Histochemical Localization of Enzymes in the Cucurbitaceae Acid Phosphatases: Acid Phosphatases

Histochemical localization of acid phosphatases was successfullycarried out on the steins of Cucumis, Cucwbita and Colocynthis—threeof the most important genera of the Cucurbitaceae whose speciesare cultivated for their fruits in the tropics. The localizationsshowed generally widespread activity and similarity in distributionfor this enzyme in the tissues of these plants. For each plantacid phosphatase activity decreased with age. The possible significanceof these localizations has been discussed in the light of thedistributional evidence and the roles usually ascribed to thisenzyme. Conventional histochemical techniques for the localizationof acid phosphatase have also been evaluated.     

Distribution and morphology of extrafloral nectaries in some Cucurbitaceae

A study of extrafloral nectaries has been made in the Cucurbitaceae to ascertain their structure and assess their taxonomic potential. Nineteen species representing nine Old World genera and one New World genus were examined. These included Telfairia occidentalis, Telfairia pedata, Momordica charantia, Lagenaria siceraria, Citrullus lanatus, Luffa aegyptiaca, Cucurbita moschata and Trichosanthes cucumerina , which are of economic importance and cultivated in Nigeria for their leaves and/or fruits.
Observation of the regularity of ant and insect-visitors, along with tests for glucose and β-glucosidase enzymes, revealed the presence of extrafloral nectaries in nine species. Considerable variation exists in the distribution and morphology of nectaries between genera, especially in the tribe Benincaseae. The nutritional and ecological significance of the occurrence of extrafloral nectaries in Telfairia occidentalis is discussed.     

The Effects of Growth Substances on the Growth of Tapinanthus bangwensis (Loranthaceae) in vitro

The growth response of Tapinanthus bangwensis (Engler and K.Krause) Danser to exogenous growth substances, indole-3yl-aceticacid (IAA), kinetin, and gibberellic acid (GA₃), not only varieswith the concentrations of each of these substances in the mediumbut follows a similar trend in each case. Kinetin, IAA, andGA₃ were found to enhance growth but not by very appreciableamounts, kinetin being the most effective growth promoter. Highconcentrations of these substances (5.0 and 10.0 ppm) exceptGA₃ were toxic to the parasite. Gibberellic acid induced theproduction of accessory leaves at all the concentrations used.Kinetin was also effective in inducing accessory leaves butonly at a concentration of 1.0 ppm. Some of the lower concentrationsof the growth substances affected significantly some aspectsof the parasite's growth and development. Nevertheless, thegrowth in vitro was still slower than that in vivo.     

Histochemical Localization of Alkaline Phosphatases and {beta}-Glucosidases in Cucurbitaceae

The distribution of alkaline phosphatases and ß-glucosidasesin the tissues of the stems of Colocynthls citrullus, Cucumissativus and Cucurbita pepo was studied. There was similarityin the pattern of distribution for these two groups of enzymesand that of acid phosphatases. The activities of these enzymesvaried not only from plant to plant but also from tissue totissue. However both enzymes showed increasing activity withplant age and localization was correspondingly more restricted.The significance of these localizations is discussed.     

The Effects of Photoperiod and Coconut Milk on the Growth of Embryos of Tapinanthus bangwensis in Culture

The growth response of Tapinanthus bangwensis (Engler and K.Krause) Danser to photoperiodic treatment varies not only withthe photoperiod but also with the composition of the culturemedium. By and large, the parasite seems highly tolerant toa wide range of photoperiods. Nevertheless, consistent and significantpromotary effects were only observed under a 12-h photoperiod.All other photoperiods (16 h, 8 h, and diffuse daylight) hadeither promotary or inhibitory effects on different aspectsof the parasite's growth. The over-all pattern of growth, however,was the same in all cases. Various concentrations of coconutmilk were found to exert different effects on the growth ofthe parasite, but all the concentrations used supported lessgrowth than the basal medium alone.     

Studies on Pyricularia oryzae Cav. in Sierra Leone: Morphological and Physiological Variability of Some Isolates

The morphological and physiological variability of six isolatesof Pyricularia oryzae, the causal organism of rice blast disease,were investigated. The rate of growth, colony characters, andtime of sporulation were found to vary with the different isolatesthough not by appreciable amounts. Each of the isolates showedconsistently better growth on Takahashi's B medium than on Czapek-Dox'smedium although the growth trend was the same in both media.The colony characters developed by each isolate are not dependenton the medium on which it is growing—a pointer to thefact that such characters may be genetically controlled. Germinationwas faster in distilled water than in 2 per cent agar. All theisolates produced appresoria in vivo and in vitro; those producedin vivo were, however, considerably larger than those producedin vitro. On the basis of appresorial types, the isolates werefound to fall into two physiological races—smooth-walledand rough-walled. Each isolate produced consistently only oneappresorial type in vitro from the apical or basal cell of theconidium. The utilization of carbon and nitrogen compounds variedfrom one isolate to the other, carbon compounds being generallybetter utilized than nitrogen compounds. Pyricularia oryzaecan metabolize a wide range of carbon compounds. However, mannose,sucrose, glucose, fructose, and maltose proved to be most suitablecarbon sources. The variations in the utilization of the variouscarbon and nitrogen compounds seem to reflect inherent biochemicaland physiological differences among the isolates.     

Establishment of in vitro Cultures of Tapinanthus bangwensis (Engler and K. Krause) Danser and the Effects of Sugars on Growth

Culturing of organs in vitro has been successfully employedin studies on morphogenesis and nutritional requirements ofparasitic and semi-paraaitic angiosperms. Tapinanthus bangwensis,a semi-parasite, has been successfully cultured on chemicallydefined media. By and large the parasite will thrive well ina medium of mineral salts and sucrose at its optimal concentration(4 per cent). However, the parasite is able to metabolize awide range of sugars most of which show similar concentrationoptima Although the growth in vivo was simulated in vitro inthe early stages, it was found that in the later stages growthin vitro was much slower than growth in vivo. The growth differencesobserved in the different media may reflect some of the physiologicaldifferences that are responsible for the selective nature ofthe parasite's development and establishment on different hosts     

Studies on the Development and Establishment of Tapinanthus bangwensis

Tapinanthus bangwensis (Engler and K. Krause) Danser is nothost-specific in the absolute sense. The pattern of developmentup to the production of the first two plumular leaves is essentiallythe same on any host. The parasite, however, shows a preferencefor some hosts but such preference is independent of any characteristicsof the family or order to which the host belongs. Soon aftercontact with the host surface, the haustorium, the functionalroot of the parasite begins the penetration process The actualprocess of invasion is a rapid one and is hidden from view.The effects of crushing, disorganization, and disruption ofhost tissues that attend invasion point unequivocally to penetrationby mechanical action. Considerable though these effects mightbe cessation of growth of the parasite-bearing host branch isneither early nor common.