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Articles by E. Beck
Total Records ( 4 ) for E. Beck
  S. Sikolia , E. Beck , J.I. Kinyamario , J.C. Onyango and G. Ouma
  δ13C values of the Centrospermeae species are presented. 69.5, 28.45, 1.25 and 0.8% of the total species are C3, C4, C3-C4 and CAM photosynthetic species. The δ13C values are species dependent. δ13C values for the C3 range from -21.16 to -30.28‰ while the C4 species vary from -10.60 to -16.55‰. An exceptional δ13C value of -32.28 is reported for Chenopodium capitatum. δ13C value for the CAM species vary from -16.00 to -18.50‰. C3-C4 species includes Mollugo nudicaulis, Portulacaria afra and Portulaca sp. nov. with δ13C values -25.89, -20.93 and -15.66‰, respectively. Temperature and precipitation are the dominant causal climatic factors that influence the distribution of the C3 and C4 species inversely and by extension the δ13C values along the altitude. Other climatic factors act synergistically. A difference in the δ13C values is a biochemical dual function of the Rubisco and suberized lamella anatomical structural organization. The occurrence of some C4 species in the unusual high altitude includes Melandrium nordiflorum and Silene abyssinica and may be due to the Pyruvate Phosphate Dikinase (PPDK) enzyme functional activity. Ecological significances of the δ13C values are discussed.
  S. Sikolia , E. Beck and J. C. Onyango
  The present studies on carbon dioxide compensation point () considered species from tropical semi-arid, snowline and saline ecosystems. The aim of the study was to establish the ecological range of the CO2 compensation point of species in the semi-arid/arid, snowline/or saline conditions. Secondly, to determine the effect of biomass on the rate of carbon dioxide assimilation in relation to the ecological efficiency of the C3 and C4 photosynthetic pathways. Four and six-seven week old plants were used to assimilate carbon dioxide in the gas chamber until a constant reading was attained by Infra Red Gas Analyzer (IRGA). The carbon dioxide uptake concentrations (assimilations) were continuously measured by pumping a stream of the air through a closed gas tight, circuit with IRGA while temperature and light intensity and previous growth conditions were maintained constant. The dry weight of the plant was measured using a digital balance after the experiment. The CO2 compensation points of the C4 plants vary between 8-20 ppm. The CO2 compensation points of the C3 plants vary between 40-60 ppm. The age and biomass of the plant influenced the rate of carbon dioxide assimilation in the C4 species and C3 species. The C4 plant attained the CO2 compensation point faster than C3 plant under the same physiological conditions. The C4 plant photosynthesized below 40 ppm of carbon dioxide concentration. The C3 plant ceased carbon dioxide assimilation below 40 ppm of carbon dioxide concentration. Thus, an ideal ecological canopy set-up should consist of a C4 over storey and a C3 under storey for efficient photosynthetic performance and yield. Potential C4 overstorey species including Amaranthus species and Kochia scoparia, should be intercropped with potential C3 understorey species like Chenopodium album and Phytolaca dioica by farmers and horticulturalists in Agriculture. The intercropping practice is economical, viable and apt in agroforestry systems, especially in the semi-arid and saline conditions socialized by nomadic tribes in Kenya. Perkerra irrigation project can act as satellite agroforestry research station, including Kerio valley and Turkana regions.
  S. Sikolia , J.C. Onyango , E. Beck and J.I. Kinyamario
  Two hundred and seventy eight species of the Centrospermeae were collected at different sites in Western Kenya representing gradients of altitude and aridity. Climate data were obtained from meteorological research stations. Species were examined for C3 or C4 photosynthesis using the anatomical Kranz syndrome, δ13C values and carbon dioxide compensation points. C4 photosynthesis is a feature of modern members of dicotyledoneae is of multiple evolutionary origins. It evolved independently in members of the same family and was found in one to several genera and then often only with two to three species. C4 species are concentrated in lowland habitats subjected to high temperature, low precipitation and high evaporation. High δ13C values is associated with low water availability which is a physiological syndrome and also a feature of saline habitats. The C3 representatives of the Centrospermeae dominate in more moist and colder habitats, especially at higher altitudes. Only a few C4 species occur at high altitudes (3000-4000 m) namely Sagina gallica, Silene abyssinica and Melandrium nordiflorum. The transition zone between C3 and C4-dicot is rather narrow between 1500 to 1700 m and thus much lower than that recorded for the monocots (2000-2200 m). The general pattern of δ13C values distribution along the altitudinal gradient show that the values of -10.60 to -16.55, -17.75 to -18.87 and -18.89 to -32.42‰ that corresponds to altitudinal ranges, 0-1500, 1550-1700 and 1800-4200 m, respectively. The low altitudes are associated with drought and high temperatures. C4 and C3 dicot species can be intercropped to increase bioproductivity for the betterment of the flora and fauna in the semi-arid and arid ecosystem. C4-species are potential candidates for exploitation in the agroforestry systems especially for long-term management programmes. The present study may also be relevant for better understanding of global change with respect to the diversity of photosynthetic pathways, herbivory and vegetation dynamics.
  D.R. Pant , T. Bhattarai , E. Beck and S. Fettig
  Two Nepalese spring wheat cultivars were transformed with an ipt gene from Agrobacterium tumefaciens under the control of the senescence inducible promoter pSEE1 from maize using biolistic method. The resulting transgenic lines, one from Pasang Lahmu and seven from Annapurna-1, were studied for the expression of the transgene and the phenotype characters like chlorophyll content, chlorophylla/b ratio, PS II quantum yield and other parameters of agronomic importance. Analysis of transgene expression by RT-PCR revealed very weak or no signal at all, indicating either partial or complete silencing of the transgene in the lines tested. None of the plants exhibited a phenotype that was significantly different from the respective azygous controls.
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