Resumo O objetivo deste trabalho foi estabelecer um protocolo eficiente para a organogênese in vitro de Dalbergia nigra. Para isso, plântulas com 30 dias de idade foram seccionadas em seus nós cotiledonares e segmentos nodais. Esses materiais foram cultivados em meio com diferentes combinações das citocininas 6-benzilaminopurina e tidiazuron. Após 60 dias em sala de crescimento mantida a 27°C e submetida a fotoperíodo de 16 horas, foram analisadas as características de crescimento. Explantes dos nós cotiledonares apresentam maior potencial morfogenético, independentemente da adição de citocininas. Nós cotiledonares em meio suplementado com 2.22 µmol L-1 de BAP são a melhor combinação para a propagação in vitro de D. nigra.

Abstract The objective of this work was to establish an efficient protocol for the in vitro organogenesis of Dalbergia nigra. For this purpose, 30-day-old seedlings were sectioned at their cotyledonary nodes and nodal segments. These materials were cultivated in a medium with different combinations of the 6-benzylaminopurine and thidiazuron cytokinins. After 60 days in a growth chamber set at 27°C and a 16-hour photoperiod, growth characteristics were analyzed. Explants from the cotyledonary nodes show a greater morphogenetic potential, regardless of the addition of cytokinins. Cotyledonary nodes in the medium supplemented with 2.22 µmol L-1 BAP show the best combination for the in vitro propagation of D. nigra.

ABSTRACT Melanoxylon brauna is propagated by seeds, however, low yield, pest attack and short viability are problems in seedling production. In vitro cultivation is an alternative for large-scale seedling production, but studies with this species are scarce. The aim of the work was to analyze the in vitro morphogenesis of braúna. Explants after induction of growth regulators. Three experiments were performed: I. In vitro bud proliferation of juvenile explants at different BAP concentrations. Was analyzed the number and length of shoots (mm); bud explants-1 (%); calogenesis (%) and direct and indirect organogenesis budding-1 (%). II. In vitro rhizogenesis of shoots with different types and auxin concentrations. III. In vitro rhizogenesis of under temporary immersion of shoots at different IBA concentrations. It was analyzed in experiment I and II: calogenesis (%); rhizogenesis (%); number, length (mm) and root dry mass (mg) the shoots. The nodal segment with two axillary buds was the most responsive explant regardless of the use of BAP. The stem apex with the use of BAP (2.5-3.5 mg.L-1) was the most responsive in the proliferation of shoots. Tested concentrations of auxins IBA, NAA and 2,4-D were not sufficient for in vitro rhizogenesis. The average of the maximum technical efficiencies of the variables used to analyze rhizogenic process suggests the treatment of the shoots base by temporary immersion in the IBA at an approximate concentration of 2,500 mg.L-1 and planting on the vermiculite substrate.

ABSTRACT The development of tissue cultured-based protocols applied to braúna, an endangeres species, would be though highly desirable. However, contamination-free explants are determinant for the success of this technique, which might be vulnerable to the toxicity of disinfectants. Here, we aimed at establishing an efficient protocol for in vitro production of axenic seedlings of braúna and to evaluate the toxicity of disinfectant agents in the Lactuca sativa model species. Experiments I and II: Seeds were treated with sodium hypochlorite (NaOCl) and fungicide captan, with and without residue, by different immersion times, respectively. The following were analyzed: contamination; germination and normal and abnormal seedlings. Experiment III: Lettuce seeds placed in Petri dishes were exposed to 2.5 mL captan at 0.5; 1; 2; 4 and 8%; 0.01% glyphosate and distilled water. The germination, length of seedlings, cell cycle, nuclear and chromosomal alterations of the cells of the root meristem were assesed. The isolated use of NaOCl was not efficient in the disinfestation of braúna seeds. However, the immersion of the seeds in captan, for 10 minutes with its residue, led to higher germination and vigor indexes; however, resulted in the formation of abnormal seedlings. This compound exhibited toxicity in the lettuce model seeds because affected the germination and the whole development of the seedlings, showing clastogenic and aneugenic action in the meristematic cell cycle.

A revisão relata os principais benefícios do plantio misto de eucalipto com leguminosas arbóreas fixadoras de nitrogênio atmosférico. Buscou-se analisar as interações ecológicas das espécies envolvidas no sistema, a arquitetura espacial utilizada e o possível aumento de produtividade do sistema consorciado. Com base nisso, observa-se que o cultivo misto de eucaliptos com leguminosas arbóreas fixadoras de nitrogênio atmosférico só deve ser realizado em locais onde os processos e as interações entre espécies aumentarão o crescimento, a produção de biomassa ou a qualidade do produto final desejado. De forma geral, os estudos indicam que o interplantio de leguminosas arbóreas fixadoras de nitrogênio proporciona incremento na produtividade das plantas de eucalipto. Contudo, devem-se analisar as interações dos plantios mistos até a sua idade de rotação, para que, com isso, possam ser verificados os possíveis efeitos da fixação biológica de nitrogênio atmosférico pela leguminosa na produtividade do eucalipto.

In this paper, we aimed to review the main benefits of the mixed plantation of eucalyptus with nitrogen-fixing legume trees. To this end, the ecological interactions of the species involved in the system was analyzed, as well as the space architecture used and the possible increase in productivity caused by the intercropping. On this basis, it was possible to observe that the mixed cropping of eucalyptus with nitrogen-fixing legume trees should be implemented only in locations where the processes and interactions between species will increase the growth, biomass production or quality of desired product. In general, studies indicate that mixed plantation provides an increase in productivity in eucalyptus stand. However, it is important to analyze the interactions of mixed stand until the age of rotation, so that the possible effects of atmospheric nitrogen fixation by legume trees on the productivity of eucalyptus can be verified.

RESUMO Este trabalho teve por objetivo estudar as concentrações e a redistribuição de nutrientes minerais nas folhas recém maduras e no folhedo em um povoamento de Acacia mearnsii De Wild, com 3 anos de idade, plantado em solos de baixa fertilidade, no Estado do Rio Grande do Sul. Dentre os elementos minerais analisados o N foi o que teve maior concentração tanto nas folhas récem maduras como no folhedo. O fósforo e o potássio foram os nutrientes que mais retranslocaram. No entanto, o cálcio foi o elemento que teve uma menor retranslocação.

ABSTRACT This work aimed to study the concentration and the redistribution of mineral nutrients in the newly mature leaves and in the litter, in a three years old Acacia mearnsii De Wild. forest, planted in soils with low fertility in Rio Grande do Sul State. Among the mineral elements analysed nitrogen had higher concentration in the newly mature leaves as well in the litter. Phosphorus and potassium were the nutrients more retranslocated. However, calcium was the element that presents had the smaller retranslocation.