Theses and Dissertations

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Open Access
Biosystematic Studies of some Species of the Tribe Cichorieae (Asteraceae) in Nigeria.
(Obafemi Awolowo University, 1987) Adegbite, Emman Adegoke; Olorode, O.
Five herbaceous species belonging to four genera of the tribe Cichorieae (Asteraceac) were characterised morphologically and cytologically. The species are Latuca capensis Thunb., Lactuca sativa Linn., Launaea taraxacifolia (Willd) Amin. ex C. Jeffrey, Picris humilis EC and Sonchus oleraceus Linn. The work is aimed at investigating the basis of intra-and inter-specific as well as intra-and inter-generic differences occurring among the species. It is envisaged that both the genetic and environmental components of the morphological differences among the species of the tribe could serve as a clue to the evolutionary relationship of the species. The plants and fruits (achenes) collected from different parts of Nigeria were transplanted or raised from achenes in the screen house to maturity. They were subjected to morphological, cytological (mitotic and meiotic), fertility (using pollen) and leaf anatomical studies. All the species with the exception of L. sativa (cultivated lettuce) are weeds. L. capensis, P. humilis and L. taraxacifolia are perennated by rootstocks and rhizomes, while L. sativa and S. oleraceus are annuals. The intra-specific and inter-specific variability of measured morphological attributes emphasises plastic responses to environmental conditions which characterizes weedy and colonizing species. The close resemblance between P.humilis and L. capensis, their ecological association and the general occurrence of characteristics that are diagnostic of the tribe in all the species suggest some genetic relationship and possibility of inter-generic and inter-specific hybridization among the species of the tribe. The persistence of intra-specific morphological differences in the species collected from different locations when raised under the same conditions implicates the genetic basis of some variations. Mitotic and meiotic chromosime studies corroborate previous observations on chromosome numbers for all the species. L. sativa, P. humilis and L. taraxacifolia have n=9 (2n=18) chromosomes, while L. capensis and S. oleraceus have n=8 (2n=16) and n=16 (2n=32) chromosomes respectively. Meiotic studies reveal normal formation of bivalents, though occasional multivalent associations at diplonema were recorded in L. sativa and L. taraxacifolia. From karyotype studies, the species were assigned karyotypic formulae which indicate numbers, size and centromere position of the chromosomes, L. capensis, 8Cnm; L. sativa, 3A nsm(-) + 3B nsm(-) =3Bnm: L. traxacifolia, 5bnm + 4Cnm; P. humilis, 1Anm + 8Bnm; and S. oleraceus, 2Cm + 14Cnm. The close genetic identity of the species can also be seen in the close pollen size, shape and sculpture. Occurrence of four germ pores on pollens of S. oleraceus underscores the probability that it is a polyloid. Pollen colour corresponds to the colour of the ligule, indicating that the same gene may condition both ligule colour and pollen colour. All the species showed high pollen fertility and anomocytic stomatal tyre.
Open Access
Characterization of the Forest Types of the University of Ife Campus.
(Obafemi Awolowo University, 1986) Chukwuka, Kanayo Stephen; Isichei, A. O.
The rainforest in the University of Ife was characterized by species enumeration and girth measurements, and by attributes derived from these measurements in 17 sample plots. The seventeen plots were located around one of the three hills on the campus, Hill 1, a general uniformity in species composition was observed for all the plots studied with the exception of those on the hill top where Brachystegia eurycoma was found to be dominant and, at times slopes which differed in species composition. The Shannon-Weiner species diversity index for all the plots was in the range 1.88-3.36. Dominance by Manihot glaziovii and Funtumia elastics were, however, observed in two plots. Plots ordination based on species showed plots on the hill top and slopes to be floristically different from those on the flat and gentle surfaces, while the species attributes ordination based on the plots showed that species diversity index, and basal area of species were more important in characterizing the sample plots. The stem girth distribution was generally found in the 11-20cm girth class with the exception of three plots. Two of the plots have high number of big trees in the > 120cm girth class while one has the highest number of stems in the 21-30cm girth class. These observations were discussed in relation to past land use in the area. The nature of succession of these plots was assessed by a modification of Horn's (1975) Markovian change. The application of this model was, however, found not to be satisfactory in assessing the succession of the sampled plots because it showed that regrowth species such as Microdesmis puberula and Napoleons vogelii will form the next generation canopy.
Open Access
Cytological and Morphological Studies on Some Species of Vernonia Schreb (Asteraceae) in Nigeria.
(Obafemi Awolowo University, 1987) Ayodele, Muyiwa Segun; Olorode, O.
Seven species of Vernoxia viz: Yemenis cinerea, V biafrae, V pauciflora , V migeodi, V. temoreama, V. cenferta and V. amygdalina were collected and identified. Two other materials collected could not be identified for lack of appropriate specimens. Studies were carried out on morphological characteristics of some vegetative parts, number of flowers per head, seed characteristics and germinability, and potentials for vegetative reproduction. Studies on somatic chromosomes were carried out with a view to finding out the trend of karyotype evolution and the relationship of the latter to the evolution of growth forms in the genus. The species display a rather complex relationship with respect to their morphological attributes. The sizes of leaves varied among the species in relation to the type of ecological habitat. Three distinct sizes of flower heads (Capitula) were identified. There were variations in Number of florets and seeds per head even among species with about equal sizes of capitulum. The overall number of flowers and seeds per plant was higher in species with smaller flower heads. The small seed sizes were characteristic of species found in open communities. Various adaptive strategies were observed in respect of seed dispersal, germination and seedling establishment in sometimes different habitats from that of adult plants. Chemical or photoperiodic inductive of dormancy is suspected to be responsible for the poor terminability of seeds of some perennial species. The chromosome Numbers of the species fall into two major groups of n = 10 (2a = 20; 2m = 40) and m : 9 (2n = 18). The n = 10 (2n = 20) species include V. migeodi, V. conferta, and V. tenereana. The species with n = 9 (2m = 18) are V. ciuerea, V. biafrae ant V. pauciflora. V. amygdalina was the only polyploid in this study and had 2n = 40. Analysis of karyotype indicates that the n = 10 group seems to be more ancestral and therefore associated with more mature vegetational communities, while the m = 9 croup are more derived and sometimes show weedy tendencies.
Open Access
Ecological Studies of Bryophytes on Unplastered Sandcrete Walls Around Ile-Ife.
(Obafemi Awolowo University, 1986) Akinfenwa, Folasade Olayemi; Odu, E. A.
Some aspects of the ecology of bryophytes on unplastered sandcrete walls around Ile-Ife were investigated over a period of more than 12 months. Two turf-forming bryophytes, Barbula indica and Bryum coronatum, were the commonest mosses encountered on these substrates. No bryophyte was found growing on burnt bricks or mud walls. Whereas Barbula is not a successful species as far as sexual reproduction is concerned, Bryum freely produces sporophytes. Reproduction in Bryum thus includes sexual methods while Barbula reproduces vegetatively by means of gemmae which are produced abundantly on almost every shoot. Gemmae and spores of these mosses, apparently present in the air when washed down by rain, form important sources of new plants on basic substrates. pH is an important factor in controlling the distribution of the mosses. Different stages of development of the moss species, e.g. diaspore germination and protonemal growth are favoured respectively at pH levels 4-12 and 6-10, but maximum shoot growth was observed at pH 10.Under favourable conditions, Bryum shoots establish within 3-4 months but Barbula takes a much longer time to establish.
Open Access
Ecology and Biology of Piliostigma Thonningii (Schum.) Milne-Redhead in the Guinea Savanna Zone of Nigeria.
(Obafemi Awolowo University, 1985) Mbaekwe, Ebenezer Ike; Isichei, A. O.; Sanford, W. W.
Eighteen plots in selected sites from the Mokwa, Kainji and Yelwa areas of the Nigerian Guinea savanna were sampled systematically for vegetation attributes. Four belt transects in each plot were sampled to estimate the density of all woody individuals greater than 1m high, density of Piliostigma thonningii, total basal area of woody species, and woody plant cover. Soil samples were randomly collected from the 0-15cm depth in the plots and analysed for texture organic matter and nitrogen. The vegetation and soil data and attributes derived from them were used for ordinations using principal components analysis. The ordinations show that soil factors namely sand: clay ratio organic matter and nitrogen content were, in association with some vegetation attributes, important in determining the distribution and density of P. thonningii in the areas studied. Some aspects of the biology of the plant were also studied. Best germination results were obtained after acid treatment. The phenology of the plant and its response to perturbations were observed and these observations gave an insight into its mode of propagation. Anatomical studies showed the leaf characters as being semi-xerophytes and the stem as having growth rings. The age of the plant could be estimated from ring counts. Examination of the plant for nodules did not yield positive results but nitrogen levels in the leaves compared favourably with those of other browse plants in the same area. This identifies the plant as an important browse species in the savanna. Overall, the study has highlighted the conditions under which the plant grows and its rich potential as a source of cover and browse in the Guinea savanna.
Open Access
Effect of Soil Texture, Nutrient Stress and Water Stress on Yield of Andropogon Gayanus Kunth and Schizachyrium Sanguineum (Retz.) Alston.
(Obafemi Awolowo University, 1985) Oke, Samson Olajide; Isichei, A. O.
Two grasses, Andropogon gayanus and Schizachyrium sanguineum grown to maturity in fine and coarse sand culture were subjected to nitrogen and water stresses to study how these stresses interact with soil texture in affecting growth and nitrogen accumulation in these grasses. Nutrient-stressing involved administering 200m1 of a nutrient solution containing. 35 parts per million nitrogen once in four days while for water-stressing the same volume of water was fed to the plants at the same frequency. These treatments, if administered once in two days, were considered adequate for the plants. There were two other intermediate treatments. Plants grown in fine sand produced more dry matter the highest yield was adequate nitrogen and water stressing while nutrient and water stressing gave the lowest. The biomass of the two grasses increased with increased nutrient addition to the growth medium. Nutrient stress had a more noticeable effect in reducing yield than water stress. Plants grown in coarse sand had a higher nitrogen concentration than those grown in fine sand. This is attributable to high organic matter content of fine sand the highest yield was adequate nitrogen and water stressing while nutrient and water stressing gave the lowest. The biomass of the two grasses increased with increased nutrient addition to the growth medium. Nutrient stress had a more noticeable effect in reducing yield than water stress. Plants grown in coarse sand had a higher nitrogen concentration than those grown in fine sand. This is attributable to high organic matter content of fine sand grown grasses which led to dilution of nitrogen concentration. In absolute terms, plants grown in fine sand had more nitrogen content. Increasing frequency of nitrogen addition resulted in higher nitrogen content of the grasses. As with yield, giving adequate nitrogen and water-stressing resulted in the highest nitrogen accumulation while water and nutrient stressing gave the lowest. Schizachyrium sanguineum accumulated more nitrogen than Andropogon gayanus because it is more efficient in utilizing nutrients in a low concentration medium. As for plant parts more nitrogen was accumulated in the roots than leaves or stems. The implications of these observations in relation to the natural conditions in which these grasses grow are discussed.
Open Access
Effects of Water Stress on Growth and Aspects of Primary Metabolism of Seedlings of Zea Mays Linn. Variety Farz 27.
(Obafemi Awolowo University, 1985) Ebukanson, Gabriel John; Lawanson, A. O.
Maize seedlings raised for six days were subjected to water stress treatments at 76.6% relative water content (RWC) and 66.5% RWC with appropriate controls. Growth of the maize seedlings, as measured by fresh weights, dry weights, seedling heights, leaf area index, leaf area ratio, leaf weight ratio, net assimilation rate and relative growth rate, was generally retarded by water stress. Water stress, on the other hand, effected enhanced accumulation of chlorophyll a, chlorophyll b, protochlorophyllide, protochlorophyll and phytol in the maize seedlings. The accumulation of carotenes and xanthophylls was enhanced while that of flavonoid was retarded. The levels of mitochondrial quinones, ATPase activities of the chloroplasts and mitochondria' oxidative phosphorylation activity and the activities of succinate, malate and glutamate-dehydrogenases were also generally retarded by water stress. It is suggested that, in water-stressed maize seedlings, the increased accumulation of carotenoids contributed to the increased accumulation of chlorophylls and their precursors. The retarded accumulation of mitochondrial quinones, and the retarded activities of oxidative phosphorylation and those of such enzymes as ATPases, succinate--, malate- and glutamate-dehydrogenases may be responsible for the retarded growth observed in the stressed maize seedlings. Flavonoid accumulation appears to be a better indicator of the effects of water stress on the performance of maize.
Open Access
Genetic and Cytogenetic Studies in some Species of the Genus Crotalaria Linn.
(Obafemi Awolowo University, 1986) Akpabio, Kingsley Essien; Olorode, Omotoye
A collection of the dominant species of Crotalaria was made from different parts of Nigeria. Eight species in all were assembled. These collections were subjected to morphological, cytological and biochemical characterizations. Intra specific and inter specific hybridizations were attempted. Considerable overlap in their vegetative and floral attributes was observed. Statistical analysis of the morphological data has shown that vegetative and frutescence features of Crotalaria plants are important in sub generic and species delimitations. This analysis also shows that qualitative and quantitative characters of flowers, fruits and seeds are important in the identification of Crotalaria species. Observations on the karyotypes and meiotic behaviour of the eight species indicate that six of the species - C. retusa, C. goreensis, C. spectabilis, C. cylindrocarpa C. calycina and C. comosa have somatic complements of sixteen chromosomes (2n=16) each, while two--C.doniana and C.naragutensis--have two accessory chromosomes in addition. The low occurrence of multivalent associations in the diakinesis of each species indicates that the homologues within each genome are considerably distinct structurally. Occurrence of giant cells with large coalesced elements suspected to represent gene amplification is also observed in three species - C. retusa, C. goreensis, and C. cylindrocarpa. Attempt is made to speculate on the evolutionary relationships among the species studied.
Open Access
Genetic Studies on Cassia Occidentalis Linn.
(Obafemi Awolowo University, 1985) Oloruntoba, Oluyemisi Grace; Olorode, O.
Cassia occidentalis is a compound-leaved, mono-capellary, woody shrub of waste places. Its other accession, Cassia sp. is a simple-leaved, multi-capellary, woody shrub also inhabiting waste places but with a more restricted distribution. It is an unusual Cassia plant since multi-capellary condition and the simple leaf form are unusual and apparently unrecorded for the genus. Genetic studies showed both plants to be closely related and to produce a fertile hybrid. The mode of inheritance of leaf form and carpel number was observed to be monogenic, the simple-leaved multi-capellary condition being recessive to the compound-leaved, mono-capellary condition. Anatomical studies on transverse sections through the petiole of the different leaf types encountered in the two accessions, revealed an evolutionary progression which was interpreted as a progression from the simple leaf form to the compound leaf form. The possibility of Cassia sp. originating from C. occidentalis as a result of simple mutational events was suggested. A simple event of hybridization between the two Cassia accessions can create considerable confusion for taxonomic work. For this reason, giving so much weight to the simple-leaf/compound-leaf and one carpe l/ many-carpel dichotomies in suprageneric plant classification deserves considerable caution.
Open Access
Guinea Savanna Structure and Land-use in Northwestern Nigeria.
(Obafemi Awolowo University, 1985) Ero, Isaac Izogie; Sanford, W. W.
The Guinea savanna of northwestern Nigeria was characterised using parameters of climate, soil and vegetation. The scale of variability of the attributes measured in the four localities - Yelwa, Mokwa, Borgu and Jebba - was assessed and found in the case of soil and vegetation to be significant on at least a hectare to hectare scale. Density of all species, the most abundant species, size class distribution, and pattern of woody elements were estimated. Principal component analysis was employed to explore the correlation and variability of soil attributes (sand, silt, clay, organic carbon) and vegetation characteristics between plots and localities. Broad homogeneity in edaphic features was shown, while marked differences existed between plots in each location. The vegetation was heterogeneous in respect of most physiognomic/structural attributes, although considerable homogeneity was observed at Jebba and some at Mokwa. The relative physiognomic/structural heterogeneity was shown to parallel that of soil attributes and in some cases to be directly related to specific soil attributes. The stability and resilience of the sample plots were assessed. The Markovian prediction model gave varying values of weighted relative change showing that successional or maturity class differences are not mainly dependent upon differences in species composition. High diversity indices are related to stability if log-normal species distribution indicated stability, but if geometric species distribution indicates stability then stability is associated with low diversity. It is concluded that land-use and vegetation mapping must done on a local scale permitting the application of management is to delineated land units. The attributes concerning ability (functional/compositional stability) vary in relation to specific land use and should be accordingly assessed. Recommendations are made for such assessment together with listings of parameters most practical for land-use planning in the Guinea savanna.
Open Access
Invasion of Patches of Natural Vegetation by Exotic Woody Species in Obafemi Awolowo University, Ile Ife
(2015-04-10) Akinwande, Ayomiposi Olayinka
The study investigated and determined the extent and pattern of invasion by the exotic woody species, their dispersal mechanism as well as the most successful invaders and why certain areas may be prone to invasion by exotics than others in the University Estate. This was with a view to understanding the patterns and rates of invasion of natural forest by exotic species. The study was carried out in thirteen 25 m x 25 m sample study plots in different parts of the Obafemi Awolowo University Estate, Ile-lfe using forest patches of different successional stages. In each study plot, all the woody plants that were 2 m and above in height were enumerated and identified. A tape was used to measure the girth size of each woody plant at breast height. The height was also measured using a calibrated wooden pole for the short ones and a Haga altimeter for the taller ones. The distance of each of the sample plots from the nearest built-up area and cluster of the exotic plants was recorded. The geographic location of each sample plot was determined using a Garmin global positioning system. The dispersal mechanism of each exotic species was also noted. After the field work, the densities of all enumerated woody plants, both exotic and indigenous in each sample plot were calculated. Histograms of the size class distribution of all enumerated woody plants were prepared and the sample plots compared for rate of invasion/proportion of exotics. Correlation analysis was carried out to determine the significant relationships between plot exotic density and distance from built up areas/cluster of exotics. Ordination of plots and species was also carried out to determine which plots were most prone to invasion, the most successful invaders and the plots with higher species diversity. Results showed that there were 87 woody species consisting of 12 exotic species. Five plots were characterized by young trees mostly in the 0-20 cm size class, four plots were without exotics, two plots had few exotics in the smaller size class, one plot contained only one species of exotic found in the highest size class while one plot had few exotics randomly distributed in the size classes. The six least invaded plots were mostly in their mid successional stages except one that was mature while the five most invaded were mostly early succession plots. Two plots which were in the early/mid successional stages were moderately invaded. The invaded plots were the disturbed ones that were close to the built up areas with a cluster of exotics that were deliberately planted for ornamental purposes. Distance from cluster of exotics was very strongly negatively correlated with exotic density (r = - 0.739, p = 0.01). The same applies to built up, area and exotic density (r = 0.547, p = 0.03). The most successful invaders in this study were Leuceana leucocephala, Delonix regia, Peltophorum pterocarpum, Bauhinia monandra and Azadirachta indica. Seven plots had high species diversity while six plots had low species diversity. The study concluded that most of the plots had been invaded and that disturbance, dispersal mechanism of the exotics, nearness to built up areas and cluster of exotics were major factors in the invasion of forests by exotic species in the Obafemi Awolowo University campus.
Open Access
Metabolic Activities in Seedlings of Maize (Zea Mays Linn. CV. Farz 34) in Relation to Boron Nutritional.
(obafemi Awolowo University, 1985) Besong, Bernard Eshua; Lawanson, A. O.
The responses of maize seedlings to boron nutritional stress were investigated. One group of seedlings was deprived of boron while two other groups were subjected to supraoptimal concentrations of boron conditions by feeding them with five and ten times the optimal concentrations of boron. The effects of supraoptimal concentrations and/or deficiency of boron on the growth rates (as measured by their fresh and dry weights) as well as on the formation of chlorophylls, the specific activity of the ATPases, oxidative phosphorylation, succinate-, malate- and glutamate dehydrogenases, and on the level of mitochondrial quinones were studied. One supraoptimal boron level (X1OB) increased the fresh and dry weights of the seedlings while the other supraoptimal level (X5B) and the deficiency conditions decreased these parameters. Both the supraoptimal boron levels and boron deficiency conditions decreased the amounts of chlorophyll pigments. The specific activity of the respiratory enzymes as well as the level of mitochondria quinones were enhanced under the deficiency and one supraoptimal level (X5B) conditions; the increase being greater in the former group of seedlings. The other supraoptimal level (X10B), however, decreased the activity of the respiratory enzymes.
Open Access
Morphological and Cytological Studies of some Nigerian Species of Tephrosia Pers.
(Obafemi Awolowo University, 1986) Akinwale, Simeon Abiodun; Omotoye, Olorode
The genus Tephrosia Pers. is represented by over 400 species out of which about fifteen are found in Nigeria, out of which seven were considered in this study viz: T. bracteolata Guil'd Perr., T. flexuosa G. Don., T. simplicifolia Frarch, T. barbigeria Welw. ex. Bak., T. linearis (Willd.) Pers., T. elegans Schum. and T .pedicellata Bak. Of these, T. bracteolata is widespread in Nigeria. The genus Tephrosia shows considerable morphological variability. Measurements of the Morphological traits (vegetative and floral) are more or less characteristic for each species, but there is obvious overlap of the measurements in some cases: this underscores the close genetic identity of the species. The close genetic identity can also be seen in the close pollen size and shape. Some aspects of inter-specific and intra-specific variability of the observed attributes can be explained by invoking response of the populations to ecological conditions. From mitotic studies, the most prevalent diploid number of chromosomes of 22 was observed for T. bracteolata, T. flexuosa, T. elegans, T. barbirgera and T. purpurea while the less frequent diploid chromosome numbers of 20 and 16 were found in T. pedicellata and T. simplicifolia respectively. Meiosis is normal in T. bracteolata as seen in the regular bivalent associations and in the normal alignment of the chromosomes on the metaphase plate.
Open Access
Nitrogen and Potassium Leaching Off Inselberg Surface Lichens at the University of Ife.
(Obafemi Awolowo University, 1986) Ekeleme, Friday; Isichei, A. O
The leaching of nitrogen (nitrate-nitrogen and total nitrogen) and potassium off inselberg surface lichens by rainfall on Hill II, University of Ife campus was studied in the period between 11th March and 15th October, 1985. Rain free-fall, surface flow off lichen surfaces on the inselberg and run off from vegetation mats were collected from permanent collecting points after each shower. The nitrate-nitrogen, total-nitrogen and potassium amounts of free-fall were 1.74, 12.33 and 6.18 kgha-1yr-1 respectively. The inputs of these elements were highest in the early part of the rainy season. The concentrations of nitrate-nitrogen, total-nitrogen and potassium leached off the lichens fluctuated widely without any obvious pattern. This is discussed in relation to lichen physiology. Overall, 3.15 kgha-1yr-1 nitrate-nitrogen, 49.73kgha-1yr-1 total-nitrogen and 30.77kgha-1yr-1 potassium was leached off lichen surfaces. The highest concentration of potassium was leached in the first five showers. A comparison of both the concentrations and leaching patterns of total-nitrogen and nitrate-nitrogen off inselberg surface lichens with that leached off the vegetation mats showed that the amounts of these elements leached off the mats fluctuated as much as that leached off the lichens. The amounts of potassium leached off vegetation mats decreased as the season progressed. An estimated 2.3lkgha-1yr-1 nitrate-nitrogen, 32.73kgha-1yr-1 total-nitrogen and 25.l10kgha-1yr-1 potassium was leached off the vegetation mats. The amounts/quantities of these nutrient elements leached off the lichens were on the average higher than that leached off the mats. The estimated quantities (kgha-1yr-1) of nitrate-nitrogen, total-nitrogen and potassium charged to the environment surrounding the inselberg used for the study were 5.46, 82.46 and 55.87 respectively.
Open Access
Some Aspects of the Ecology and Biology of Tephrosia Bracteolata Perr, & Guill (Papiliooideae - Fabaceae).
(Obafemi Awolowo University, 1986) Awodoyin, Rasheed Olufemi; Isichei, A.O.
Some aspects of the ecology and biology of Tepharosia bracteolata, a fodder plant of the Nigerian savanna often growing in association with Andropogoneae grasses, was investigated. The seeds of the plant germinated best after 20 minutes acid treatment. Some good germination was also obtained with heat and boiling water treatment. Growth rates were better in soil enriched with phosphorus than in natural soil. Since one of the aims of the experiment was to examine the feasibility or sowing rangelands with T. bracteolata, field and laboratory studies of competition between it and Andropogon tectorum were carried out. The yields of the plants were higher when grown in mixtures than in monoculutures. Values of relative yield totals for both species were in 11 test densities greater than unity indicating mutual relationship between them. Association analysis showed that the two species were randomly distributed in the field. Soil and vegetation samplings in the field show that T. bractolata does well on acid soils with low organic carbon and nitrogen contents. The crude protein of the loaf samples (12.98%-17.98%) was adequate throughout the growing season to meet the minimal 8% crude protein requirement by animals for milk production. A. tectorum can only supply adequate protein early in the season when its crude protein ranges from 7.04% to 8.21%. Nodulation was observed in T. bracteolata. The presence of leghaemoglobin at the core of the nodules indicates effectiveness in nitrogen fixation. It is suggested that T. bracteolata can be utilized in place of imported pasture species in cropping rangelands. Also, harnessing the nitrogen fixing ability of the plant to improve soil nitrogen content could save the country part of the expenditure on nitrogen fertilizer importation and could reduce environmental pollution resulting from excessive use of the fertilizers.
Open Access
Studies of Abscisic Acid, Cytokinins and Gibberellins in Maturing Fruits of the Oil Palm (Elaeis Guineensis Jaquin)
(Obafemi Awolowo University, 1985) Umoru, Anefi Imhonikhe; Adebona, A.C.
Maturing fruits of the oil palm (Elaeis guineensis JaCquin), were analysed for endogenous abscisic acid, cytokinin and gibberellin activities in relation to the growth rates of such fruits. Soybean callus bioassay was used to determine cytokinin activity both in n-butanol fractions, paper chromatographed and developed in n-butanol: acetic acid water solvent system and in dried, 35% ethanol eluates from LH-20 Sephadex chromatographyl Lettuce hypocotyl and lettuce germination bioassays were used to determine the respective activities of ethyl acetate-and n-butanol- soluble gibberellins and diethyl ether-soluble abscisic acid after subjecting both to thin layer chromatography on silica gel. Developing solvent system for gibberellins was isopropanol: water, while benzene: ethyl acetate: acetic acid was for abscisic acid. The results of the bioassays showed that the hormone activities occurred mainly at Rf values of 0.1-0.2, 0.4.0.5 and 0.7-0,9 for cytokinins; 0.1-0.2; 0.3-0,5 and 0,6-0,8 for gibberellins and 0.4-0.5 for abscisic acid. Co-chromatography with authentic growth substances gave Rf values at 0.7-0.8 and 0.8-0.9 for zeatin and zeatin riboside respectively; 0.7-0.8 for gibberellic acid and 0.4-0.5 for abscisic acid. The drupaceous oil palm fruits increase in growth with time and produced a sequence of gibberellins, abscisic acid and cytokinins, each with four peaks of activity, the fluctuating level of which could be linked to the accelerating, deceleration and asymptotic growth phases. Endogenous gibberellic acid and abscisic acid were tentatively identified in this study. High levels of free gibberellins occurred in the young fruits while the conjugated forms predominated in the mature ones. Four of the six isolated endogenous cytokinins were tentatively identified as zeatin, zeatin riboside, isopentenyladenine and isopentenyladonosine. Although the interconversion between ammonia- and water-soluble cytokinins presented an inconsistent pattern, yet the decrease in the free cytokinins was concomitant with an increase in the conjugated forms in the water-soluble fractions during fruit maturation.
Open Access
Studies on the Productivity of Echinochloa Stagnina (Retz) P. Beauv. in the Kanji Lake Basin of Northern Nigeria.
(Obafemi Awolowo University, 1985) Obot, Emmanuel Asuquo; Sanford., W.W.
Echinochloa stagnina growing in Lake Kainji is identified, described, and separated from Echinochloa pyramidalis and Echinochloa colonaa. The grass has been recognized by cattle farmers as an important source of dry-season fodder for their stock, while the power generation authorities view it as a problem to the Lake's hydrology and optimal power generation due to its contributions to water loss from the lake through evapo-transpiration. Echinochloa stagnina which requires the annual 10 m draw-down of the lake for successful establishment and survival, shows a marked zonation and can potentially cover up to 46% of the lake's surface area. The contribution of the grass to evapotranspirational water loss from the lake accounts for the reduction of the effective lake volume by up to 17%, for example in 1979. A management strategy which demands the harvest and removal, for livestock fodder, of 5% of the total yearly standing crop (up to 120,965.4 tonnes) in order to maintain the grass as a renewable source of dry season fodder without significantly affecting power generation is presented. With such removal an estimated 3 x 106 kg of nitrogen and 4 x 105 kg phosphorus are removable from the lake ecosystem. Sources of nutrients to balance these removals are discussed. Decomposition of Echinochloa stagnina litter in Lake Kainji is rapid and does not fit the general exponential model Wt Woe`-t where Wt is the weight of litter left after time t , W0 is the original weight of litter, k is the decay coefficient and e is the base of the natural logarithm. A mathematical model, the Kainji Lake Echinochloa Model, to calculate the area colonizable by emergent vegetation any given year once the upper and lower water levels of the previous year is known, is presented and tested. A current vegetation map of the Lake is presented; the model has been used to reconstruct the vegetation cover history of the lake.
Open Access
A Study on the Wood Anatomy of some Nigerian Trees with Potential for Pulp and Paper Production.
(Obafemi Awolowo University, 1986) Kpikpi, Walter Mawuli; Olatunji, O. A.
The wood anatomy of sixteen small to medium-sized Nigerian forest trees with potential for pulp and paper production was investigated. Their vegetative morphology was described along with their wood anatomy with a view to finding out their suitability for use as pulpwood. The fibre dimensions and the proportions by volume of various tissues of the wood are reported and the gross wood structure described. The wood ash contents of all 16 species determined were generally low - between 0.98% for Poltophorum pterocarpum and 2.70% for Gliricidia sepium. The woods of only 8 species were extracted with n-hexane, methanol and cold water. The total extractives contents were generally low. The least, 2.50% recorded for Trema guineensis and the highest, 7.35% for Musanga cecropioides.Specific gravity of the woods of all 16 trees was reported while the woods of 8 of the trees with very good anatomical characteristics and vegetative morphology were pulped for paper. The eight species include Musanga cecropioides, Trema guineensis, sepium Ricinodendron heudelotii, Manihot glaziovii, Albizia zygia, Delonix regia and Hildegardia barteri. The physical properties of the laboratory hand paper sheets compared with standard factory-made industrial papers showed that these species are good raw materials for paper-making. Musanga cecropioides was outstanding in the physical strength properties of its paper which showed a high Burst Strength of 4.12 kg/cm2 at pulp freeness of 37 (S.R.) after beating times of 45 minutes.

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