Brazil is the largest producer, consumer and exporter of seeds of forage species, thus the adoption of new technologies for expansion and maintenance of this market is of great

The symptoms of magnesium (Mg) deficiency have been well documented in crop plants. The relationship between Mg deficiency as an important abiotic stress factor and the sugar partitioning may restrict the root growth and limit the success of planting in the field. Despite of this, the primary physiological effects of low Mg availability remain largely unknown in eucalyptus. This paper aimed to investigate how the Mg deficiency affects biochemical aspects of sugar partitioning associated to dry matter accumulation in roots of Eucalyptus urophylla young plants, clone AEC 144. Experimental work was carried out in a greenhouse, arranged by completely randomized design, consisted by split plot 5x4, using the following Mg levels: 0, 25, 50, 75 and 100% in the Mg concentration of Clark's nutrient solution. Evaluations were performed at 15, 30, 50 and 120 days after seedlings planting (DAP) in pots. Soluble (SS) and reducing (RS) sugar contents, invertase and sucrose synthase (susy) activity and shoot and root dry matter were measured. Increased sugar concentrations, both SS and RS, were found in leaf tissues from 30 DAP. In root tissues, neither RS nor SS content showed differences between Mg deficiency treatments and control. Significant differences were also not found in both root dry matter accumulation and shoot/root dry matter ratio. The Mg deficiency did not affect sucrose cleaving in roots, which was predominantly catalyzed by acidic invertase, followed by susy and neutral invertase. We concluded that Eucalyptus urophylla is tolerant to Mg deficiency, because the sugar accumulation in the leaf tissues was not enough to constrain the dry matter accumulation in roots. ResumoOs sintomas da deficiência de magnésio (Mg) têm sido bem documentados em plantas cultivadas. A relação entre a deficiência de Mg, como um importante fator de estresse abiótico, e a partição do açúcares, pode restringir o crescimento das raízes e limitar o sucesso do plantio no campo. Apesar disso, os efeitos fisiológicos primários da baixa disponibilidade de Mg permanecem amplamente desconhecidos no eucalipto. Este trabalho buscou investigar como a deficiência de Mg afeta aspectos bioquímicos da partição de açúcares, associados ao acúmulo de matéria seca em raízes de plantas jovens de Eucalyptus urophylla. O experimento foi conduzido em casa de vegetação em delineamento inteiramente casualizado, com parcelas subdivididas 5 x 4, utilizando os seguintes níveis de Mg: 0, 25, 50, 75 e 100% na concentração da solução nutritiva de Clark. As avaliações foram realizadas aos 15, 30, 50 e 120 dias após o plantio (DAP) das mudas em vasos. Determinaram-se os teores de açúcares solúveis (SS) e redutores (RS), as atividades da invertase e da sacarose sintase (susy), e a matéria seca da parte aérea e da raiz. Aumentos nas concentrações de açúcares, tanto SS como RS, foram encontrados em tecidos foliares a partir de 30 DAP. Nos tecidos de raízes, os teores de RS e SS não apresentaram diferenças entre os tratamentos com deficiência de Mg e o controle. Diferenças...

Root system characteristics were studied in order to evaluate the performance of eucalyptus clones in edaphoclimatic conditions of Vitória da Conquista, Bahia, Brazil. Two experiments were carried out. First, in a nursery, seedlings had their roots pruned and were planted in transparent tubes, outlined in quadrants, for evaluating root regeneration potential (RRP) and the dry matter partitioning from shoot to roots. 30 days after planting, AEC 144 and CO 520 were the clones with highest RRP, although CO 520 is similar to the other three clones. AEC 144 showed a tendency of better performance in dry matter partitioning from shoot to roots. The second experiment was carried out in the field. Six months after planting, plant height, stem diameter, leaf area, number of leaves, main root length, shoot and root dry matter, and soluble sugar, reducing sugar, protein and amino acid contents in roots were determined. There were no significant differences in all characteristics evaluated among the clones. Despite the differences related to RRP and dry mass partitioning, we concluded that the clones have characteristics which lead to a similar plant performance in the field, in the edaphoclimatic conditions of Vitória da Conquista.

Biostimulants consist of a mixture of growth regulators that, when they are sprayed on plants, act on hormonal balance, enhancing its development. Stimulate® is a biostimulant composed by indole butyric acid (0.005%), kinetin (0.009%) and gibberellic acid (0.005%) which promotes root growth, improves water and nutrients uptake, and helps restore plant hormonal balance. This research was based on the hypothesis that Stimulate® spraying can be an alternate way to mitigate negative effects of soil water-limiting on plant growth. The experimental work was performed in greenhouse and aimed to evaluate physiological responses of young plants of Eucalyptus urophylla sprayed with different Stimulate® concentrations and submitted to the following irrigation regimes: full, partial and no irrigation. Leaf water potential, relative water content, net photosynthesis, plant height and main root length were measured. Under water-limited conditions, plants sprayed with Stimulate® showed higher net photosynthesis and relative water content had a less decrease, due to osmotic adjustment. Spraying with Stimulate® also provided greater plant height and longer main root length in plants under water deficit. We conclude that the use of Stimulate® can be a viable option to mitigate negative water stress physiological effects in young plants of Eucalyptus urophylla, helping to partially maintain the plant growth under water-limited conditions.