RESUMO
Background: Leucaena leucocephala is a useful multipurpose tree species for agroforestry systems, but traditional seeded cultivars often become weedy and invasive. A seedless hybrid cultivar, 'KX4-Hawaii', offers a potential solution to this problem. However, relevant agronomic information and information on the performance of 'KX4-Hawaii' under varying growth conditions is required. The goal of this research was to evaluate 'KX4-Hawaii' as a source of agricultural biomass in Barbados, a small island developing state with limited arable land. Methods: 'KX4-Hawaii' air layers were imported into Barbados to create stock trees. Air layering was used to create propagation material and a field study was established with a 'KX4-Hawaii' hedgerow planted as a field border. Three plant spacings (50, 75, and 100 cm) were evaluated and data on the growth and biomass yields of the trees were collected at 4-month intervals. Precipitation data were used to investigate climatic effects on 'KX4-Hawaii' productivity. Results: 'KX4-Hawaii' was successfully propagated via air layers and could be planted directly in the field with irrigation. All recorded growth and biomass yields were correlated with precipitation. However, the woody (lignified stems and branches) biomass was more responsive to precipitation than the green (leaves and green tender stems) biomass and made up a large fraction of the total biomass produced. 'KX4-Hawaii' was productive even under drought conditions and biomass yields per meter of hedgerow increased with closer spacings. Of the tested spacing treatments, 75 cm was optimum for a 4-month pruning interval under the conditions seen in Barbados as it produced similar yields to the 50 cm spacing treatment but would require less propagation material.
Assuntos
Biomassa , Fabaceae/crescimento & desenvolvimento , Barbados , Agricultura/métodos , Árvores/crescimento & desenvolvimentoRESUMO
The bilateral intranigral infusion of 1 micromol 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in adult male Wistar rats caused a specific and partial loss of substantia nigra pars compacta (SNc) dopamine neurons, a partial depletion of striatal dopamine, and a deficit to learn the intra-maze cued version of the Morris water maze. Pre-training the SNc rats in the spatial version of the water maze or simply maintaining the animals on the water maze platform reversed this deficit. This improvement was even observed when the order of the extra-maze cues presented to the rats during pre-training of the spatial version was changed during training of the intra-maze cued version. However, this deficit was not reversed either by maintaining the animals on the platform if the spatial cues were surrounded and covered with a curtain or by swimming sessions in the maze without the escape platform and the curtain. These findings suggest that none of the following elements alone, learned during the spatial task pre-training, could help SNc rats learn the intra-maze cued task: improvement of swimming skills or knowledge of the existence of the escape platform; distance between the platform and the border of the pool; location of a particular extra-maze cue; relations among extra-maze cues. However, the simultaneous presence of the escape platform and extra-maze cues (irrespective of their relational configuration) during the pre-training sessions proved to be necessary for this improving effect to occur.