Seed and seedling variation amongst provenances in Faidherbia albida

Seed and seedling morphology of Faidherbia albida was investigated in conjunction with isozyme analysis. Seeds from 19 seed lots representing central, western and southern parts of the distribution range were studied. The results are in accordance with the earlier discovery of two distinguishable ecogeographical races. The isozyme locus Sod-2 shows two different phenotypic patterns over the geographical range of the species. One phenotypic pattern was confined to the central arid western parts of the distribution range (the Sahelian range) and the other to the southern part of the range, although the two patterns were found to overlap in north-eastern Ethiopia. A similar bimodal pattern of variation was also shown in the seed and seedling morphology; one phenotype appears to be endemic to the southern part of the distribution range, whilst the other appears to be endemic to the Sahelian range. Clines of some morphological traits investigated were also evident in the riparian habitat of the central distribution range (the Nile (N)). Based on the results, recommendations pertaining to the utilisation of the species gene resources and stand establishment were inferred

2s(1/2) occupancies in Si-30, P-31, and S-32

Elastic electron scattering off Si-30 and P-31 was studied in an effective momentum-transfer range of 1.8-3.0 fm(-1). The form-factor data were analyzed together with existing data sets for these nuclei and for S-32 in a model-independent Fourier-Bessel expansion. For P-31 the M1 contribution was subtracted following an established parametrization. Results of Hartree-Fock (HF) calculations, performed for these three nuclei in a spherical basis and in an axially deformed basis, are compared to experiment. Occupancies have been determined which, when used in the spherical-basis HF calculations, lead to a good description of the elastic form-factor data. The deformed-basis calculations have been used to study the influence of the deformation on the calculated binding energies and ground-state charge densities. In all calculations the influence of using different effective nucleon-nucleon interactions was investigated. The resulting differences in 2s(1/2) in occupancy are combined with results from previous existing (e,e'p) experiments to yield ''absolute occupancies'' for the 2s(1/2) orbital. The deduced 2s(1/2) occupancies for Si-30 and S-32 are 0.24(4) and 1.35(19), respectively

Does geographic origin dictate ecological strategies in Acacia senegal (L.) Willd.?: evidence from carbon and nitrogen stable isotopes

Background and aims: Acacia senegal, a leguminous dryland tree, is economically and ecologically important to sub-Saharan Africa.Water-use efficiency (WUE) and biological nitrogen fixation (BNF) are fundamental to plant productivity and survival.We quantify provenance differences in WUE, BNF, photosynthesis, biomass and gum arabic production from A. senegal assessing genetic improvement potential. Methods: Using stable isotope ratios, we determined WUE (δ13C) and BNF (δ15N) from provenances of mature A. senegal in field-trials (Senegal), sampling leaves at the beginning (wet) and end (dry) of the rainy season. Seedling provenance trials (UK) determined photosynthesis, and biomass and δ13C in relation to water table. Environmental data were characterised for all provenances at their sites of origin. Results: Provenances differed in both δ13C and δ15N. Gum yield declined with increasing WUE. Virtually no BNF was detected during the dry season and seedlings and mature trees may have different WUE strategies. Wind speed and soil characteristics at provenance origin were correlated with isotope composition and gum production. Conclusion: Provenance differences suggest that selection for desirable traits, e.g., increased gum production, may be possible. As ecological strategies relate to native locality, the environmental conditions at plantation site and provenance origin are important in assessing selection criteria