Department of Biological Sciences
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Item Studies on the Development and Establishment of Tapinanthus bangwensis1(Oxford University Press, 1971) Onofeghara, F. A.Tapinanthus bangwensis (Engler and K. Krause) Danser is not host-specific in the absolute sense. The pattern of development up to the production of the first two plumular leaves is essentially the same on any host. The parasite, however, shows a preference for some hosts but such preference is independent of any characteristics of the family or order to which the host belongs. Soon after contact with the host surface, the haustorium, the functional root of the parasite begins the penetration process The actual process of invasion is a rapid one and is hidden from view. The effects of crushing, disorganization, and disruption of host tissues that attend invasion point unequivocally to penetration by mechanical action. Considerable though these effects might be cessation of growth of the parasite-bearing host branch is neither early nor common.Item Establishment of in vitro Cultures of Tapinanthus bangwensis (Engler and K. Krause) Danser and the Effects of Sugars on Growth1(Oxford University Press, 1971-11-01) Onofeghara, F. A.Culturing of organs in vitro has been successfully employed in studies on morphogenesis and nutritional requirements of parasitic and semi-paraaitic angiosperms. Tapinanthus bangwensis, a semi-parasite, has been successfully cultured on chemically defined media. By and large the parasite will thrive well in a medium of mineral salts and sucrose at its optimal concentration (4 per cent). However, the parasite is able to metabolize a wide range of sugars most of which show similar concentration optima Although the growth in vivo was simulated in vitro in the early stages, it was found that in the later stages growth in vitro was much slower than growth in vivo. The growth differences observed in the different media may reflect some of the physiological differences that are responsible for the selective nature of the parasite's development and establishment on different hostsItem The Effects of Growth Substances on the Growth of Tapinanthus bangwensis (Loranthaceae) in vitro(Oxford University Press, 1972-06-01) Onofeghara, F. A.The growth response of Tapinanthus bangwensis (Engler and K. Krause) Danser to exogenous growth substances, indole-3yl-acetic acid (IAA), kinetin, and gibberellic acid (GA3), not only varies with the concentrations of each of these substances in the medium but follows a similar trend in each case. Kinetin, IAA, and GA3 were found to enhance growth but not by very appreciable amounts, kinetin being the most effective growth promoter. High concentrations of these substances (5.0 and 10.0 ppm) except GA3 were toxic to the parasite. Gibberellic acid induced the production of accessory leaves at all the concentrations used. Kinetin was also effective in inducing accessory leaves but only at a concentration of 1.0 ppm. Some of the lower concentrations of the growth substances affected significantly some aspects of the parasite's growth and development. Nevertheless, the growth in vitro was still slower than that in vivo.Item The Effects of Photoperiod and Coconut Milk on the Growth of Embryos of Tapinanthus bangwensis in Culture(Oxford University Press, 1973) Onofeghara, F. A.The growth response of Tapinanthus bangwensis (Engler and K. Krause) Danser to photoperiodic treatment varies not only with the photoperiod but also with the composition of the culture medium. By and large, the parasite seems highly tolerant to a wide range of photoperiods. Nevertheless, consistent and significant promotary effects were only observed under a 12-h photoperiod. All other photoperiods (16 h, 8 h, and diffuse daylight) had either promotary or inhibitory effects on different aspects of the parasite's growth. The over-all pattern of growth, however, was the same in all cases. Various concentrations of coconut milk were found to exert different effects on the growth of the parasite, but all the concentrations used supported less growth than the basal medium alone.