Linda Styer Caldas

Leaf functional traits of Neotropical savanna trees in relation to seasonal water deficit

The seasonal savannas (cerrados) of Central Brazil are characterized by a large diversity of evergreen and deciduous trees, which do not show a clear differentiation in terms of active rooting depth. Irrespective of the depth of the root system, expansion of new foliage in deciduous species occurs at the end of the dry season. In this study, we examined a suite of leaf traits related to C assimilation, water and nutrients (N, P) in five deciduous and six evergreen trees that were among the dominant families of cerrado vegetation. Maximum CO2 assimilation on a mass basis (Amass) was significantly correlated with leaf N and P, and specific leaf area (SLA; leaf area per unit of leaf mass). The highest leaf concentrations of both nutrients were measured in the newly mature leaves of deciduous species at the end of the dry period. The differences in terms of leaf N and P between evergreen and deciduous species decreased during the wet season. Deciduous species also invested less in the production of non-photosynthetic leaf tissues and produced leaves with higher SLA and maintained higher water use efficiency. Thus, deciduous species compensated for their shorter leaf payback period by maintaining higher potential payback capacity (higher values of Amass) and lower leaf construction costs (higher SLA). Their short leafless period and the capacity to flush by the end of the dry season may also contribute to offset the longer payback period of evergreen species, although it may involve the higher cost of maintaining a deep-root system or a tight control of plant water balance in the shallow-rooted ones.

Photosynthesis of mistletoes in relation to their hosts at various sites in tropical Brazil

Abstract Chlorophyll a fluorescence parameters showing the instantaneous performance and carbon-isotope ratios reflecting long-term behaviour of leaves were determined for a large number of mistletoe/host-pairs in the cerrado belt of Brazil. Study sites were a very exposed rupestrian field, a semi-exposed savanna and a highly shaded gallery forest. The major question asked was if photosynthetic capacity of mistletoe leaves differed from that of the leaves of their respective hosts. It is shown that except for the very exposed rupestrian field site, photosynthetic capacity appeared to be similar in mistletoes and host leaves. The superior behaviour of host leaves in the rupestrian field was due to particularly expressed sun-plant characteristics of the host. However, mistletoes always had higher average stomatal conductances, lower leaf temperatures at similar or even higher irradiance and higher intercellular CO2-partial pressures than hosts. Photosynthetic performance of mistletoe leaves was independent of whether a given mistletoe species parasitized aluminium-accumulating or non-accumulating host species in the cerrados with their aluminium-rich soils.

Seleção de matrizes e clones de mangabeira para o cultivo in vitro

High tax of mortality of mangabeira (Hancornia speciosa) seedlings in greenhouse conditions hinders its use on the reversion of the degradation of the natural vegetation, as well as on the preservation of the production and environmental integrity. The objective of this work was to select better mother plants and clones from sexual and assexual propagation, with potential to survive in vitro, for producing mangaba seedlings. Fruits were collected from 11 mother plants and from each plant, 24 seeds without aparent diseases were selected. After superficial desinfection, seeds were inoculated in MS medium without growth regulators and having a germination of 92.4% without significant difference between mother plants. On multiplication phase, with MS medium, with growth regulators BAP (6-benzilaminopurine) and IBA (indol-3-butiric acid), both at concentration of 1.28 mg L-1; the better mother plant was C1 and better clone was C1 15. During all phases of this work there was a high variability, mainly among clones. The selection must be made mainly among clones in mother plants.

Estiolamento e regeneração na multiplicação in vitro do abacaxizeiro híbrido PE x SC-52

receberam inoculo em tubos de ensaio contendo o meio de cultura MS e mantidosno escuro por 60 dias, para estiolamento. Foram utilizados trŒs tratamentos, sem reguladores de cresci-mento, ANA a 1,86€mg/L e AIA a 1,75€mg/L em cinco repeticies com dez explantes por repeticao. Naohouve diferenca no nœmero de brotos estiolados por explante entre os tratamentos avaliados. No€entanto,aos 35 dias de cultivo, os tratamentos com ANA e AIA apresentavam maior nœmero de nos por broto,sendo o ANA superior aos demais apos 60 dias. Brotos estiolados

Transgenic plants of ramie (Boehmeria nivea Gaud.) obtained by Agrobacterium mediated transformation

A regeneration and transformation protocol for ramie (Boehmeria nivea Gaud.) is presented. Regeneration was obtained from leaf discs placed on solid B-5 medium (Gamborg et al. 1968) containing adequate concentrations of auxin and cytokinin. Co-cultivation of leaf discs with Agrobacterium tumefaciens and subsequent regeneration resulted in transgenic plants as shown by Southern blot and analysis of expression of the GUS-marker gene.