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Articles by J.C. Onyango
Total Records ( 4 ) for J.C. Onyango
  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 , 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.
  A.R.O. Nyunja , J.C. Onyango and Beck Erwin
  Kakamega Forest is a rich natural setting endowed with abundant flora and fauna used by the local communities who once lived within the forest and those who now border it. There has been scarcity of information on plants used in basic traditional healthcare by the adjacent communities, Luhya, yet alternative medicine continues to fill in the gap left over by modern medicine. This study sought to survey and document plants used from the forest as medicine or in traditional healthcare and collect, identify and preserve specimens of such plants in the herbarium. Field observation and 240 open-ended interviews conducted during this research have indicated that the people highly value plant medicines for their primary healthcare needs and that the plants are used to cover a wide range of ailments and conditions affecting both man and his domestic animals. The diseases range from topical to internal and psychosomatic ailments, to simple as well as stubborn conditions. Such diseases include whitlow, measles, chickenpox and cancer amongst others. A total of one hundred and twenty herbal practitioners, over 18 years of age, were interviewed between March and September 2002 in this ethno-medicinal study. There have since been bi-annual follow up visits for more information. A total of 168 plant species spanning 74 plant families are reported herein. Moraceae topped the list with 10 species followed by the Euphorbiacea with 9. The most frequently used were Zanthoxylum gillettii, Trichilia emetica, Olea capensis, Entada abyssinica and Croton macrostachyus. The biological diversity, as a phytomedical resource has been indexed thus, contributing to the database of the Kakamega Forest plants. It is hoped that the report will be of use to policy makers. There are several plants with uses hitherto not reported, for instance Craterispermum schweinfurthii an aphrodisiac, Allophylus abyssinica for the hunch back, Ensete edule for measles and Sapium ellipticum for burns. This research has the potential for production and industrialization of the medicinal plants. Medicinal value of plants is hereby fronted as a reason for conserving and preserving biodiversity in Kakamega Forest.
  S. Sikolia and J.C. Onyango
  This study aims to elucidate the ontogeny and organization of the female gametophyte. Further, provide evidences for the strike phenomenon in the Podostemaceae. The female gametophyte ontogeny in Inversodicraea bifurcata Engl. I. keniensis sp. nov. Nagendran et Sikolia conforms to the Apinagia type of the monosporic category. The primary chalazal nucleus degenerates at the two-nucleate stage. The strike phenomenon met in the family is discussed. The organized female gametophyte is four-nucleate, four-celled and consists of two pear shaped synergids, a large central egg cell and a polar cell. Filiform apparatus are present in the synergids. Based on the female gametophyte ontogeny, there are no antipodal cell(s). Earlier reports of double fertilization are not confirmed, but only single fertilization take place in the family. The nucellar plasmodium is rationalized on its organization and ontogeny and is formed before fertilization in Inversodicraea. Effects of tension force and lytic enzymes during nucellar plasmodium organization and its ultimate significance are discussed.
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