restrictions on growth. It is perceived that most evaluated parameters need higher doses than the maximum provided, in at least one of the recipients, demonstrating elevated nutritional requirement of the species during the nursery phase. The recipient of 110 cm³, combined with the dose of 7.5 g L-1 of CRF is recommended because of the economy of substrate, nursery space and practicality of transportation. Key words: Native species, controlled-release fertilizer, louro-pardo, seedling production.

O objetivo do estudo foi avaliar se a presença do hidrogel afeta as propriedades físicas e químicas do substrato e a relação do hidrogel com doses de adubação no desenvolvimento de mudas. No substrato com presença e ausência do hidrogel foi realizada análise de características químicas e físicas. A produção de mudas foi conduzida em casa de vegetação sob irrigação reduzida, utilizando delineamento inteiramente casualizado em arranjo bifatorial 2 x 6, em que os níveis do fator “A” referiram-se a presença (6 g L-1) ou ausência do hidrogel e os níveis do fator “B”, às doses do fertilizante de liberação controlada – FLC (0; 25; 50; 75; 100 e 125% da dose usual). Após 90 dias de semeadura foi realizada a avaliação de parâmetros morfológicos das mudas. O uso do hidrogel apresentou melhoria das características físicas e químicas do substrato, principalmente aos atributos que envolvem retenção e disponibilização de água às plantas. Com a adição do hidrogel e aproximadamente 50-75% da adubação convencional, houve aumento da altura, diâmetro de coleto, massa seca radicular e total, além do índice de qualidade de Dickson. Com o uso do hidrogel e adubação superior a 100% há redução do crescimento das mudas. Já, sem a adição do polímero, o melhor desempenho das mudas é obtido com doses superiores a 100% da adubação convencional. Em geral, o uso do polímero permite a redução em, pelo menos, 25% da adubação convencional (6 g L-1), podendo ser reduzida em até 50%.

Handroanthus heptaphyllus is a tree species with wood of high economic value, used in the manufacture of furniture and civil construction. When grown in soils with low availability of natural nitrogen (N), it demonstrates low growth potential. Thus, the study aimed to define the growth and physiological responses in H. heptaphyllus plants subjeted to N fertilization after planting. Five rates of N (0, 45, 90, 180 and 270 kg N ha⁻¹) were tested at three vegetative phases of the plants (6, 12 and 18 months after planting). At each age, the height, stem diameter, concentration of N and photosynthetic pigments in leaves, chlorophyll a fluorescence and total N content in soil and tissue were determined. The addition of N increased total N content in the soil and the leaves, the concentration of photosynthetic pigments, the use of light energy and the maximum quantum yield of photosystem II, resulting in greater plant growth. In the period between the 6^th and the 18^th month after planting, the plants showed an increase of 135 cm in height. The concentrations of N and photosynthetic pigments in the leaves decreased over time, because of the effect of dilution and remobilization of N. The use of 260.0 kg N ha⁻¹kg divided in 35% of the dose added in small holes in the soil at planting; 32.5% three months after the first application; and the remainder in the sixth month after planting increased growth in height and stem diameter at 18 months after planting.

The increase in the availability of phosphorus (P) can reduce the toxicity of copper (Cu) to plants because it favors the formation of complexes and precipitates, reducing the bioavailability of this metal. The objective of this study was to investigate the capacity of P supplementation to decrease the phytotoxicity of excess Cu in the growth and in physiological parameters of wheat plants. Plants of wheat (Triticum aestivum L.) were cultivated on sand substrate and, for 30 days, submitted to the control treatments - Hoagland & Arnon solution 100% (H&A); H&A + 47 mg P L⁻¹ (H&A + P); H&A + 28 Cu mg L⁻¹ (H&A + Cu); H&A + 47 mg P L⁻¹ + 28 mg Cu L⁻¹ (H&A + P + Cu). Plant growth, tissue nutrient concentration, photosynthetic pigment concentration, chlorophyll a fluorescence and superoxide dismutase enzyme activity in the leaves were evaluated. We observed that the treatments H&A + P and H&A + Cu provided higher height, while H&A + P + Cu provided higher dry matter yield of shoots and roots in plants. A higher Cu content in the leaves was observed in the plants cultivated with addition of 28 mg Cu L⁻¹, however the application of Cu did not cause loss of photochemical energy and energy dissipation in the PSII antenna complex. The addition of 47 mg P L⁻¹ provided a higher rate of electron transport in wheat plants. Therefore, wheat plants were tolerant to increasing the concentration of Cu in the culture medium and the addition of P attenuated the toxic effects caused by Cu, mainly in the roots of plants.