Variability in the relationship between tree leaf area (TLA) and selected stem measurements was examined in three Douglas-fir stands (Pseudotsuga menziesii (Mirb.) Franco, var. menziesii) that were less than 50 years-old, spaced to approximately 550 to 650 stems/ha, and differed in soil moisture and nutrients. Attention was given to the effect of mean annual ring width (MARW), cross-sectional area of the live bark (ALB - a surrogate measure of relative nutrient storage in the stem), and cross-sectional area of the most recent annual rings equal in number to the number of whorls in the live crown (ALC), on variability in the relationship between TLA and cross-sectional area of sapwood (ASW). At breast height, basal area, ASW, and cross-sectional area of sapwood plus live bark (ASWLB) were not linearly related to TLA, and linear regression equations using log transformed variables varied significantly between sites. Nonlinear regression equation for ASW at breast height was: TLA = 0.064ASẆ¹•³³ (I² = 0.856). Including D (the distance between breast height and the center of the live crown) in the nonlinear equation, did not significantly improve the regression. Tree leaf area prediction models using stem measures from the base of live crown (blc) had higher adjusted R² values than models using stem measures from breast height. At the blc, basal area, ASW, and ASWLB were linearly related to TLA (adjusted R² = 0.926, 0.908, and 0.934, respectively). Multiplying ASW by MARW did not improve the fit of the regression models. Multiplying ASW by ALB improved the linearity of the relationship of ASW at breast height to TLA. The best fitting TLA model overall used the product of ASW at blc and ALB at blc as the independent variable (adjusted R² = 0.967). The results indicate that research into the allometric relationship of TLA to stem measures should give consideration to more than hydraulic measures and include measures of bark function. At breast height and the blc, the independent variable ALC was linearly related to tree leaf area and had higher adjusted R² values than did ASW. In most trees the ALC stem measure was found to include a portion of heartwood area. The strong relationship between TLA and ALC suggests that a given transpiring leaf mass or area is related to a proportional amount of conducting stemwood and physical support stemwood. A quick alternative approach for estimating individual tree leaf area using photographs taken at fixed distance and angle from the target tree did not result in a reliable tree leaf area prediction technique. The difficulty of obtaining views of the tree crown which were not obstructed by adjacent tree crowns was the major obstacle. Using a fixed distance and camera angle was a problem because of variable tree heights. However, altering these fixed positions introduced additional variation into the tree leaf area estimation. Mean specific leaf area (SLA) varied significantly by site, needle age class, and crown position. Mean SLA per needle age class per branch can be predicted with 95% confidence and a 10% allowable error using six 10-needle samples. / Forestry, Faculty of / Graduate

Although leaf movements have been documented for over a century, there are few studies focused on the adaptive significance of leaf movements, especially with experiments under controlled conditions. The major objective in this study is to determine the ecological significance of leaf movements in Rhododendron maximum, which is a subcanopy, evergreen species distributed in seasonally cold environments. Leaf movements could be necessary for maintaining a favorable energy balance and/or avoiding photoinhibition and photooxidation. A series of leaf manipulation treatments were established to verify these potential explanations. These leaf treatments were designed to separate the influence of leaf curling and leaf angle on leaf energy budget, gas-exchange characteristics, chlorophyll contents and leaf longevity. Leaf movements were found to have a significant influence on leaf physiology and longevity of R. maximum. Without changes in leaf angle, chlorophyll contents decreased, and permanent photoinhibition occurred due to excess irradiance absorption in the winter. Leaf angle also influenced leaf temperature although the changes in leaf temperature were within the physiological tolerances of R. maximum leaves. Leaf curing had little or no effect on the parameters measured in the study. / M.S.

No description available.

Compositional nutrient diagnosis was used to evaluate the nutritional status of trees located in the Abitibi region of Quebec in order to determine the effects of species (white birch, conifer (balsam fir and white spruce), stand are (31, 51, 72, and 125 years) and parent material (lacustrine clay and glacial till) on foliar nutrient concentrations. Significant differences were found in foliar nutrient concentrations between the three species growing on similarly classified sites. The age of the stand significantly influenced the foliar nutrients of trees, illustrated by the significant decrease in foliar nitrogen concentration on clay and till and phosphorus concentrations on clay with stand age irrespective of species. Foliar nutrient concentrations varied significantly between parent materials. Trees of all species growing on clay stands exhibited deficiencies in nitrogen and conifers also exhibited severe deficiencies in magnesium. On till, deficiencies of potassium for birch, magnesium for conifer, and phosphorus for poplar were observed.

Ph.D. / Please refer to full text to view abstract

Please read the abstract in the section 00front of this document / Thesis (PhD (Soil Science))--University of Pretoria, 2007. / Plant Production and Soil Science / unrestricted

No description available.

A determinação de macro- (N, P, K, Ca, Mg e S) e micronutrientes (Fe, Cu, Mn, Zn, B, Mo, Cl e Ni) em folhas de plantas é recomendada para avaliar o estado nutricional das culturas de interesse econômico. A análise convencional envolve a decomposição ácida do material vegetal, geralmente assistida por radiação micro-ondas, seguida da determinação dos elementos por ICP OES. Nesta tese, duas técnicas multielementares foram avaliadas para acessar o status nutricional da cultura da soja rapidamente: a espectrometria de emissão óptica com plasma induzido por laser (LIBS) e a espectrometria de fluorescência de raios X dispersiva em energia (EXDRF). Mapas microquímicos foram construídos empregando-se um sistema LIBS constituído por um laser de Nd:YAG (1064 nm, 5 ns, 360 mJ, 10 Hz) e um espectrômetro com óptica Echelle e detector ICCD, e um equipamento de bancada de micro-fluorescência de raios X dispersiva em energia (µ-EDXRF Orbis PC, EDAX) com tubo de Rh (50 kV, 50 W) e SDD. As distribuições elementares de Mg, Ca, P, S e K foram avaliadas, a fim de orientar e definir uma estratégia de amostragem para análise foliar direta da soja. Os mapas indicaram que a micro-heterogeneidade intrínseca dos elementos avaliados na amostra é significativa e há variações da composição foliar, tanto entre plantas de um mesmo tratamento, quanto entre folíolos de uma mesma planta. Esses fatores foram considerados críticos na definição de uma estratégia de amostragem única que pudesse abarcar e contornar os possíveis efeitos causados por esses fatores. Assim, definiu-se amostrar a maior área possível, sem privilegiar qualquer região específica da folha. Uma prova de conceito foi realizada, empregando-se LIBS para diagnose foliar de soja. Como as folhas secas de soja apresentaram baixa resistência mecânica, 30 folhas frescas de soja foram analisadas por LIBS, sendo acumulados 25 pulsos de laser por linha no modo de varredura, 12 linhas por folíolo e 3 folíolos por planta. Os resultados obtidos foram promissores em termos de comprovar a viabilidade técnica e prática do emprego de LIBS para análise direta de folhas frescas de soja. Análises de folhas frescas de soja também foram realizadas empregando-se um espectrômetro portátil de fluorescência de raios X dispersiva em energia (Tracer III-SD, Bruker) equipado com tubo de Rh (4W, 50 kV, 4,5 mm de diâmetro de feixe de raios X) e SDD. O status nutricional de plantas cultivadas sob condições controladas, com fornecimento adequado de nutrientes (tratamento controle) e com deficiência induzida de fósforo foi avaliado. Boas correlações foram obtidas para P (r = 0,838) e Zn (r = 0,888), que permitem inferir que a EDXRF pode ser recomendada para a quantificação desses nutrientes no campo. Os sinais detectados de Ca, Cu, Fe, K, Mn, P, S, Si, Zn e Rh (espalhamento Compton) permitiram a classificação das amostras em grupos utilizando análise de componentes principais (PCA). Os gráficos de scores e loadings da PCA mostraram: i) a separação entre os dois grupos de amostras (controle e deficientes em P), e ii) quais elementos foram responsáveis por esta separação. Dessa forma, a PCA constitui uma alternativa à análise quantitativa e pode ser utilizada em conjunto com EDXRF para identificar e classificar as amostras de soja como saudáveis ou deficientes em P. Assim, a partir dos resultados obtidos nesta tese, pode-se concluir que ambas as técnicas, LIBS e EDXRF, têm potencial para avaliar o estado nutricional da soja em tempo real, in situ e com mínimo tratamento de amostras. No entanto, para alcançar resultados quantitativos, diferentes estratégias de amostragem e calibração devem ser avaliadas criteriosamente a fim de superar os desafios aqui apresentados e criar condições de contorno para os inconvenientes que as folhas de soja apresentam como, por exemplo, a distribuição não-homogênea dos elementos e a baixa resistência mecânica quando secas / The determination of macro- (N, P, K, Ca, Mg and S) and micronutrients (Fe, Cu, Mn, Zn, B, Mo, Cl and Ni) in plant leaves is recommended to evaluate the nutritional status of crops of economic interest. Traditional analysis involves microwave-assisted acidic digestion the plant material, followed by determination of the elements by ICP OES. In this thesis, two multielemental techniques were evaluated to access the nutritional status of the soybean crop quickly: laser-induced breakdown spectroscopy (LIBS) and energy dispersive X-ray fluorescence spectrometry (EXDRF). Microchemical maps were built using a LIBS system constituted by a Q-switched Nd:YAG laser (1064 nm, 5 ns, 360 mJ, 10 Hz) and a spectrometer with Echelle optics and ICCD detector, and a benchtop micro-energy dispersive X-ray fluorescence spectrometer (?-EDXRF Orbis PC, EDAX) with Rh X-ray tube (50 kV, 50 W) and SDD. The elemental distributions of Mg, Ca, P, S and K were evaluated in order to guide and define a sampling strategy for direct analysis of soybean leaves. Maps indicated that intrinsic micro-heterogeneity of the elements evaluated in the sample is significant and there are variations in the leaf composition, between plants of the same treatment and between leaflets of the same plant. These factors were considered critical in defining a single sampling strategy that could encompass and circumvent the possible effects caused by them. Thus, it was decided to sample the largest possible area, without privileging any specific region of the leaf. A proof of concept was carried out using LIBS for foliar diagnosis of soybean. As the dry leaves of soybean presented low mechanical resistance, 30 fresh leaves of soybean were analyzed by LIBS, employing 25 laser pulses per line in the rastering mode, 12 lines per leaflet and 3 leaflets per plant. The obtained results were promising in order to prove technical and practical feasibility in using LIBS for direct analysis of fresh leaves of soybean. Analyzes of fresh leaves were also performed using a portable energy dispersive X-ray fluorescence spectrometer (Tracer III-SD, Bruker) equipped with Rh X-ray tube (4W, 50 kV, 4.5 mm diameter of X-ray beam) and SDD. The nutritional status of plants grown under controlled conditions, with good supply of nutrients (control treatment) and with phosphorus-induced deficiency were evaluated. Good correlations were obtained for P (r = 0.838) and Zn (r = 0.888), which allow to infer that EDXRF can be recommended for the quantification of these nutrients in the field. The detected signals of Ca, Cu, Fe, K, Mn, P, S, Si, Zn and Rh (Compton scattering) allowed the classification of samples into groups using Principal Component Analysis (PCA). The PCA scores and loadings graphs showed: i) the separation into two sample groups (control and P deficient), and ii) which elements were responsible for this separation. So, PCA constitutes an alternative method to quantitative analysis and it can be used with EDXRF in order to identify and classify soybean samples as healthy or P deficient. Thus, from the results obtained in this thesis, it can be concluded that both techniques, LIBS and EDXRF, have the potential to evaluate the nutritional status of soybean in real time, in situ and with minimal sample treatment. However, in order to achieve quantitative results, different sampling and calibration strategies should be carefully evaluated aiming to overcome the challenges presented here and circumvent the drawbacks of soybean leaves, such as the nonhomogeneous distribution of the elements and the low mechanical resistance when leaves are dried

A determinação de macro- (N, P, K, Ca, Mg e S) e micronutrientes (Fe, Cu, Mn, Zn, B, Mo, Cl e Ni) em folhas de plantas é recomendada para avaliar o estado nutricional das culturas de interesse econômico. A análise convencional envolve a decomposição ácida do material vegetal, geralmente assistida por radiação micro-ondas, seguida da determinação dos elementos por ICP OES. Nesta tese, duas técnicas multielementares foram avaliadas para acessar o status nutricional da cultura da soja rapidamente: a espectrometria de emissão óptica com plasma induzido por laser (LIBS) e a espectrometria de fluorescência de raios X dispersiva em energia (EXDRF). Mapas microquímicos foram construídos empregando-se um sistema LIBS constituído por um laser de Nd:YAG (1064 nm, 5 ns, 360 mJ, 10 Hz) e um espectrômetro com óptica Echelle e detector ICCD, e um equipamento de bancada de micro-fluorescência de raios X dispersiva em energia (µ-EDXRF Orbis PC, EDAX) com tubo de Rh (50 kV, 50 W) e SDD. As distribuições elementares de Mg, Ca, P, S e K foram avaliadas, a fim de orientar e definir uma estratégia de amostragem para análise foliar direta da soja. Os mapas indicaram que a micro-heterogeneidade intrínseca dos elementos avaliados na amostra é significativa e há variações da composição foliar, tanto entre plantas de um mesmo tratamento, quanto entre folíolos de uma mesma planta. Esses fatores foram considerados críticos na definição de uma estratégia de amostragem única que pudesse abarcar e contornar os possíveis efeitos causados por esses fatores. Assim, definiu-se amostrar a maior área possível, sem privilegiar qualquer região específica da folha. Uma prova de conceito foi realizada, empregando-se LIBS para diagnose foliar de soja. Como as folhas secas de soja apresentaram baixa resistência mecânica, 30 folhas frescas de soja foram analisadas por LIBS, sendo acumulados 25 pulsos de laser por linha no modo de varredura, 12 linhas por folíolo e 3 folíolos por planta. Os resultados obtidos foram promissores em termos de comprovar a viabilidade técnica e prática do emprego de LIBS para análise direta de folhas frescas de soja. Análises de folhas frescas de soja também foram realizadas empregando-se um espectrômetro portátil de fluorescência de raios X dispersiva em energia (Tracer III-SD, Bruker) equipado com tubo de Rh (4W, 50 kV, 4,5 mm de diâmetro de feixe de raios X) e SDD. O status nutricional de plantas cultivadas sob condições controladas, com fornecimento adequado de nutrientes (tratamento controle) e com deficiência induzida de fósforo foi avaliado. Boas correlações foram obtidas para P (r = 0,838) e Zn (r = 0,888), que permitem inferir que a EDXRF pode ser recomendada para a quantificação desses nutrientes no campo. Os sinais detectados de Ca, Cu, Fe, K, Mn, P, S, Si, Zn e Rh (espalhamento Compton) permitiram a classificação das amostras em grupos utilizando análise de componentes principais (PCA). Os gráficos de scores e loadings da PCA mostraram: i) a separação entre os dois grupos de amostras (controle e deficientes em P), e ii) quais elementos foram responsáveis por esta separação. Dessa forma, a PCA constitui uma alternativa à análise quantitativa e pode ser utilizada em conjunto com EDXRF para identificar e classificar as amostras de soja como saudáveis ou deficientes em P. Assim, a partir dos resultados obtidos nesta tese, pode-se concluir que ambas as técnicas, LIBS e EDXRF, têm potencial para avaliar o estado nutricional da soja em tempo real, in situ e com mínimo tratamento de amostras. No entanto, para alcançar resultados quantitativos, diferentes estratégias de amostragem e calibração devem ser avaliadas criteriosamente a fim de superar os desafios aqui apresentados e criar condições de contorno para os inconvenientes que as folhas de soja apresentam como, por exemplo, a distribuição não-homogênea dos elementos e a baixa resistência mecânica quando secas / The determination of macro- (N, P, K, Ca, Mg and S) and micronutrients (Fe, Cu, Mn, Zn, B, Mo, Cl and Ni) in plant leaves is recommended to evaluate the nutritional status of crops of economic interest. Traditional analysis involves microwave-assisted acidic digestion the plant material, followed by determination of the elements by ICP OES. In this thesis, two multielemental techniques were evaluated to access the nutritional status of the soybean crop quickly: laser-induced breakdown spectroscopy (LIBS) and energy dispersive X-ray fluorescence spectrometry (EXDRF). Microchemical maps were built using a LIBS system constituted by a Q-switched Nd:YAG laser (1064 nm, 5 ns, 360 mJ, 10 Hz) and a spectrometer with Echelle optics and ICCD detector, and a benchtop micro-energy dispersive X-ray fluorescence spectrometer (?-EDXRF Orbis PC, EDAX) with Rh X-ray tube (50 kV, 50 W) and SDD. The elemental distributions of Mg, Ca, P, S and K were evaluated in order to guide and define a sampling strategy for direct analysis of soybean leaves. Maps indicated that intrinsic micro-heterogeneity of the elements evaluated in the sample is significant and there are variations in the leaf composition, between plants of the same treatment and between leaflets of the same plant. These factors were considered critical in defining a single sampling strategy that could encompass and circumvent the possible effects caused by them. Thus, it was decided to sample the largest possible area, without privileging any specific region of the leaf. A proof of concept was carried out using LIBS for foliar diagnosis of soybean. As the dry leaves of soybean presented low mechanical resistance, 30 fresh leaves of soybean were analyzed by LIBS, employing 25 laser pulses per line in the rastering mode, 12 lines per leaflet and 3 leaflets per plant. The obtained results were promising in order to prove technical and practical feasibility in using LIBS for direct analysis of fresh leaves of soybean. Analyzes of fresh leaves were also performed using a portable energy dispersive X-ray fluorescence spectrometer (Tracer III-SD, Bruker) equipped with Rh X-ray tube (4W, 50 kV, 4.5 mm diameter of X-ray beam) and SDD. The nutritional status of plants grown under controlled conditions, with good supply of nutrients (control treatment) and with phosphorus-induced deficiency were evaluated. Good correlations were obtained for P (r = 0.838) and Zn (r = 0.888), which allow to infer that EDXRF can be recommended for the quantification of these nutrients in the field. The detected signals of Ca, Cu, Fe, K, Mn, P, S, Si, Zn and Rh (Compton scattering) allowed the classification of samples into groups using Principal Component Analysis (PCA). The PCA scores and loadings graphs showed: i) the separation into two sample groups (control and P deficient), and ii) which elements were responsible for this separation. So, PCA constitutes an alternative method to quantitative analysis and it can be used with EDXRF in order to identify and classify soybean samples as healthy or P deficient. Thus, from the results obtained in this thesis, it can be concluded that both techniques, LIBS and EDXRF, have the potential to evaluate the nutritional status of soybean in real time, in situ and with minimal sample treatment. However, in order to achieve quantitative results, different sampling and calibration strategies should be carefully evaluated aiming to overcome the challenges presented here and circumvent the drawbacks of soybean leaves, such as the nonhomogeneous distribution of the elements and the low mechanical resistance when leaves are dried

No description available.