The genetic variability of the yield components in the Kenyan pyrethrum population
SummaryPyrethrum is grown for the insecticidal ‘pyrethrins’, extracted from the dried and ground flowers. It is a cross-fertilizing, self-incompatible perennial plant, which can be propagated vegetatively.The genetic variation of several, commercially important, characteristics was studied. The range of observed variation is very wide for fresh flower yield, flower size, number of flowers per stem, pyrethrins content, lodging resistance and the Pyrethrins I/Pyrethrins II ratio, and quite narrow for the dry matter content of the flowers. Populations to select from are obtained by crossing two (single crosses) or more clones (polycrosses). The genotypic variation of two single and one polycross (42 clones) was studied. The single crosses showed, for the three characteristics measured, pyrethrins content, flower size and Py. I/Py. II ratio, a considerable transgression. The progeny means were very similar to the mid-parent values. This indicates a polygenic inheritance for these traits. The variation of the polycross for these three traits was not greater than those of the two single crosses, suggesting a very high level of heterozygosity in the parental clones. It is in fact possible to reconstitute a large part of the genotypic variation observed in Kenya from only a very few single crosses. In view of the selection relationships between traits were investigated. Flower size appeared negatively related to dry matter content of the flowers and to flower yield. A suspected negative relation between flower yield and pyrethrins content could not be confirmed. The results indicate, that large genetic improvements are possible in a fairly short time.
A Disease of Pyrethrum in Kenya
THE demand for pyrethrum (Chrysanthemum cinerariifolium) resulted in a greatly increased production of this profitable crop in Kenya during the War. It has been cultivated commercially in Kenya since 1928. From 1,864 tons in 1938, the yield rose to 7,409 tons from 52,837 acres in 1945. This acreage is concentrated in a few areas in the Highlands, most of it at an altitude between 6,000 ft. and 9,000 ft. Minor losses, due to root and crown rot, are of common occurrence, but until 1946 the crop had escaped any serious disease in spite of the continuous and intensive cultivation to which it has been subjected.
Fluid to liquid membrane energy exchanger for simultaneous liquid desiccant regeneration and desalination applications–Theoretical and experimental analyses
Abstract In this paper, a thermal model developed for assessing the performance of the fluid to liquid membrane energy exchanger based liquid desiccant regenerator is presented. The model was validated with the experimental data and found accurate. Using the experimental inlet conditions reported in the literature for the structured packing chamber, the performance of the fluid to liquid membrane energy exchanger based liquid desiccant regenerator was theoretically predicted choosing water and air as working fluids and Lithium Chloride as a liquid desiccant. Further, studied the influence of inlet parameters such as working fluid and desiccant inlet temperature’s, hot liquid desiccant to cold working fluid ratio and desiccant concentration on vapour absorption rate. From this analysis, it is observed that membrane based liquid desiccant regenerator using water as a working fluid is best suitable for converting the weak desiccant into strong desiccant and for generating the pure water simultaneously (co-generation process). An experimental investigation was carried out for assessing the energy exchange process across the membrane based liquid desiccant regenerator using water as a working fluid. From the experimental analysis, it was found that desiccant temperature has a significant impact on the energy exchange process. The pressure drop across the membrane based liquid desiccant regenerator was also measured at different desiccant flow rates and concentration.