Recent preliminary data have suggested that microbe-to-plant signals, and plant internal signals elicited by microbial signals, affect aspects of plant physiology, development and growth. The reported research investigated the responses of plants to signal compounds of microbial and plant origin, such as lipo-chitooligosaccharides (LCOs - signal molecules in rhizobia-legume associations), chitin and chitosan (present in fungal cell walls), and phenolic compounds (salicylic acid, acetylsalicylic acid and gentisic acid - internal signals in plants, often affected by signals from microbes). Phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL) are key enzymes of the phenylpropanoid pathway. Oligomers of chitin and chitosan increased the activities of both PAL and TAL in soybean leaves. The degree of increase was dependent on oligomer chain length and time after treatment. LCO [Nod Bj V (C18:1 , MeFuc)] was isolated from Bradyrhizobium japonicum strain 532C. When Arabidopsis thaliana plants were grown for two weeks on agar containing this LCO (10-8M) or chitin pentamer (10-4 M), they had greater root length, root diameter, root surface area and number of root tips than control plants. Chitosan (tetramer and pentamer) did not have this effect. Chitin and chitosan were also tested for effects on corn and soybean photosynthetic rates and growth. High molecular weight chitosan generally reduced photosynthetic rates, but did not reduce the growth of corn or soybean. However, foliar application of 10-6 M LCO to corn leaves increased photosynthetic rates (up to 36%). Foliar application of lumichrome (10-5 and 10-6 M), a breakdown product of riboflavin produced by some rhizosphere bacteria, to corn (C4 plant) and soybean (C3 plant) increased photosynthetic rates (up to 6%). Foliar application of lumichrome (10-5 M) increased soybean leaf area and shoot dry weight. Foliar application of SA, acetyl salicylic acid (ASA) and gentisic acid (GT

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

The objectives of the investigation were to evaluate no tillage and tillage by plowing with respect to yield of tobacco and corn plants and to compare uptake of P by corn plants from surface and mixed applications of superphosphate. A further aim was to determine the relationship between P uptake by oat plants and inorganic P fractions of three Virginia soils which received varying amounts of superphosphate. During 1963 corn plants were taller on no tillage- and plowed-P fertilized plots than their respective checks, 50 days after planting. Later in the season, 88 to 104 days after planting; height of corn plants on no tillage- and plowed-P fertilized plots were not significantly different than their corresponding checks. From these data it was concluded that P-fertiliser applied to the surface of the no tillage treatment and mixed with soil of the plowed treatment increased growth of corn plants early in the season. Studies with _p32 indicated that surface applied P was more available to corn plants than broadcast-mixed P during the early portion of the 1963 and 1964 growing seasons. Higher yield of corn grain in 1963 from the no tillage treatment was attributed to the higher uptake of surface applied P. During the middle and later portions of the two seasons, surface and mixed applied superphosphate were equally available to corn plants. Because soil temperature and moisture content were not significantly different for the plowed and no tillage treatment it was concluded that these two variables did not influence corn yield. Higher uptake of surface applied P was explained on the basis of less fixation due to less soil-fertilizer contact. This explanation was supported by investigations which showed negligible downward movement of surface applied P and a higher amount of difficulty soluble P compounds in soil of the broadcast-mixed P treatment. It was pointed out that moisture, which does not penetrate deeply into soil, favors plant uptake of surface applied P due to a higher amount of P in solution from surface applied P than broadcast-mixed P. Burley tobacco plants grown on Wellston loam were taller on no tillage than plowed plots early in the growing season. The difference in height was attributed to the higher available water content of the no tillage treatment. Content of N in tobacco leaves at harvest time was lower for plants grown by no tillage. Smaller plants late in the growing season and lower yield for the no tillage treatment were attributed to N deficiency. Presumably, surface applied N (no tillage treatment) supplied less N to plants than mixed N (plowed treatment). The two methods of fertilizer application resulted in equal contents of P and K in tobacco leaves. In a greenhouse investigation, P fertilization increased yield of oat plants on Huntington silt loam and Lloyd clay loam which contained 8 and 26 ppm. of available P (Mehlich test), respectively, but not on Lloyd clay loam which contained 96 ppm. For the soils on which oat plants responded to P fertilizer, uptake of applied P was higher from the Huntington than Lloyd soil whereas the soil test indicated higher amounts of available P for the Lloyd soil. It was concluded that the available P content of the Huntington soil (pH 7.8) was underestimated due to neutralization of the extracting solution. Higher amounts of Al-P and Fe-P than Ca-P were present in the Huntiugton (pH 7.8) than two Lloyd soils (pH 6.9 and 7.0), 28 days after application of S amounts of superphosphate. These data show that considerable amounts of Al-P and Fe-P may form in alkaline and neutral soils. Amounts of Al-P present in the fertilized soils correlated significantly (r = 0.93**) with P uptake by oat plants. From these data it was concluded that Al-P compounds, formed shortly after application of superphosphate, supplied the major portion of P absorbed by oat plants. / Ph. D.

Ph. D.

Thesis (MScAgric (Agronomy))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: See full text for the abstract / AFRIKAANSE OPSOMMING: Sien volteks vir opsomming

Fertilizer P fixation and fertilizer N losses in soils may be reduced through additions of polyphenolic compounds. The influence of ammonium lignosulfonate (NH$ sb4 sp+$-LS) on triple superphosphate (TSP) efficiency was investigated in a soil incubation study using three Quebec soils and in a growth bench study using one soil. For the incubation study, soils were analyzed for pH and P extractability, as a function of NH$ sb4 sp+$-LS rate and time. In the growth bench study, TSP and NH$ sb4 sp+$-LS were applied at varying rates and corn (Zea mays L.) dry matter yields and nutrient compositions analyzed. Similar studies were conducted in subsequent growth bench studies, to evaluate combinations of NH$ sb4 sp+$-LS, diammonium phosphate (DAP), and urea on two soils. / Ammonium LS increased soluble P levels when applied with TSP. The effect was most significant in fine textured soils, and increased with time. This improved P availability to plants, without affecting growth. The optimum NH$ sb4 sp+$-LS:P$ sb2$O$ sb5$ application ratio was approximately 2.8:1. Ammonium LS did not improve availability of DAP-P in either of the subsequent experiments, nor did it improve urea fertilizer efficiency. Some NH$ sb4 sp+$-LS-urea-DAP formulations did, however, improve corn growth beyond that obtained when only urea and DAP were applied in combination. In nutrient amended soils, applying NH$ sb4 sp+$-LS DAP was detrimental to growth and, for some application rates, reduced nutrient uptake.

No description available.

The generalized additive models for location, scale and shape (GAMLSS) developed by Rigby and Stasinopoulos (2005) are a general class of univariate regression models that do not have the response distribution restricted to the exponential family as do the generalized linear and additive models, for example. In addition, they allow all the parameters of the response variable distribution to be modeled explicitly through different sets of explanatory variables. The semiparametric subclass of GAMLSS, in particular, accepts a wide range of parametric and nonparametric terms to be included in the predictors of the parameters. Similar to the generalized linear models, the GAMLSSs link predictors to parameters through monotonic link functions, which can also change for each parameter. This dissertation describes the GAMLSSs methodology and presents two applications to data sets provenient from experiments in agronomy; exploring methods of estimation, diagnosis and comparison of these models. / Os modelos lineares generalizados para locação, escala e forma (GAMLSS) desenvolvidos por Rigby e Stasinopoulos (2005) são uma ampla classe de modelos de regressão univariados que não pressupõem que a distribuição da variável resposta pertença à família exponencial como os modelos lineares generalizados ou aditivos generalizados, por exemplo. Além do mais, eles permitem que todos os parâmetros da distribuição da variável resposta sejam modelados explicitamente por meio de diferentes conjuntos de variáveis explanatórias. A subclasse semiparamétrica dos GAMLSS, em particular, permite que uma grande variedade de termos paramétricos e não paramétricos sejam incluídos nos preditores dos parâmetros da distribuição assumida para a variável resposta. De forma análoga aos modelos lineares generalizados, os GAMLSSs ligam os preditores aos parâmetros por meio de funções de ligação monótonas, que também podem mudar de acordo com o parâmetro a ser estimado. Esta dissertação descreve a metodologia dos modelos lineares generalizados para locação, escala e forma e apresenta duas aplicações a bancos de dados provenientes de experimentos agrícolas; explorando métodos de estimação, diagnóstico e comparação desse tipo de modelos.

The generalized additive models for location, scale and shape (GAMLSS) developed by Rigby and Stasinopoulos (2005) are a general class of univariate regression models that do not have the response distribution restricted to the exponential family as do the generalized linear and additive models, for example. In addition, they allow all the parameters of the response variable distribution to be modeled explicitly through different sets of explanatory variables. The semiparametric subclass of GAMLSS, in particular, accepts a wide range of parametric and nonparametric terms to be included in the predictors of the parameters. Similar to the generalized linear models, the GAMLSSs link predictors to parameters through monotonic link functions, which can also change for each parameter. This dissertation describes the GAMLSSs methodology and presents two applications to data sets provenient from experiments in agronomy; exploring methods of estimation, diagnosis and comparison of these models. / Os modelos lineares generalizados para locação, escala e forma (GAMLSS) desenvolvidos por Rigby e Stasinopoulos (2005) são uma ampla classe de modelos de regressão univariados que não pressupõem que a distribuição da variável resposta pertença à família exponencial como os modelos lineares generalizados ou aditivos generalizados, por exemplo. Além do mais, eles permitem que todos os parâmetros da distribuição da variável resposta sejam modelados explicitamente por meio de diferentes conjuntos de variáveis explanatórias. A subclasse semiparamétrica dos GAMLSS, em particular, permite que uma grande variedade de termos paramétricos e não paramétricos sejam incluídos nos preditores dos parâmetros da distribuição assumida para a variável resposta. De forma análoga aos modelos lineares generalizados, os GAMLSSs ligam os preditores aos parâmetros por meio de funções de ligação monótonas, que também podem mudar de acordo com o parâmetro a ser estimado. Esta dissertação descreve a metodologia dos modelos lineares generalizados para locação, escala e forma e apresenta duas aplicações a bancos de dados provenientes de experimentos agrícolas; explorando métodos de estimação, diagnóstico e comparação desse tipo de modelos.