Search

Low bioavailability of phosphate (P) due to low concentration and high immobility in soils is a key limiting factor in crop production. Application of excess amounts of P fertilizer is costly and by no means sustainable, as world-wide P resources are finite and running out. To facilitate the breeding of crops adapted to low-input soils, it is essential to understand the consequences of P deficiency. The second messenger calcium (Ca2+) is known to signal in plant development and stress perception, and most recently its direct role in signalling nutrient availability and deficiency has been partially elucidated. The use of Ca2+ as a signal has to be tightly controlled, as Ca2+ easily complexes with P groups and therefore is highly toxic to cellular P metabolism. It is unknown whether Ca2+ signals P availability or whether signalling is altered under P starvation conditions. The aim of this PhD project was to characterise the use of Ca2+ ions, particularly cytosolic free Ca2+ ([Ca2+]cyt), in stress signalling by P-starved roots of the model plant Arabidopsis thaliana. The hypothesis was that under P starvation and a resulting decreased cellular P pool, the use of [Ca2+]cyt may have to be restricted to avoid cytotoxic complexation of Ca2+ with limited P groups. Employing a range of genetically encoded Ca2+ reporters in Arabidopsis, P starvation but not nitrogen starvation was found to strongly dampen the root [Ca2+]cyt increases evoked by mechanical, salt, osmotic, and oxidative stress as well as by extracellular nucleotides. The strongly altered root [Ca2+]cyt response to extracellular nucleotides was shown to manifest itself during seedling development under chronic P deprivation, but could be reversed by P resupply. Fluorescent imaging elucidated that P-starved roots showed a normal [Ca2+]cyt response to extracellular nucleotides at the apex, but a strongly dampened [Ca2+]cyt response in distal parts of the root tip, correlating with high reactive oxygen species (ROS) levels induced by P starvation. Excluding iron, as well as P, rescued the altered [Ca2+]cyt response, and restored ROS levels to those seen under nutrient-replete conditions. P availability was not signalled through [Ca2+]cyt. In another part of this PhD project, a library of 77 putative Ca2+ channel mutants was compiled and screened for aberrant root hair growth under P starvation conditions. No mutant line showed aberrant root hair growth. These results indicate that P starvation strongly affects stress-induced [Ca2+]cyt modulations. The data generated in this thesis further understanding of how plants can integrate nutritional and environmental cues, adding another layer of complexity to the use of Ca2+ as a signal transducer.

Following Russell Re Manning, I acknowledge the diversity and persistence of natural theology. Going further than Re Manning, however, I propose a 5-type taxonomy stretching from natural theology as natural religion to natural theology as theology of nature. Having met this descriptive responsibility, I then turn in a second chapter to prescriptive possibility in dialogue with the Anglican theologian Howard E. Root (1926–2007). An early advocate of natural theology and the arts, Root called in his 1962 essay, “Beginning All Over Again,” for awareness (i.e., of the arts) rather than formal argument. Critiqued by E.L. Mascall and others, Root responded in his 1972 Bampton Lectures, “The Limits of Radicalism.” Never published, I discovered these lectures in an uncatalogued box at Lambeth Palace Library, London. Drawing upon these lectures, as well as other archival materials, I consider Root's contribution to a natural theology of the arts. That said, Root's work requires further development, and so in an effort to recover Root I have supplemented his contribution with the more recent work of David Brown, his unacknowledged theological heir. In an effort to recover Root more fully I turn in a third chapter to consider the philosopher William Desmond, the result of which is a metaxologically reformulated Root-Brown hybrid. In a fourth and final chapter, I consider the American contemporary artist Jonathan Borofsky and several others in order to see how this theoretical frame might be applied in practice as a metaxological natural theology of the arts.

Globally, soils contain more carbon (C) than vegetation and the atmosphere combined. Despite clear importance to the global C budget, estimates of C fluxes into and out of soils remain highly uncertain. Decomposition is the dominant process by which C is lost from soil, but most of what is known about the controls of this process comes from studies of leaf litter at the soil surface. My first two chapters explore factors affecting the decomposition of two common belowground litter types. Chapter one is a global meta-analysis of the drivers of fine root decomposition, and is the first to explore the effects of species-level traits in addition to climate and substrate chemistry. My second chapter describes an experiment characterizing the dynamics and chemical drivers of fungal necromass decomposition, an important and understudied flux of soil C. My final chapter focuses on the role of soil fungi in the formation of “stabilized” soil C in the form of mineral associated organic matter (MAOM). Here, I call into question the current assumption that new MAOM formation in soil occurs in close proximity to root surfaces. Using quantitative estimates of fungal exploration, I put forth the hypothesis that fungal hyphae play an underappreciated role in distributing C through soil, and that hyphal contact with minerals encourages the formation of MAOM. This work suggests that current potential for MAOM formation in soils is significantly underestimated by not accounting for the impact of fungi.

Polarized cells are frequently partitioned into subdomains with unique features or functions. As plant cells are surrounded by rigid walls, polarized cell shape and protein polarity in the plasma membrane are particularly important for normal physiology and development. Here we identify and characterize WALLFLOWER (WFL), a transmembrane receptor kinase that is asymmetrically distributed to the inner face of epidermal cells. In epidermal hair (H) cells in the elongation and differentiation zones, WFL exhibits a dual polar localization, accumulating at the inner domain as well as at the root hair initiation domain (RHID). While WFL localization to the inner polar domain remains constant regardless of cell identity, its localization is affected by deletion of the intracellular domains. Polar localization of truncated WFL varies depending on cell identity indicating the WFL intracellular domains are important for informing cell type-specific positional information. Additionally, we observe that polar accumulation of WFL at specific plasma membrane domains is achieved and maintained by constant de novo protein secretion via a Brefeldin A sensitive endomembrane trafficking pathway. While wfl mutants don’t have a detectable abnormal phenotype, overexpression of WFL leads to a downward shift in root hair (RH) position. However, RH position is unaffected upon deletion of WFL intracellular domains, indicating that the kinase domain is required to inform RH position. Additionally, we find that roots overexpressing WFL-GFP are also sensitive to mechanical stress and prone to cell damage. However, this phenotype can be alleviated by cell wall rigidification or maintaining stable osmotic conditions. These observations, together with the shifted RH phenotype, suggest that WFL may have a role in coordinating cell wall modification with cellular expansion during RH development. We propose WFL participates in a signaling pathway that links cues from the inner cell layers of the root with polar growth at the epidermal surface, informing RH position.

Abstract: OBJECTIVE: To analyze the relationship between the impacted maxillary canine and the root inclination of the adjacent maxillary incisors. While earlier literature relied on 2-dimensional radiographs, which display an overlapped representation of the maxillary incisors, this project had the advantage of using 3-dimensional imaging to measure each maxillary incisor root inclination independently. METHODS: CBCTs of 27 patients with palatally impacted maxillary canines (group P), 15 patients with buccally impacted canines (group B), and 30 patients with normally erupting maxillary canines (group C) were used in our analysis. Incisor root inclination with respect to the palatal plane was measured for each individual maxillary incisor, and an ANOVA was used to assess significant differences for each incisor between the 3 groups. Paired T-tests were conducted in groups P and B to evaluate whether or not lateral or central incisors on the side of the impacted canine showed significant differences in inclination from their contralateral counterparts. Factors such as distance away from the adjacent lateral incisor, vertical position of the canine crown, and impaction sector were recorded for each patient in groups P and B. These factors were included in Pearson correlation analyses also considering the adjacent lateral incisor’s root inclination. All three statistical analyses were repeated after patients with peg-shaped/small maxillary lateral incisors were removed from the groups (3 in group P, 2 in group B, 1 in group C). RESULTS: Compared to group C, lateral incisors on the side of the palatally impacted canine showed an average of approximately 10 degrees more buccal root inclination, and central incisors on the affected side averaged about 5 degrees more buccal root inclination. Group B showed significant differences in the ipsilateral lateral incisor alone, which averaged 12 more degrees of palatal root inclination when compared to group C. Within group P, the ipsilateral lateral incisor averaged 7.5 more degrees of buccal root inclination than its contralateral counterpart. In comparison, the central incisor on the affected side averaged 3 degrees more buccal root inclination than that of the contralateral side. In group B, the lateral incisor immediately adjacent to the buccally impacted canine displayed an average of approximately 10.5 degrees more palatal root inclination than the contralateral side. In group P, moderate correlations revealed that the closer and more coronally positioned the impacted canine is with respect to the lateral incisor, the more buccally inclined the lateral incisor’s root will be. A moderate correlation also showed that the more medially displaced the palatally impacted canine is situated (i.e., the higher the impaction sector), the more buccally inclined the adjacent lateral incisor’s root would be. In group B, a considerable correlation showed that the more medial the impacted canine was, the more palatally inclined the root of the lateral incisor would be, however this finding should be interpreted with caution since only two cases in group B had their canines situated in impaction sector 4-5. After peg-shaped/small laterals were removed, group P no longer showed significant differences in ipsilateral central incisor inclination compared to group C. Furthermore, the variable of impaction sector no longer shared a significant correlation with incisor root inclination in group P. Additionally, average root inclinations of all maxillary incisors demonstrated less buccal root inclination in group P and less palatal root inclination in group B. CONCLUSION: Patients with impacted maxillary canines do not show significant differences in the root position of all four maxillary incisors, but only in the incisors on the side of the impacted canine. While palatal impactions are associated with buccally positioned roots of both the ipsilateral lateral and central incisors (with different degrees of inclination), buccal impactions are only associated with palatally placed roots of the ipsilateral lateral incisors.

CASEIN KINASE 1 (CK1) is an ancient protein kinase conserved across all eukaryotes that is well known for regulating cytoskeletal components, cell proliferation, and circadian rhythms. Evidence of CK1’s functional importance in other eukaryotes suggests the Casein Kinase 1-like (CKL) family in Arabidopsis might also be regulators of important biological pathways in plants. CASEIN KINASE 1-LIKE 12 (CKL12) is one of thirteen serine/threonine protein kinases within the CKL family. This study of CKL12 presents ckl12 mutants with mild growth defects under various conditions that implicate CKL12 as a positive regulator of primary root growth and shade avoidance response. Evidence here shows that brassinosteroid (BR)-related transcription factors (TF) positively regulate CKL12 transcription. Western blotting and confocal imaging of transgenic lines overexpressing CKL12 suggest that this protein is post-translationally regulated. Confocal imaging also shows overexpressing CKL12 tagged with green fluorescent protein localizes in a pattern that is reminiscent of other CKLs suggesting possible similar functions within the family. This early research indicates that CKL12 is probably being temporally restricted in the developing Arabidopsis seedling which should streamline future investigations of this protein.

Nitrogen is an essential element for plant nutrition. Nitrate and ammonium are the two major inorganic nitrogen forms available for plant growth. Plant preference for one or the other form depends on the interplay between plant genetic background and environmental variables. Ammonium-based fertilization has been shown less environmentally harmful compared to nitrate fertilization, because of reducing, among others, nitrate leaching and nitrous oxide emissions. However, ammonium nutrition may become a stressful situation for a wide range of plant species when the ion is present at high concentrations. Although studied for long time, there is still an important lack of knowledge to explain plant tolerance or sensitivity towards ammonium nutrition. In this context, we performed a comparative proteomic study in roots of Arabidopsis thaliana plants grown under exclusive ammonium or nitrate supply. We identified and quantified 68 proteins with differential abundance between both conditions. These proteins revealed new potential important players on root response to ammonium nutrition, such as H+ -consuming metabolic pathways to regulate pH homeostasis and specific secondary metabolic pathways like brassinosteroid and glucosinolate biosynthetic pathways.

While microbes inhabit a wide array of environments, their ability to live within host tissue and become tolerated as part of a select microbial community is perhaps one of the most impressive feats of microbial resilience and survival. Host microbiome establishment and maintenance requires both host-microbe and microbe-microbe interactions. Among plant hosts, benefits from associated microbiomes are known to include improved growth, development and resistance to abiotic and biotic stresses. Mammalian microbiomes are known to improve host digestion, influence inflammation and even improve immune response to pathogens. While host-associated microbial communities across all domains of life are incredibly diverse, a growing number of studies are finding host-specific taxonomic trends, suggesting microbiome conservation and evolutionary selection. However, we have come to recognize that there is often functional redundancy between taxa. Therefore, investigative focus on microbiome composition potentially neglects pivotal and influential microbial players. Shifting focus to function over form creates the opportunity to tease apart the driving forces of unique microbiome constituents. This allows for identification of strains and genes of interest as well as microbial selections. To that end, here we describe the relationships between hosts and microbiomes as well as between microbes in two vastly different host systems (Figure 1.1). First, we suggest that plant root-associated Streptomyces isolates harboring genes encoding an enzyme and its co-factor are more tolerant of phenolic compounds generated by roots. Next, we address the capability of these Streptomyces isolates to employ their metabolic repertoires to influence the composition of the root microbiome. Finally, we define a previously under-described role for the gut microbiome in malaria immunology and suggest that gut microbial composition can modulate the severity of malarial disease. Together, these findings demonstrate the broad implications of microbiome composition across diverse hosts and environments, revealing unexplored opportunities for therapeutic interventions aimed at improving plant and human health.

The most expensive maneuver for an interplanetary spacecraft is the orbital injection. One approach to find minimum fuel-cost trajectories is to preform a search over a number of design parameters such as radius of periapse, apoapse of the insertion orbit, and angle of approach. The so-called V-infinity leveraging maneuver has been shown to reduce the design space by implementing a small burn at apoapse to modify the velocity vector at a flyby body. The focus of the present work is orbital insertion of a science mission at Jupiter or Saturn, with the end goal of rendezvousing with a high-science priority moon such at Titan or Europa. The orbital insertion phase is framed as a boundary-value problem with a 1-D minimization over Time-Of-Flight (TOF) and assumes two body dynamics which enables both rapid and broad trajectory searches. Specifically, a search over Body-Plane (B-Plane) Angle and TOF is presented and then, upon finding a minimum-[Delta] V B-Plane Angle, searches over radius of periapse. Additionally, analytic solutions for B-Plane Angle are derived for the special cases of minimum inclination, node/apse alignment, and moon/apse alignment.

Ecosystem processes are fundamentally limited by nutrient availability, but the effects of nutrient limitation or co-limitation on key processes like root nutrient uptake and carbon (C) exudation into soils is relatively unknown. New paradigms of nutrient limitation suggest that colimitation by multiple nutrients is more common than single nutrient limitation, therefore the established view that ecosystem processes are limited by phosphosus (P) in lowland tropical forests on highly weathered soils ecosystems should be revisited. Rates of nutrient uptake are of particular importance because these govern downstream plant physiological processes like photosynthesis and basic metabolism. Also, nutrient uptake is directly linked to root C exudates, which are increasingly recognized as an important plant contribution to soil C pools. Here, we explored the effect of changes in nutrient availability on root nutrient uptake in a well-studied Panamanian forest, and linked nutrient uptake to C exudates. We used a long-term factorial nutrient fertilization experiment, and focused our study on a relatively abundant canopy tree species (Tegtragastris panamensis). We found a significant interacting effect of nitrogen (N) and potassium (K) on root uptake rates for ammonium, nitrate, and phosphate. Nitrogen and K added in combination produced uptake rates indistinguishable from control plots, however, N or K added individually increased the uptake rates of all nutrients compared to control and NK plots. No significant effects of N or P addition were observed on root C exudation rates. These results suggest that increased N or K availability may accelerate N and P uptake rates by roots. These results support the growing literature indicating that most ecosystem processes in tropical forests are governed by the availability of multiple nutrients, with implications for understanding plant productivity in this biome.

Double-cropping with forages can increase yields and N-use efficiency over sole-crop systems, but reductions in primary crop yield can limit economic returns. This study assessed whether the combination of high value, forage, early maturing corn varieties, and reduced N inputs constitutes an economically viable, low N-input double crop system for Minnesota. Biomass yield, N uptake, and residual soil N were measured in two double-crop (DC) and one sole-crop (SC) systems at site-years in MN, from 2014 to 2016. In DC treatments, a pea- (Pisum sativum L.) barley (Hordeum vulgare L.) forage bi-culture was double-cropped with early-maturing hybrid (DC-HC) or semidwarf (DC-SD) corn (Zea mays, L.) varieties. In SC treatments, full-season hybrid corn (SC-HC) was planted with no preceding forage. Corn was supplied with 6 N rates (0 to 224 kg N ha-1 for each yield component. Corn yielded less biomass in DC-HC (8.2 Mg ha-1) and DC-SD (1.8 Mg ha-1) treatments yielded compared to SC-HC (16.3 Mg ha-1). Biomass yield deficits lowered corn N demand in DC-HC treatments so that N rates >166 kg N ha-1 did not limit biomass yield in DC-HC treatments, where SC-HC corn was limited by N rate in three of four site-years. Total biomass accumulation was similar between DC-HC and SC-HC treatments when forage bi-culture yielded >7 Mg ha-1. This suggests that double-cropping with high-quality forages may constitute an economically viable low N-input alternative to sole-crop corn production in Minnesota.

Introduction: Technological advances in three-dimensional imaging of the dentition have provided orthodontists with more diagnostic information than ever. This study evaluated the effect of root and bone visibility on perceptions of the quality of treatment simulations to assess how the use of advanced imaging such as cone-beam computed tomography (CBCT) may influence treatment planning decisions. Methods: An online survey was used to present 141 orthodontists with setups (digital models of teeth) generated for 10 patients in 2 different types of view: with and without bone and roots as modeled from a cone-beam computed tomography scan. Using a 100-point visual analog scale, the orthodontists were asked to rate the quality of the setups from poor to ideal, and, if applicable, to identify features of concern that led them to giving a setup a less than ideal rating. Results: The quality ratings were significantly lower when roots and bone were visible in the setups (P

Plants are crucial to our lives; they provide us with building materials, oxygen, and food. A season’s crop yield can be significantly affected by local environmental factors. Farming practices currently focus on using fertilizer, pesticides, monitoring water availability, and genetic modification of the plant to increase crop yield. Improving fundamental understanding of plant root interactions with their local soil environment, or rhizosphere, will help improve crop yield. Studying such interactions is challenging because roots are underground, making it difficult to observe interactions and to manipulate the local soil environment. The goal of this thesis is to develop an automated mini-channel platform to investigate how plant roots respond to changes in their environment. Corn seedlings were grown inside the transparent mini-channel device. The automated system maintains the level of growth medium in the device to ensure the plant stays hydrated. A digital camera regularly images the root growing in the device. The images are processed to characterize the root’s growth. The device accommodates electrochemical sensors to measure changes in nitrate concentration. The automated platform was developed to simplify researching plant root-environment interactions, with the goal of improving crop yields. It measured corn’s growth rate over time, and determined that the con consumed nitrate over time. The platform’s adaptable design, simple fabrication, and low cost make it simple to replicate and use to study different plants and environmental stimuli. Improving our understanding of different plant root-environment interactions will be crucial in improving crop yields to match expected population growth. Advisor: Sangjin Ryu

Recent years have shown an increased interest in biochar, a high carbon compound made from pyrolyzed biomass. Biochar is a carbon negative product that has been suggested as a soil amendment. Studies have shown disagreement on the effect of biochar on plant growth and on anion leaching from biochar amended soils. Three experiments were conducted to investigate biochar’s effect on plant growth and on nitrogen and phosphorus leaching. Chapter one focuses on biochar’s effect on root growth. Bread wheat (Triticum aestivum L.) cv. Pavon 76 and Pavon 1RS.1AL were grown in a sandy loam soil amended with sand (50% by weight) and/or biochar (~1.5% by weight). Results indicated that the 1RS.1AL plants had more roots and deeper roots and biochar addition resulted in more root growth, likely due to changes in soil texture. A second study was conducted to investigate nitrogen and phosphorus leaching from Begonias (Begonia semperflorens ‘Viva’) grown in nursery conditions. Different amounts of biochar, ranging from 0% to 30% by weight, were incorporated into potting mix and the amount of nitrate, ammonium and phosphate leached from each pot was measured. No difference in plant growth was detected, but high rates of biochar did reduce the amount of nitrate, ammonium and phosphate leached. The last chapter investigated the biochar’s ability to adsorb nitrate, ammonium and phosphate when added to tall fescue (Festuca arundinacea) turf. Plots were either direct seeded or transplanted as sod with high, low or no biochar applied to the plots. Although plots with transplanted plants clearly leached more nitrate, ammonium and phosphate, the effect of biochar on leaching was less substantial. However, the results do seem to indicate that the biochar does reduce some leaching. Overall, the affect biochar had minimal effect plant growth in these experiments. The begonias showed no change in shoot growth. However, wheat plants tended to have more roots when grown with biochar. Additionally, when the results of the leaching studies for both the begonia experiment and the turf experiment are taken in aggregate, it’s clear that biochar can reduce the amount of nitrate, ammonium and phosphate leached.

Objectives: To determine if distinct patterns of aortopathy exist in patients with bicuspid aortic valves (BAV) and to characterize the association of aortopathy with valve morphology and dysfunction.Methods: We analyzed preoperative 3-dimensional computed tomography reconstructions for 656 patients with BAV undergoing ascending aorta surgery from 1/2001 to 1/2014. Partitioning around medoids was used to cluster patients based on data-driven similarities. Differences between groups were compared with a polytomous random forest model.Results: Three distinct morphologic aneurysm patterns were identified: root (n=83, 13%), ascending (n=364, 55%), and arch phenotype (n=209, 32%). Severe valve regurgitation was most prevalent in root phenotype (57%), followed by ascending (34%) and arch (26%; p < 0.0001). Aortic stenosis was most prevalent in arch phenotype (62%), followed by ascending (50%) and root (28%; p < 0.0001), and this relationship persisted when stenosis became severe (36%, 21%, and 11%, respectively; p < 0.0001). Patient age increased as extent of aneurysm became more distal (root; 49 years, ascending; 53 years, arch; 57 years; p < 0.0001) and root phenotype was associated with male predominance compared to ascending and arch (94%, 76%, and 70%, respectively; p < 0.0001).Conclusions: Patterns of aortopathy in BAV patients have different underlying pathophysiology. Root phenotype patient characteristics suggest a genetic etiology while ascending and arch aneurysms may have more hemodynamic underpinnings.

Introduction: Persistent pain following root canal treatment (RCT), a common dental procedure, can be either of odontogenic or nonodontogenic origin. The prognosis for patients experiencing such pain is dependent on differentiating patients into these 2 categories and deriving specific diagnoses, since appropriate treatment various dramatically. This study aims to present the proportions of specific diagnoses these patients have and provide information about their signs and symptoms, including radiographic findings. Methods: This study was nested within a parent prospective observational study that followed up patients for 6 months following RCT. Patients meeting criteria for persistent pain at 6 months and living in Minnesota were considered eligible cases. Cone-beam Computed Tomography (CBCT) and dental radiographs were obtained and patients were individually evaluated by an endodontist and an orofacial pain practitioner to derive consensus diagnoses. Results: A total of 38 patients met the criteria, of which 19 were evaluated. Odontogenic reasons for persistent pain occurred less frequently than nonodontogenic reasons (42% vs. 53% respectively). There was an overlap of odontogenic and nonodontigenic reasons in 10% of the patients. About 16% reported some level of pain that seemed to be related to normal "healing". Of patients with odontogenic reasons, about one third was related to the previously treated tooth and the other two thirds were related to adjacent teeth. Temporomandibular pain disorder (TMD) was the most common nondontogenic reason for pain, comprising 42% of all patients and 80% of those with nonodontogenic pain. Persistent dento-alveolar pain disorder (PDAP) was less common, comprising 10% of all patients and 20% of those with nonodontogenic pain.Conclusion: Data from this study help in quantifying the frequency of odontogenic versus nonodontogenic reasons for persistent pain following RCT.

Streambank erosion is a growing concern in Minnesota as hydrologic conditions continue to change throughout the state. Plant root anchoring and surface protection from vegetation play a role in reducing erosion. The Rosgen Bank Assessment for Non-point source Consequences of Sediment (BANCS) method of erosion prediction uses both root density and surface protection to estimate the resistance of a streambank to erosion. In order to understand how different types of vegetation can influence parameters within the BANCS system thirty sites were selected in the Glacial Lake Plain, Glacial Till, and Loess regions. Root sampling and vegetation surveys revealed no correlation between root density and erodibility factors from the BANCS system. Data from this study can assist restoration efforts in these regions in order to improve or refine current practices, reduce erosion and improve water quality.

Drought is the most important abiotic stress adversely affecting soybean (Glycine max (L.) Merr.) yield. Leaflet orientation has been shown to reduce leaflet temperatures and transpiration while root morphology has been related to slower wilting phenotypes. The objective of this study was to investigate effects of leaflet orientation and rooting morphology on whole plant transpiration, yield, water use efficiency, and other physiological traits in soybeans using grafting techniques, population lines, near-isogenic lines, and restrained leaf canopy experiments. Experiments were conducted in Knoxville, TN with additional yield trial plots at Springfield, Spring Hill, and Milan, TN. Data were collected on whole plant transpiration, seed yield, leaflet orientation phenotype, root morphology, PAR, SAR, maturity, height, lodging, biomass accumulation, leaf area, photosynthesis, canopy light penetration, seed size, seed protein and oil. Grafting experiments revealed that plant shoots affected many of the measured traits but did not condition root phenotype. Root effects on measured traits were not significant. Effects of scion and root morphologies on measured traits could not be separated from genetic differences of the lines grafted. Population line analysis found no clear association between leaflet orientation and transpiration or yield. Leaflet orientation associated with some traits but those associations reflected the phenotype of parental lines, suggesting genetic linkage. Orienting leaves had cooler temperatures relative to leaves receiving direct sunlight. High orienting lines allowed more sunlight penetration into lower canopy which had a positive effect on mid-canopy photosynthesis. Leaflet orientation correlated with root morphology. Overall, root morphology had little effect on measured traits. Leaflet orientation and root morphology frequency distributions approximated normal distributions suggesting traits are polygenic. Experiments with near-isogenic lines detected no consistent patterns or significant effects due to differing leaflet orientation and root morphology on measured traits. This may have been due to lack of prominent differences in leaflet and root phenotypes between isogenic line pairs. Restrained canopy evaluations revealed no statistical differences in whole plant transpiration rates between plants allowed to orient leaves versus those with leaflets restrained. Further research is needed to investigate the effects of leaflet orientation and root morphology on yield and other physiological characteristics in soybean.

This report discusses two methods of visualizing complex solutions of polynomials: modulus surfaces and vector fields. Both provide valuable information about the location of complex solutions and their multiplicity. A sketch of a proof of The Fundamental Theorem of Algebra utilizing modulus surfaces and complex analysis is also included.

As global temperatures rise, understanding the effects of increased temperature on daily carbon dioxide fluxes is necessary to predict changes to the global carbon cycle. Using tunable diode laser spectroscopy, I measured CO2 fluxes and changes in isotopic composition of root respiration, leaf respiration and photosynthesis over a 12-hour night to day transition. I found that after a 10°C increase in growth temperature for four weeks, root CO2 fluxes acclimated to the higher temperature (i.e. they were not significantly different from controls). In contrast, both photosynthesis and respiration of leaves were higher at the elevated growth temperature. Though the root fluxes were not significantly different between growth temperatures, two patterns may become significant with greater replication: (1) the difference in rates of mid-day/mid-night root respiration in plants grown at 22°C may be greater than those grown at 32°C and (2) variability in the isotopic composition of root respired CO2 is greater during the mid-night period compared to mid-day period. These data show that leaves and roots respond differently to grow temperature and suggest that root respiration during the day may respond to temperature differently from root respiration at night.

Lucerne (Medicago sativa L.) is an important legume for New Zealand dryland farms. To ensure the productivity and persistence of lucerne stands rotational grazing is recommended. However, over spring ewes and lambs are typically set-stocked for ease of management. Two grazing experiments were therefore imposed on lucerne stands to quantify the effect of spring grazing management treatments on the animal and plant production, particularly the persistency of the lucerne stand through the perennial reserves composition and quantity. The overall liveweight gains were similar between treatments with rotational having 894 kg LW/ha, semi set-stocked 881 kg LW/ha, and set-stocked having 890 kg LW/ha. The rotational treatments total dry matter production was 12,106 kg DM/ha. Plant population was the highest under set-stocked treatments with 206 plants/m², but it also had the biggest decline, to 134 plants/m² in May. The rotational treatments had the highest total root weights across all treatments, with 4,682 kg/ha, compared to semi set-stocked and set-stocked with 3,443 and 3,989 kg/ha, respectively. Although liveweight gains between treatments were similar, the carbon and nitrogen reserves in the rotational treatments were higher than semi set-stocked and set-stocked treatments. This implies that the persistence of the rotational stand will be greater than the semi set-stocked and set-stocked stands. However, results suggest that set-stocking for a short period of time (e.g. a month) is possible over spring provided that lucerne growth exceeds demand.

This dissertation is a study of the construction of meaning below the word level, specifically how roots and morphemes combine to create verbs, and the contribution of each to the meaning that a verb construes. It uses data from the verb system of Modern Standard Arabic to bring together the theory that roots combine with different structures to produce verbs describing different types of event, and the observation that many roots cannot form verbs on their own, and must combine with other morphemes do to so. The thesis is that Arabic roots lexicalize events, states or things, but remain free to create new meaning in combination with the different verb stems of Arabic, each of which contains one or more morphemes that determine the type of event that a root may come to describe. The findings are that the morphemes present in the different verb stems of Arabic condition verb meaning in four main ways: through reflexivization; through providing an Actor subject argument; through marking plural event phases; and through marking the presence of two relations construed as one event. A root combines with a morpheme that determines the type of event that a verb may describe, and it contributes meaning within the limits set by that morpheme. Thus morphemes do not modify a fixed concept, but root and morpheme create verb meaning together. The implication of this for a theory of meaning below the word level is that the semantic concepts which humans communicate remain relatively constant, but they are expressed at different levels of granularity: at the root level; by combining roots below the word level; by combining roots with morphemes below the word level; and by combining words at the clause level. This opens up avenues for further research to establish the differences, if any, between the meanings construed at these different levels of granularity.

A paradigm shift from maximum to sustainable agricultural production also applies to cultivation of bioenergy crops. Nitrogen (N) fertilization is needed to sustain the biomass yield of switchgrass as a biofuel feedstock and, consequently, may influence the potential for soil quality improvement through soil organic carbon (SOC) sequestration. Because changes in soil quality can feed back to affect the sustainability of biomass production, the impacts of N application on switchgrass biomass production and soil quality need to be evaluated together. Therefore, the overall objective of this study was to assess the effects of N fertilization on switchgrass biomass, changes in SOC concentration and pool, and soil structural properties. This objective was realized by conducting field experiments in Ohio and Tenessee, and a laboratory incubation study in Ohio. The aboveground biomass of switchgrass was more strongly influenced by N fertilization than the belowground biomass. Even when the aboveground biomass was harvested and removed, N fertilization led to an increase in SOC, both in Ohio and Tennessee. The data from laboratory incubation study showed that N additions could retard the decomposition of organic matter, which may contribute towards higher SOC pools in N fertilized plots. The results from the Tennessee experiments indicated the important role of roots in stabilizing soil structure. Despite higher SOC concentrations in plots receiving a high rate of N fertilization, higher soil structural stability was associated with greater root biomass and longer root length in plots receiving none or a low rate of N fertilizer. These data indicated that root growth is a crucial driver of surface soil structure.

The objective of this research was to identify genes involved in ethylene-auxin crosstalk that are required to maintain wild-type ethylene signaling and response in the roots but not hypocotyls of Arabidopsis seedlings. Using this root-specific phenotype, two genes related to Indole-3-Acetic Acid (IAA) biosynthesis were identified that are required for proper ethylene response. WEAK ETHYLENE INSENSITIVE7 (WEI7) codes for the beta subunit of anthranilate synthase, which catalyzes the first committed step in the tryptophan biosynthesis pathway, the conversion of chorismate to anthranilate, a tryptophan, therefore, IAA precursor. WEAK ETHYLENE INSENSITIVE8 (WEI8) codes for an aminotransferase, which is believed to convert tryptophan to indole-3-pyruvic acid (IPA) in the IAA biosynthesis pathway. WEI7 works in conjunction with WEI2 (the anthranilate synthase α-subunit protein) and both are up-regulated by ethylene and responsible, at least in part, for the ethylene-mediated stimulation of auxin biosynthesis. This increase in IAA then is required for a normal response to ethylene in the root. Since tryptophan treatments do not induce auxin phenotypes of elongated hypocotyls and epinastic cotyledons in Arabidopsis, this regulatory scenario is likely to exist for other genes of the tryptophan and IAA biosynthesis pathway, such as WEI8. wei8, a loss of function mutant of an auxin biosynthetic gene, results in root-specific ethylene insensitivity. WEI8 has aminotransferase activity in vitro, can use tryptophan as a substrate, and therefore, it could be responsible for the in vivo conversion of tryptophan into IPA. Double mutant studies support this model. When wel2, a mutant of the WEI8 homolog, WEL2, is used to generate wei8 wel2 double mutants, auxin defects such as agravitropism and loss of apical dominance were seen. Double mutant seedling roots were agravitropic, and adult plants had severe loss of apical dominance as well as reduction in fertility due to defects in flower anatomy. Additionally, analysis of the auxin reporter DR5-GUS expression suggests that WEI8 is required for maintaining normal levels of auxin in the roots of Arabidopsis. WEI7 and WEI8 regulate IAA production and are unexpected interaction points between ethylene response and IAA biosynthesis. Identification of these genes will enable further research on the role of specific pathways of IAA biosynthesis in different tissues and during specific developmental programs. Moreover, it will contribute to a better understanding of hormonal crosstalk in plants.

The following is a collection of original poetry. The manuscript consists of an introduction explaining influences and style, and four chapters of poems categorized by subject matter: object/nature, writing/creativity, relationships, and family/figures. INDEX WORDS: Poetry, Poem

Soybeans (Glycine max L. Merr.) are a very important source of edible oil in the U.S. Palmitic acid (16:0) is the major saturated fatty acid present in soybean oil and it has been linked to increased risk of coronary diseases. Soybean oil typically contains 110g kg-1 of palmitic acid and it is desirable to decrease its content to 40 g kg-1. To accomplish this objective it is important to study the target genes that control the production of fatty acids in the biosynthetic pathway, involved in de novo fatty acid biosynthesis and triacylglycerol assembly. It is known that at least five recessive alleles condition the low palmitic acid contents of soybean seeds: fap1, fap3, fap*, fapnc and sop1. The fapnc mutation affects the normal function of the enzyme 16:0-ACP thioesterase encoded by the gene FATB1. There are four FATB1 isoforms in soybean: GmFATB1a, GmFATB1b, GmFATB2a, and GmFATB2b. GmFATB1a is deleted in N97-3681-11 and N97-3708-13 lines homozygous for the fapnc mutation, and specific markers were developed for this isoform. The GmFATB1a specific marker accounted 62 to 70% of the genotypic variation in palmitic acid content in two F4 derived populations. It is 100% linked to the locus of interest and should be very useful in marker-assisted selection programs designed to lower the palmitic acid levels of soybean oil. Linolenic acid (18:3) contains three double bonds and is particularly susceptible to oxidation. There are at least three major loci responsible for low 18:3 content in soybean seed oil (fan, fan2 and fan3), and possibly 2 more loci if the fanx allele and the low 18:3 allele from N78-2245 are also independent loci. By decreasing the 18:3 content of soybean oil from its typical level to a level of 30 g kg-1, it may be possible to eliminate or reduce the need for hydrogenation of the oil. The FAD3 gene encodes an omega-3 desaturase that converts 18:2 to 18:3 in the endoplasmic reticulum. It has four highly similar microsomal isoforms: GmFAD3A and GmFAD3B (93% DNA identity shared), FAD3-2a and FAD3-2b. A single polymorphism was confirmed for the GmFAD3A gene when cDNA sequences from 6 soybean parental lines used in our segregating populations were compared. A random SNP in intron 2 of the GmFAD3A gene isoform was discovered in Boggs, PI123440, and the two low linolenic parental lines in our populations. We have developed a CAPS marker that distinguishes the GmFAD3A allele inherited from PI123440. The segregation at this locus explained 77.5 to 89.2% of the genotypic variation in linolenic acid content in two F4 derived populations. The root and leaf tissue fatty acid composition of two lines carrying the fapnc, fap1, and fan(PI123440) alleles and of a genetically related high yielding normal line, Brim was examined to determine if these mutations were also expressed in those tissues (pleiotropy). We concluded that fapnc or fap1 or both mutations have pleiotropic effects on the leaf fatty acid composition. Therefore, leaf membranes such as chloroplast membranes could be affected and those changes could affect their physiological behavior, representing a likely explanation for the yield drag observed in lines carrying the fapnc mutation. The fan mutation also has pleiotropic effects on the leaf and root fatty acid composition but has not been negatively correlated with yield. Our future efforts will be to map this GmFAD3A gene in these populations and compare their genomic location with the fan locus and QTL associated with linoleic acid content.

The formation of the root epidermis in Arabidopsis provides a simple and elegant model for the study of cell fate specification. An epidermal cell develops as a root hair cell when it overlies two cortical cells, and develops as a root non-hair cell when it overlies a single cortical cell. A network of transcription factor proteins, WEREWOLF (WER), GLABRA3 (EGL3), ENHANCER OF GLABRA3 (EGL3), and TRANSPARENT TESTA GLABRA1 (TTG1), promote the non-hair cell fate through the activation of GLABRA2 (GL2) gene expression in the non-hair cell position, and promote the hair cell fate through the activation of CAPRICE (CPC) gene expression in the non-hair cell position. The CPC protein acts through a mechanism of lateral inhibition to regulate gene expression in the neighboring hair cells by the direct movement of the CPC protein from non-hair cells to hair cells and throughout the epidermis. We have identified four CPC homologs, TRIPTYCHON (TRY), ENHANCER OF TRY AND CPC 1, 2 and 3 (ETC1, ETC2 and ETC3), that are able to functionally substitute for the CPC in root epidermal patterning. CPC, TRY and ETC1 are expressed in the non-hair cell position and act in a partially redundant manner to regulate cell fate specification in the root, whereas ETC2 and ETC3 are not expressed in the root and do not have a role in root epidermal patterning. We identify a new regulator of root epidermal patterning, TRANSPARENT TESTA GLABRA2 (TTG2), that enhances a cpc mutant phenotype. We find that the TTG2 and GL2 and genes positively regulate TRY gene expression, but do not regulate CPC or ETC1 gene expression in the non-hair cell position. Thus, we propose that TTG2 and GL2 act in a secondary step to initiate and maintain lateral inhibition signaling through the regulation of TRY gene expression in the root epidermis.

A mechanistic understanding of crop-weed interaction has been used in dynamic simulation models of the growth of crop-weed mixtures to estimate the outcomes of competition, including yield losses, and predict the effects of management practices. In the case of an annual crop such as maize, when plants in mixtures begin to compete for light during the early growing season, the relative position of the leaves of the crop and weeds determine the light captured by the plant and its subsequent growth and yield. Thus the total area and distribution of leaves, and factors that can change those characteristics will impact crop competitiveness. Below ground resources such as nitrogen or water availability, are thought to be among those factors that influence leaf area and distribution. However due to the complexity of studying competition for below ground resources, little information has been gathered to support this assumption. The specific objectives of the present study are: i) to characterize early season root system growth for maize and four weed species and to determine the effects of above and belowground maize competition on maize and weed root system development; ii) characterize, in comparison with maize, the early and exponential growth phases of four weed species; iii) identify and quantify the changes induced by nitrogen stress in plant architecture and morphology that could be important in determining weeds and maize success in compete for resources in a mixed maize-weed stand. To achieve the first objective, this study utilized an herbicide injection technique to assess the comparative root geometries and temporal development patterns for redroot pigweed (Amaranthus retroflexus L.) and velvetleaf (Abutilon theophrasti Medic.) in association with maize (Zea mays L.); and redroot pigweed, velvetleaf, maize, common lambsquarters (Chenopodium album L.) and giant foxtail (Setaria faberi Herm.) in monoculture. The second and third objectives were addressed in a separate glasshouse experiment where maize, A. retroflexus, A. theophrasti, S. faberi and C. album where grown in sand culture at varying soil solution nitrogen levels (0.2, 0.5, 2, 5 mM L-1 NO3). Root system vertical and lateral growth was more variable among species than between different soil types, suggesting that root development in the absence of important soil physical impediments is a plant intrinsic characteristic. For A. theophrasti and A. retroflexus, root system volume was proportional to plant above-ground biomass. Thus, plants growing under a competitive environment and having reduced above-ground biomass have a proportionally smaller root system, potentially compromising their ability to capture and compete for soil resources with their neighbors. This study also provides insights into the likelihood of belowground competition occurring between plants based on the likelihood of root system overlapping and exploring the same soil regions. Increasing levels of soil nitrogen significantly increased relative above-ground plant biomass in a similar fashion for maize and the three broadleaf weeds, but S. faberi was comparatively unresponsive to higher levels of soil nitrogen. Diverse growth sensitivities to soil nitrogen may in part explain the variability of competitive relationships commonly observed under field conditions. Our results demonstrate that species do not respond uniformly to changes in soil nitrogen status and those differential responses must be addressed when considering the impact of soil fertility on competitive outcomes in agricultural systems. Furthermore, the root development study indicated that the chance of a crop-weed mixture exploiting a common region of soil or finding an enriched patch of soil are low at the early growth stages, suggesting that localized differences in nitrogen availability could drive the competitive relationship in favor of the crop or the weeds.

Wasabi (Wasabia japonica (Miq.) Matsum) is an aromatic herb that adds a sharp hot taste and pungent smell to food and, therefore, is highly appreciated in Japanese cuisine. Recently wasabi has emerged as a new flavour in western cuisine. The unique flavour of wasabi comes from the isothiocyanate (ITC) content which is the key quality parameter of wasabi. This research was performed to investigate the factors which affect the ITC profile in wasabi, as a way to support the emerging wasabi industry in New Zealand. The present study highlighted the existence of a misconception concerning the flavour difference between wasabi and horseradish. Wasabi is known as Japanese horseradish, but differs in its ITC profile compared to European horseradish. The key indicator is 2-phenylethyl ITC, which is found only in European horseradish and gives it a radish like flavour. Thus, it is very important for processors to understand the differences in ITC profile between wasabi and horseradish to manufacture a product which has a unique wasabi flavour. Seven ITCs have been investigated in New Zealand grown wasabi and, among them, allyl ITC was the most abundant ITC, contributing 86-94% of the total ITC concentration. 3-butenyl ITC and 4-pentenyl ITC made up 3-8% of the total ITC while the other ITCs (iso-propyl ITC, isobutyl ITC, sec-butyl ITC, 5-hexenyl ITC) contribute very small amounts to the total ITC content. The two cultivation methods (soil and water) showed no variation in ITC yields of larger rhizomes (>45 g). In soil cultivated plants, ammonium sulphate fertiliser (containing 21 % N with 24% S) was very effective in significantly increasing ITC yields from 2316 mg/kg to 3366 mg/kg (a 45% increase of allyl ITC in the rhizomes compared to the control level) when applied at a rate of 200 kg N /ha. This treatment also highlighted the importance of N and S nutrients for ITC synthesis in wasabi, as both N and S are components of ITCs and the precursor glucosinolates (GSLs). A 61-77% increase of ITC yield was also observed in the rhizomes when the plants commenced flowering after 18 months of growth. Consequently, this result suggests that flowering is an important event in the crop management process. Among the four plant parts of wasabi, rhizomes yielded the highest level of all ITCs and traditionally this is the most important plant part. Other parts like petioles and leaves gave lower yields of ITCs, but could be used when lower concentration of ITCs are required in the final product. The larger rhizome, the outer layer and distal portion of the rhizome had a higher ITC yield than smaller rhizomes, the inner tissues and proximal portion of the rhizome respectively. Suitable storage conditions for rhizomes are very important to retain the quality of the raw materials and, therefore, products. This research showed that defrosting can potentially lead to large losses of ITCs from frozen rhizomes. For example, a 99.7% loss of allyl ITC was observed after 16 days when snap frozen rhizomes were defrosted slowly at 4°C. Storage at -10°C or lower temperatures (up to -80°C) for two months retained the original ITC levels in the rhizomes. The shelf life analysis of allyl ITC in mayonnaise-type sauces containing wasabi oil (4400 mg of total ITC/kg of oil) gave a life of 8-9 weeks (considering 5% loss of allyl ITC to be the end of satisfactory storage) when stored at between 4 to 30°C. Shelf life was reduced to less than 2 weeks for a tomato based sauce prepared with a lower amount of wasabi oil, higher water content and heat treated by pasteurisation at 90°C for 30 minutes under the same storage conditions. Overall the data obtained from this study will assist farmers and processors to produce high quality products using recently introduced wasabi crop in New Zealand.

The response of grape (Vitis vinifera L.) plants to various nitrogen environments (104 ppm N and 10.4 ppm N) were studied. Grape plants were grown in continuously circulated nutrient solution in a temperature and ventilation controlled glasshouse. Dry weights of roots, stems, shoots and leaves were measured, as well as root length, root number, shoot length, leaf area and leaf number. No significant differences were obtained between nitrogen levels, however, trends were obtained to suggest that grapes respond to increasing nitrogen nutrition in terms of growth and morphological adaptation in a similar way to other plant species. The lack of significance can possibly be associated with large plant variation, increased nitrogen supply due to convective and diffusive mechanisms related to hydroponics, and the possibility that the experiment was too short to see differences created by each nitrogen level. Further work needs to be be carried out under a modified method in order to elicit a significant response of grapes to environmental stress in the form of low nitrogen levels.

This has been a co-operative research project between the Ministry of Agriculture and Fisheries, Division of Horticulture and Processing, DSIR, New Zealand Apple and Pear Marketing Board, The New Zealand Fruit growers Federation and the Department of Horticulture, Lincoln University commenced in the winter of 1986. The objective was to monitor 15 Royal Gala or Gala apple orchards in the three main apple producing regions of New Zealand to produce a data base for modelling biological and financial interactions. Selected trees were continuously monitored for three growing seasons. One orchard was continuously monitored for another 3 years (in the third additional year for the purpose of model validation). The orchards were 5 - 8 years old during the first monitoring season. Twelve of the orchards were on MM106 rootstock and the remainder on M793. Tree density ranged from 455 - 1102/ha. Five trees were monitored for fruit number and fruit quality in each orchard at harvest. Three branches from each monitored tree were chosen to record the number of flowers and fruits before thinning and after thinning. To establish a fruit tree branch sampling system which can be reliably extrapolated to a whole tree basis, measurements from 204 trees, 151 parent branches and 9283 sub-branches were involved. Wood density was measured and the estimation of the volume of a branch, and the ratio of the branch to the whole tree, compared. Evidence is presented to show that the ratio of the sum of branch cross sectional area (CSA) to the trunk CSA is equal to the ratio of fruitfulness of the whole tree to fruitfulness of the sum of the branches. A relationship has been established between the sum of the CSA of branches directly arising from the central leader and the trunk CSA of central leader-trained apple trees. Ratios of 1.6 - 2.1 : 1 have been determined over 7 years of research without any major influence from pruning. The relationship of secondary branching of individual fruiting arms was investigated also, suggesting a similar relationship between branch CSA and secondary branch CSA but the influence from pruning, in this case, is relatively greater. Between orchard, tree and branch variation is explained. Recommendations on branch sampling for research and monitoring purposes are provided, based on these findings. Climatic data from 7 meterological stations was used, incorporating temperature, sunshine hours and rainfall. For each season the orchards were monitored, climatic data was recorded for the period October in the previous growing season until harvest time (March) of the current season, a total of 18 months in each case. Correlation calculations were attempted for all monthly combinations. Contour maps of correlation coefficients between tree parameters and monthly combinations of climatic data are presented to show the major effects of climate on fruit production. The production of multiple regressions has been focused on a range of tree parameters, with relevant climatic data from the contour maps added, to refine the mathematical relationships. Higher maximum temperatures in the period of March and April produced higher initial fruit set (r = 0.54**) the following spring suggesting an effect on quality of the flower. Lower maximum temperatures in the late dormant period (August to September) produced a higher initial fruit set (r = -0.40**) as well. The natural simple regression between initial fruit set and flower number per cross sectional area (CSA) gives an r value of -0.47** indicating that the more flowers on a tree the lower the percentage initial fruit set. Introduction of the climatic effects produces a refined multiple regression with an r value at 0.76**. A negative correlation for estimating fruit number/ha after thinning was determined (r = -0.78**). The estimation of fruit volume from fruit diameter was explored. Fruit growth curves based on fruit diameter or volume were plotted for 2 growing seasons. The influence of temperature on fruit growth is documented. Fruit size variation was explored and the sampling size for estimating average fruit weight is recommended. It is demonstrated how fruit number after thinning can be extrapolated to estimate total yield, fruit size and size distribution at harvest. Average fruit size was positively correlated with November to February temperatures in the previous season and also maximum temperatures in the December to January period prior to harvest. A negative correlation with fruit size was found for minimum temperatures in May. All these improved knowledge on the relationship between average fruit size and fruit number after thinning, but the maximum temperatures in December and January were critical in providing more accurate information (r = 0.81**) for harvest predictions. For management planning it is necessary to relate yield, fruit quality and size distribution, revenue and cost data, in order to calculate annual gross margins. A set of dynamic mathematical models developed are presented, to demonstrate the interrelationship of factors influencing apple production and profitability. Based on the model, a computer program was produced for practical orchard application. At the blossom and pre-thinning stages of fruit production, model users may specify parameters recorded from their own trees (eg flower numbers) and climatic data to predict tree behaviour for the next stage. At the post-thinning stage, model users may again specify parameters recorded from their own trees (eg fruit number) and climatic data to predict yield and fruit size distribution at harvest. These predictions can be correlated with financial data such as price realisations for the fruit and production and harvesting costs, to minimise estimated net return. The models allow annual climatic data to be balanced against biological parameters (eg fruit number) in order to minimise costs and maximise gross income and annual gross margins. For example, the required fruit number per tree after thinning can be correlated with the size grade distribution which will maximise returns, incorporating weather, cost and other key management parameters. Carbohydrate reserves in the dormant period are of primary importance for fruit production in the following year. The storage of starch in different parts or organs of apple trees was compared. The concentration of starch in the root system is much higher than that in the above ground parts. Observations of root growth and photos provided the evidence that roots continued to grow in the dormant period in Canterbury. Non-structural young rootlets contained almost no starch. For secondary roots, on average, thin roots contained higher concentrations of starch than thicker roots. However, results indicated there is greater variation of starch concentration in thinner roots. Results also showed that the starch content in root bark is much higher than that in root wood. The sampling variation may be reduced when bark and wood are separately tested. This is because the ratio of bark to wood is different for different roots. To minimize the variation, the bark of roots above 1 cm in diameter is recommended for analysis. Under 3 different crop loads, starch content was measured using replicates of 6 roots per tree and 3 trees per treatment. Starch content under light crop load conditions was significantly higher than that of middle and high crop loads, indicating a negative correlation with crop load in the growing season. A negative relationship between the content of starch and soluble sugar was found, reflecting the vigour of root growth. For the following year's production, higher yield or fruit number was positively correlated with the stored starch level or negatively correlated with the yield or fruit number in the previous growing season. An accurate method of estimation of fruit size distribution using average fruit weight and standard deviation of the mean is discussed.

The response of cucumber (Cucumis sativus L.) plants to various root and shoot environments (solution depth, temperature, ionic strength, nitrogen and calcium level and light intensity) were studied. Cucumber plants were grown in continuously circulating-solution in a heated-glasshouse. Dry weights of leaves, stems and roots, leaf area, leaf number, root length and root number were measured as well as uptake of potassium, calcium and nitrogen. The relationship between shoot and root in terms of functional equilibrium equations was also examined. The results presented show that: 1. Shoot growth of cucumber plants was reduced if grown in solutions of less than 50mm in depth; 2. When roots were grown in shallow solution depths at 1 or 5mm the dry weight allocated to the root increased. The ratio of root number/root length(no./cm) also increased. Lowering solution temperature to 12.5±2.5°C enhanced the production of root number relctive to root length, and 5 and 2% of full strength and 5% of full strength nitrogen level solution stimulated the growth of root length relative to root number; 3. Under low solution temperature treatment leaf number was maintained at the expense of leaf area. Under low total ionic strength and low nitrogen solution, enhanced root length growth was at the expense of leaf area growth; 4. Low solution temperature enhanced the dry weight allocated to the stem relative to the leaf. Low total ionic strength and low nitrogen solution increased the dry weight allocated to the leaf relative to the stem; 5. The specific activity of root, represented by specific absorption rate, increased when the shoot was under light stress and, the specific activity of shoot, represented by unit shoot rate, increased when the root was under nitrogen-stress; 6. The form of equation developed by Thornley (∆M = fm∆W, where ∆M is the increment in weight of element M and ∆W the increment in total plant dry weight during a time period ∆t with fm a constant) showed a better relationship than the equation developed by Davidson [root mass x rate(absorption) ∝ leaf mass x rate(photosynthesis)] and subsequently used by Hunt in the form of mass ratio(root/shoot) ∝ l/activity ratio; 7. The equation developed by Chung et al, total plant weight/(leaf number/leaf area) ∝ total "k"/(root number/root length), where k represents the total contents of elements or compounds, showed a good approximation of the relationship between shoot and root under all the environmental stresses imposed with the exception of calcium uptake. The results support the concept that the activity of the root or shoot in carrying out its function is influenced by the demand created by the opposite organ and appears to be a better assumption than that which proposes that the activity of an organ is solely dependent on its own size.

TD-54 A Thesis presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Forestry, Fisheries and Wildlife, Under the Supervision of Professor Ronald M. Case. Lincoln, Nebraska: December, 1992. Copyright (c) 1992 Bruce A. Jasch