Effects of temperature and light treatment, applied to whole wheat plants, on the growth rates of individual kernels of central spikelets of the intact ear are examined. The treatments applied are the factorial combinations of 10, 15, 20 and 25 °C, and 100, 50 and 25 per cent light over a 2-week period beginning about 2 weeks after anthesis. The growth-rate ratios, which provide information about possible mechanisms responsible for the dry matter partitioning between kernels within a spikelet, are examined in conjunction with a model. An anatomically-based model of the spikelet is constructed and analysed, and the predicted results are compared with the experimental data. It is suggested that the more distal kernels are increasingly handicapped by pathway resistances, but this effect is partly nullified by the fact that the proximal kernels, which are exposed to higher substrate levels, may be operating on the flatter part of a Michaelis-Menten-like response. Further, it is found necessary to assume that the biochemical rate constants (not the Michaelis-Menten constants) of the kernels fall off towards the more distal kernels.
SUMMARY A deterministic model for the spread of an important animal disease, bovine spongiform encephalopathy (BSE), is described. It is a sparse three-pool model, the pools corresponding to susceptible, infected and sick animals. Simulations illustrate the biological meaning of the parameters, and pinpoint how parameters affect epidemic characteristics: infectivity impacts on the leading edge of the epidemic and its intensity. The times when infection is introduced and when control is exercised determine the length and possibly the intensity of the epidemic. Finally, the (single) incubation rate influences the trailing edge of the epidemic. It is applied to data describing the recent UK BSE outbreak, with reasonable success. Apart from a scaling factor, only these four quantities were adjusted to achieve this. The contributions from greater modelling complexity are discussed. It is concluded that the simple model is well suited for grasping the essentials, whereas further detail is needed for a more mechanistic representation, in particular concerning incubation delays in developing infectiousness and clinical sickness.
This article considers the potential of a decolonizing poetics, evident across Tasmanian Aboriginal arts and cultural works, to contribute to a distinctively Aboriginal film-making practice in Tasmania. The potency of this body of work, alongside the Aboriginal community's vigorous political campaigns for cultural rights and land rights, has not translated into a distinctively Tasmanian Aboriginal film culture. Apart from several significant documentary films and photographic works that indicate the emergence of a powerful decolonizing poetics there are no fictional feature films by Tasmanian Aboriginal film-makers. Moreover recent feature films produced by non-Indigenous film-makers about Tasmania invoke the ‘Tasmanian Gothic’ trope, imagining an island without any Aboriginal presence. This article considers processes that contribute to decolonizing through the contemporary work of Tasmanian Aboriginal writers and artists, including Jim Everett, Julie Gough, Greg Lehman and photographer Ricky Maynard. I suggest their poetics are more than textual. They are grounded in country and community—linked. to another realm beyond the ‘shallow’ time of colonization. Their decolonizing poetics are shared with Maori film-maker Barry Barclay's ‘Fourth Cinema’, where the camera is firmly in Indigenous hands, based in community and cultural practices.
Time is discussed first, giving a number of essential but perhaps rather boring relationships between the continuous time variable, day of month, month and Julian day number. Astronomical equations of biological significance are then developed, covering the sun's elevation and azimuth angles, day length, dawn and dusk. The representation of weather in models is discussed, including the need for diurnal data, how this may be generated from daily data, and the generation of daily data from monthly data, either deterministically or stochastically. The relationship between sunshine hours and radiation receipt is addressed, and a version of the Ångström formula is presented. The variable brightness of the sky is examined. Diurnal and seasonal variations of wind speed are considered. The chapter concludes with a short discussion of climate change.
This book comprises six chapters: Introduction (34 pp.), Seasonal response models (60 pp.), Growth response models (91 pp.), Mathematical characteristics of models (97 pp.), Pasture systems (22 pp.) and Nonlinear regression for mathematical models (20 pp.). Each chapter ends with exercises and references. The book has a subject index.
I found the book perplexing for numerous reasons. The preface is signed by the first author alone, with acknow ledgement of the second author. A different chapter order might have been more logical. Parts of the book are almost autobiographical and, perhaps as a consequence of this, appeared repetitive and unfocused. There is much self‐reference, and not enough to others who have contributed to growth functions and growth analysis. The approach is highly empirical, which has its merits, but the authors suggest several times—and wrongly—that they are not just ‘curve fitting’. There is hardly a mention of mechanistic models of crop growth and yield, which is often the method of choice nowadays. Of the 104 figures, 98 present data alongside fitted equations. There is mention of the Schrodinger equation, the harmonic oscillator and hermite polynomials, with reference to some of the iconic names of physics. Much of this seemed of doubtful relevance.
The models applied are mostly the familiar growth equations: polynomial, exponential, hyperbolic, Mitscherlich (or monomolecular) and logistic. The use of the error function as a growth equation was new to me. It worked well as a sigmoidal growth equation; its main drawback is that it defies the type of interpretation available for some of the other growth equations. Here it is presented as a three‐parameter equation. A four‐parameter form can easily be devised in which initial dry mass, final dry mass, and the position and sharpness of the sigmoidal region are all independently specified; this may be of greater utility.
Exercises can be of great value. Chapters 3 and 4 contained 37 and 48 pages of exercises, respectively. These were mostly concerned with fitting growth equations to tabular data, and they rarely illuminated or extended the text.
The first two sentences of the preface state: ‘This book is intended to outline an approach to crop modeling (sic) that I have found to be both mathematically solid and feasible to use in practice. My strategy is to develop the technical details in a way that offers some insight into a logical progression from a simple idea towards more complex details.’ The mathematics is elementary but entirely appropriate and, as far as I worked through it in detail, correct. The method is feasible to use in some practical situations, but is rarely used today because of its limitations—each application is unique and generalization is difficult. I had little sense of ‘a logical progression’.
Who is the intended readership? Students can find review articles or chapters in books which are more accessible, shorter and cheaper. Researchers, who have already read such material, will learn little new here. The book is beautifully produced and printed, with well‐laid‐out equations and carefully annotated figures and tables. Regrettably, I cannot recommend the book to students or researchers, especially given the price.
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A shoot: root partitioning model is presented, which is a development of previous approaches in the area. The model incorporates as a physiologically reasonable apparent 'goal' for the plant, the assumption that the partitioning of growth between the shoot and root maximizes the plant specific growth rate in balanced exponential growth. The analysis is concerned principally with plant growth being a function of carbon and nitrogen only, although it is indicated how other nutrients, or growth factors, may be incorporated. Plant growth is driven by the environmental conditions, and partitioning is defined entirely in terms of the shoot: root ratio and carbon and nitrogen status of the plant. In its basic form the model requires the definition of a single plant growth parameter, along with the shoot and root specific activities and structural composition.
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