Beck E

Publications (3)0 Total impact

• Article: The Distribution of C₃ and C₄ Photosynthetic Species of the Centrospermeae Along an Altitudinal Gradient in Western Kenya

  Sikolia S, Onyango J.C, Beck E, Kinyamario J.I
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  ABSTRACT: 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 C₃representatives 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.
  International Journal of Botany. 01/2009;
• Article: Carbon Dioxide Compensation Points of Some Dicots of the Centrospermeae Species and Their Ecological Implications for Agroforestry

  Sikolia S, Beck E, J. C. Onyango
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  ABSTRACT: 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 C₃and 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 CO₂compensation point faster than C₃plant 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.
  International Journal of Botany. 01/2009;
• Article: δ<SUP>13</SUP> Values of the Centrospermeae Species and Their Ecological Implications in the Semi Arid Conditions

  Sikolia S, Beck E, Kinyamario J.I, Onyango J.C, Ouma G
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  ABSTRACT: δ<SUP>13</SUP>C values of the Centrospermeae species are presented. 69.5, 28.45, 1.25 and 0.8% of the total species are C<SUB>3</SUB>, C<SUB>4</SUB>, C<SUB>3</SUB>-C<SUB>4</SUB> and CAM photosynthetic species. The δ<SUP>13</SUP>C values are species dependent. δ<SUP>13</SUP>C values for the C<SUB>3</SUB> range from -21.16 to -30.28 while the C<SUB>4</SUB> species vary from -10.60 to -16.55 . An exceptional δ<SUP>13</SUP>C value of -32.28 is reported for Chenopodium capitatum . δ<SUP>13</SUP>C value for the CAM species vary from -16.00 to -18.50 . C<SUB>3</SUB>-C<SUB>4</SUB> species includes Mollugo nudicaulis , Portulacaria afra and Portulaca sp. nov. with δ<SUP>13</SUP>C values -25.89, -20.93 and -15.66 , respectively. Temperature and precipitation are the dominant causal climatic factors that influence the distribution of the C<SUB>3</SUB> and C<SUB>4</SUB> species inversely and by extension the δ<SUP>13</SUP>C values along the altitude. Other climatic factors act synergistically. A difference in the δ<SUP>13</SUP>C values is a biochemical dual function of the Rubisco and suberized lamella anatomical structural organization. The occurrence of some C<SUB>4</SUB> 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 δ<SUP>13</SUP>C values are discussed.
  International Journal of Botany. 01/2008;