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Previous work in animal nutrition has focused on single feeds and assumed additivity in ration systems. In the tropics, farmers are likely to feed mixtures of feeds, including tree fodders, which may not be simply additive in nutritional terms. This study has increased our understanding of the mechanisms that determine the associative effects on the in vitro fermentation of mixtures of fodder tree leaves. Associative effects are governed by a synchronisation in the fermentation rates of the components of the mixture. This is in turn dependent on the fermentability of their chemical constituents. Effects were demonstrated by changes in the fermentation kinetics of gas production curves. The chemical components of fodder tree leaves that affect the fermentation, and the time at which the effect occurs, were identified, using two media of different nitrogen contents. The fermentation of mixtures of pure chemical entities in various combinations was then examined. The greatest associative effects were found when the mixture had components of similar fermentability. It is proposed that associative effects are a function of the synchronisation of fermentation of the different components and was shown to occur at the point when the rate was maximal. With two types of protein (casein and bovine serum albumin (BSA)), utilisation of a protein by rumen microbes was shown to be a function of its fermentability and not of its solubility. This is also influenced by the type of associated carbohydrate. Fodder tree leaves were then combined with different pure chemical entities. Associative effects between fodder tree leaves and carbohydrates were shown to occur and the responses were similar to those obtained with mixtures of pure carbohydrates and proteins. The effect of tannins and phenolic compounds was studied using quebracho tannin as a model, and in five of the tree species. They were shown to affect the fermentability of both carbohydrates and proteins. The effect was greater with carbohydrates of medium to low fermentability. They also reacted with both soluble and insoluble protein. Forages with phenolic compounds showed both positive and negative effects. The effects were possible due to a synchrony or asynchrony in the release of protein. In mixtures of leaves from different species, associative effects were related to their fermentability. Again, this appeared to be the result of the synchronisation of the release of nutrients. Associative effects with fodder tree leaves were of a composite nature and can be both positive and negative. The implications of these findings in relation to in vivo digestion and animal production are discussed. Due to the diversity of fodder trees, there is the potential to develop feeding systems based on mixtures which make better use of available resources. This will also contribute to improved efficiency in the management and use of natural resources, and take advantage of natural plant diversity in the tropics.

Heteroblasty defines a dramatic change in leaf form and function along a shoot and is a prominent feature of the genus Acacia (Mimosaceae). Function of different leaf types in Acacia (i.e. compound leaf versus phyllode) is well established yet it is unknown whether heteroblasty is a plastic trait. A fully factorial designed experiment established the light environment, and not nutrients or water, had a significant influence on heteroblastic development. Compound leaves, which have higher specific leaf area (SLA), are retained for longer under low irradiance and, specifically, under a low Red:Far Red light environment. Plants grown in high intraspecific density environments also retained compound leaves for longer. Blue light signals and greater ultraviolet radiation had no effect on heteroblastic development. Heteroblasty is thought to aid in seedling establishment however across all experiments there was no consistent evidence of improved plant performance. Rather, there was an optimal allocation of biomass to organs where resources were most limiting and this was more influential in assisting seedling establishment. Lastly, a meta-analysis of a global dataset of leaf traits found compound leaves to be similar to simple leaves but offset towards the cheap to construct with fast returns region of the leaf economics spectrum.

Heteroblasty defines a dramatic change in leaf form and function along a shoot and is a prominent feature of the genus Acacia (Mimosaceae). Function of different leaf types in Acacia (i.e. compound leaf versus phyllode) is well established yet it is unknown whether heteroblasty is a plastic trait. A fully factorial designed experiment established the light environment, and not nutrients or water, had a significant influence on heteroblastic development. Compound leaves, which have higher specific leaf area (SLA), are retained for longer under low irradiance and, specifically, under a low Red:Far Red light environment. Plants grown in high intraspecific density environments also retained compound leaves for longer. Blue light signals and greater ultraviolet radiation had no effect on heteroblastic development. Heteroblasty is thought to aid in seedling establishment however across all experiments there was no consistent evidence of improved plant performance. Rather, there was an optimal allocation of biomass to organs where resources were most limiting and this was more influential in assisting seedling establishment. Lastly, a meta-analysis of a global dataset of leaf traits found compound leaves to be similar to simple leaves but offset towards the cheap to construct with fast returns region of the leaf economics spectrum.

Leaves play a vital role in the development of a plant, as they are major resource collectors. Adequate models of leaves are therefore required for the modelling of plants. Such models may be used for visualisation purposes only, or they may incorporate leaf function such as photosynthesis. While the modelling of plant architecture has been researched extensively over the last decades, models of leaf surfaces have mostly not been generated with great accuracy or level of detail, and have often been handcrafted. This thesis aims to provide techniques for the creation of detailed, accurate models of leaf surfaces for the plant modelling community; models that may be used as parts of virtual plants for applications in fields as diverse as the arts, agriculture or computer games. These techniques are mathematical methods of surface fitting based on data that has been sampled from real leaves. First, leaf data needs to be collected. The digitising of leaf surfaces is described in detail in this thesis, and issues arising for three data collection techniques are discussed. The laser scanner is selected to sample data from leaf surfaces of four example leaf types. The two surface fitting methods which are applied to the data are finite element interpolation approaches. Since the size of a laser scanned data set can be enormous, an incremental algorithm is used to identify significant points that result in a surface fit that approximates all remaining data points to a specified accuracy. Interpretation of the positions of these points leads to the formulation of guidelines that describe the locations of significant points on a leaf surface. These are the points that should be digitised with a single-point device such as a sonic or magnetic digitiser, possibly the only digitising technique available to a plant scientist. Triangle-based finite element methods lead to surface models with piecewise linear viii boundaries in the triangulation reference plane. This may not be an issue for applications where the boundary of a model is not important. Leaf surfaces, however, possess a specific boundary. To generate a visually realistic model of a leaf surface the boundary needs to be captured; a method is introduced that improves the boundary of a triangle-based interpolant. A new boundary curve is specified that passes through all boundary points, and the surface is extended so that it matches the new curve. Visual criteria are listed for the acceptance or rejection of the boundary, and a preliminary discussion is made of numerical criteria. The research presented in this thesis is the first to model detailed and accurate leaf surfaces based on data points. It delivers a basis for further research both into the application of detailed models as well as into extensions of the presented model.

Thesis (M. Sc.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (leaves 89-94). Also available via the World Wide Web.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references. Also available via the Internet.

Inaug.-diss.--Basel. / Vita. "Separatabdruck von dem "Recueil des travaux botaniques neérlandais", volume XVI, livraison I, 1919." "Literatur-verzeichnia": p. [58]-59.

Thesis (Ph.D.)--Ohio University, November, 2007. / Title from PDF t.p. Includes bibliographical references. Also available online via OhioLINK's ETD Center: http://www.ohiolink.edu/etd/view.cgi?ohiou1188579264

Proefschrift--Utrecht. / "Stellingen": p. [143]-144. "Litteratuuroverzicht": p. [129]-137.