Metal accumulation in two contiguous eutrophic peri-urban lakes,Chivero and Manyame,Zimbabwe

Concentrations of aluminium, cadmium, chromium, cobalt, copper, iron, lead, nickel and zinc were determined in surface water, benthic sediments, and the gills, liver and stomach muscle tissues of Oreochromis niloticus and Clarias gariepinus in peri-urban lakes Chivero and Manyame, Zimbabwe. Five sites were sampled in each lake once per month in November 2015, February, May, August and November 2016. Pollution load index detected no metal contamination, whereas the geo-accumulation index reflected heavy to extreme sediment pollution, with Fe, Cd, Zn, Cr, Ni and Cu present in both lakes. Significant spatial temporal variations were detected for Al, Cr, Cu and Pb across sites within and between the two lakes. High Fe, Al and Cr concentrations in water and sediments in lakes Chivero and Manyame derive from geogenic background sources in addition to anthropogenic loads and intensity. Elevated concentrations of Al, Pb, Cu, Cd, Fe and Zn detected in gills, liver and stomach tissue of catfish corroborate concentrations in water and sediments, and pose the highest ecological and health risk for hydrobionts in lakes Chivero and Manyame. Contiguity of peri-urban lakes exposes them to similar threats, necessitating creative water management strategies, which ensure ecological continuity.     

Two Populations of Rh Groups together with Chromosomally Abnormal Cell Lines in the Bone Marrow

At the onset of his disease a man with polycythaemia vera had chromosomally normal cells in the bone marrow and Rh blood group CDe/cDE. Five years later he developed pancytopenia with erythroid hyperplasia of the bone marrow. This was associated with the presence of a major abnormal clone, 45,XY,B-,C-,16+, a minor clone, 45,XY,2+,3-,C-, and a few apparently normal cells. At the same time Rh blood grouping showed two populations of red cells, one CDe/cDE and one giving the reactions of CDe/CDe which can be interpreted as CDe. If monosomic CDe be the correct interpretation the case provides a strong hint that the Rh complex locus is sited either on the long arm of a B-group chromosome or, less probably, on an autosome of the C group.     

An ecophysiological approach to modelling resource fluxes in competing plants

A conceptual model of resource acquisition and allocation within a generalized, individual plant growing vegetatively in competition with others is presented. The model considers C and N acquisition, synthesis of assimilates and their transport and partitioning, growth of new tissues, reserve formation and recycling, and losses due to root exudation and respiration. These processes are regulated by the relative size of the C and N substrate pools in shoot and roots, in relation to meristematic sink strength. Translocation and allocation patterns are represented according to the Minchin phloem transport model. The current model is used to consider the impact of competition on resource acquisition and allocation, first by considering a plant growing in isolation and its response to manipulation of light, CO2 and N supplies. Secondly, competitive plants are introduced and the direct effects on plant responses in terms of resource depletion are considered separately from indirect effects such as potential changes in the quality of resources available (e.g. light quality or soil N sources). In the past, many studies of plant competition have not established the importance of these indirect effects because they have not established all the processes involved in competition. This model can be used to interpret responses of whole plants to their neighbours in terms of the relative importance of both the direct and indirect effects of competition.