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An Overview Of Plant Defenses Against Pathogens And Herbivores, Brian C. Freeman, Gwyn A. Beattie 2016 Iowa State University

An Overview Of Plant Defenses Against Pathogens And Herbivores, Brian C. Freeman, Gwyn A. Beattie

Gwyn Beattie

Plants represent a rich source of nutrients for many organisms including bacteria, fungi, protists, insects, and vertebrates. Although lacking an immune system comparable to animals, plants have developed a stunning array of structural, chemical, and protein-based defenses designed to detect invading organisms and stop them before they are able to cause extensive damage. Humans depend almost exclusively on plants for food, and plants provide many important non-food products including wood, dyes, textiles, medicines, cosmetics, soaps, rubber, plastics, inks, and industrial chemicals. Understanding how plants defend themselves from pathogens and herbivores is essential in order to protect our food supply and ...


Habitat Temperature And Precipitation Of Arabidopsis Thaliana Ecotypes Determine The Response Of Foliar Vasculature, Photosynthesis, And Transpiration To Growth Temperature, William W. Adams III, Jared J. Stewart, Christopher M. Cohu, Onno Muller, Barbara Demmig-Adams 2016 University of Colorado Boulder

Habitat Temperature And Precipitation Of Arabidopsis Thaliana Ecotypes Determine The Response Of Foliar Vasculature, Photosynthesis, And Transpiration To Growth Temperature, William W. Adams Iii, Jared J. Stewart, Christopher M. Cohu, Onno Muller, Barbara Demmig-Adams

Ecology & Evolutionary Biology Faculty Contributions

Acclimatory adjustments of foliar vascular architecture, photosynthetic capacity, and transpiration rate in Arabidopsis thaliana ecotypes (Italian, Polish [Col-0], Swedish) were characterized in the context of habitat of origin. Temperatures of the habitat of origin decreased linearly with increasing habitat latitude, but habitat precipitation was greatest in Italy, lowest in Poland, and intermediate in Sweden. Plants of the three ecotypes raised under three different growth temperature regimes (low, moderate, and high) exhibited highest photosynthetic capacities, greatest leaf thickness, highest chlorophyll a/b ratio and levels of β-carotene, and greatest levels of wall ingrowths in phloem transfer cells, and, in the Col-0 ...


Multicellular Secretory Trichome Development On Soybean And Related Glycine Gynoecia, R. A. Healy, R. G. Palmer, Harry T. Horner 2016 Iowa State University

Multicellular Secretory Trichome Development On Soybean And Related Glycine Gynoecia, R. A. Healy, R. G. Palmer, Harry T. Horner

Harry Horner

Multicellular glandular trichomes form on gynoecia of wild annual Glycine species, annual soybean cultivars, and wild perennial Glycine species. These trichomes occur from the ovary base to the style base and, in perennial species, along the style as well.Trichomes form at least 2 d before anthesis, and new trichomes develop throughout flowering and also on young seed pods. Trichome structure is similar in all taxa examined, usually five to seven linearly arranged cells. Stalk cells with callose walls become highly vacuolate, and their cytoplasms have reduced numbers of Golgi bodies and endoplasmic reticulum. During secretion, two to four distal ...


Structural Adaptations In Overwintering Leaves Of Thermonastic And Nonthermonastic Rhododendron Species, Xiang Wang, Rajeev Arora, Harry T. Horner, Stephen L. Krebs 2016 Iowa State University

Structural Adaptations In Overwintering Leaves Of Thermonastic And Nonthermonastic Rhododendron Species, Xiang Wang, Rajeev Arora, Harry T. Horner, Stephen L. Krebs

Harry Horner

Evergreen rhododendrons (Rhododendron L.) are important woody landscape plants in many temperate zones. During winters, leaves of these plants frequently are exposed to a combination of cold temperatures, high radiation, and reduced photosynthetic activity, conditions that render them vulnerable to photooxidative damage. In addition, these plants are shallow-rooted and thus susceptible to leaf desiccation when soils are frozen. In this study, the potential adaptive significance of leaf morphology and anatomy in two contrasting Rhododendron species was investigated. R. catawbiense Michx. (native to eastern United States) exhibits thermonasty (leaf drooping and curling at subfreezing temperatures) and is more winter-hardy [leaf freezing ...


Formation Of Calcium Oxalate Crystals Associated With Apothecia Of The Discomycete Dasyscypha Capitata, Harry T. Horner, Lois H. Tiffany, Anita M. Cody 2016 Iowa State University

Formation Of Calcium Oxalate Crystals Associated With Apothecia Of The Discomycete Dasyscypha Capitata, Harry T. Horner, Lois H. Tiffany, Anita M. Cody

Harry Horner

Calcium oxalate dihydrate crystals form at or near the tips of sterile hairs on the apothecia of the oak leaf litter discomycete Dasyscypha capitata. Early in their development, the crystals appear to be covered by a wall or membrane, whereas later they appear external. The crystals on each hair form a mass of crystals called a druse. Quite often the smaller crystals near the apex of the tip form a rosette, whereas the more peripheral crystals are much larger and display shapes possibly related to environmental factors. The formation and development of Dasyscypha crystals are compared with recent studies of ...


Floral Nectary Fine Structure And Development In Glycine Max L. (Fabaceae), Harry T. Horner, Rosaria A. Healy, Teresa Cervantes-Martinez, Reid G. Palmer 2016 Iowa State University

Floral Nectary Fine Structure And Development In Glycine Max L. (Fabaceae), Harry T. Horner, Rosaria A. Healy, Teresa Cervantes-Martinez, Reid G. Palmer

Harry Horner

Floral nectaries of annual cultivated Glycine max develop between the bases of the central gynoecium and lateral stamen ring. Each discoid nectary forms immediately before flower opening and degenerates within 24 h. Three stages of nectary development are identified: preactive, active, and postactive. Preactive and active nectaries are composed of a single-layered epidermis that contains many open stomata, with guard cells having thickened walls, starch-engorged plastids, and other organelles. The major portion of each nectary consists of thin-walled special parenchyma cells, each having dense cytoplasm with a nucleus, Golgi bodies and vesicles, mitochondria, plastids, endoplasmic reticulum, many ribosomes, and one ...


A Microscopic Study Of The Trichomes On Gynoecia Of Normal And Tetraploid Clark Cultivars Of Glycine Max And Seven Near Isogenic Lines, Rosaria A. Healy, Harry T. Horner, Theodore B. Bailey, Reid G. Palmer 2016 Iowa State University

A Microscopic Study Of The Trichomes On Gynoecia Of Normal And Tetraploid Clark Cultivars Of Glycine Max And Seven Near Isogenic Lines, Rosaria A. Healy, Harry T. Horner, Theodore B. Bailey, Reid G. Palmer

Harry Horner

The surfaces of gynoecia of Glycine max cultivars—normal Clark, a tetraploid Clark, and seven isolines—display variations in at least three types of trichomes. The normal Clark soybean gynoecium has at least three and possibly four types of trichomes: a two‐ to four‐celled, elongate, thick‐walled trichome (TWT), an elongate thin‐walled unicellular trichome (UCT), a secretory multicellular trichome (MCT), and an elongate thin‐walled bicellular trichome that we have interpreted as an immature TWT. All these types are present on the gynoecium by 1 d before anthesis. After fertilization, the UCT is rare, but the other types ...


Ascorbic Acid: A Precursor Of Oxalate In Crystal Idioblasts Of Yucca Torreyi In Liquid Root Culture, Harry T. Horner, Albert P. Kausch, Bruce L. Wagner 2016 Iowa State University

Ascorbic Acid: A Precursor Of Oxalate In Crystal Idioblasts Of Yucca Torreyi In Liquid Root Culture, Harry T. Horner, Albert P. Kausch, Bruce L. Wagner

Harry Horner

Liquid-cultured primary roots of Yucca torreyi L. (Agavaceae), which are similar to its intact roots, develop uninterrupted files of calcium oxalate crystal idioblasts with raphide bundles in their cortex, beginning just proximal to the terminal meristem. Each single file of idioblasts displays a basipetal ontogenetic sequence. [1-14C]glycolic acid, [1-14C]glyoxylic acid, and L-[1-14C]ascorbic acid, all of which are potential precursors of oxalate, were each added to different flasks that contained a sterile liquid medium and isolated roots and were allowed to interact with the roots for 45 min. After thorough washing, the roots grew for periods that ...


Evolution And Systematic Value Of Leaf Crystal Macropatterns In The Genus Peperomia (Piperaceae), Harry T. Horner, Stefan Wanke, Marie-Stephanie Samain 2016 Iowa State University

Evolution And Systematic Value Of Leaf Crystal Macropatterns In The Genus Peperomia (Piperaceae), Harry T. Horner, Stefan Wanke, Marie-Stephanie Samain

Harry Horner

Leaves of Peperomia species vary in texture, shape, succulence, lamina size, thickness, coloration, and venation. Each leaf contains only calcium oxalate druses in palisade cells, druses in palisade and raphides in spongy parenchyma, or druses in palisade and prisms in spongy parenchyma. Collectively, these variations create distinct crystal macropatterns. Leaves from 45 species were studied to identify their macropatterns and to compare the macropatterns with molecular data. Microscopic data showed two major crystal macropatterns and five variations of them. All but one species displayed either a single druse in most palisade cells forming one or more uniform crystal layers (81 ...


Insect-Mediated Cross-Pollination In Soybean [Glycine Max (L.) Merrill]: Ii. Phenotypic Recurrent Selection, Evelyn Ortiz-Perez, Hunt Wiley, Harry T. Horner, William H. Davis, Reid G. Palmer 2016 Universidad Autonoma de Nuevo Leon

Insect-Mediated Cross-Pollination In Soybean [Glycine Max (L.) Merrill]: Ii. Phenotypic Recurrent Selection, Evelyn Ortiz-Perez, Hunt Wiley, Harry T. Horner, William H. Davis, Reid G. Palmer

Harry Horner

Recurrent selection is a method for population improvement which has been used in soybean [Glycine max (L.) Merrill] to modify traits such as grain yield, seed-protein content, seed-oil content, tolerance to iron-deficiency chlorosis, and seed size. Nuclear male-sterility with insect-mediated cross-pollination has been successfully used in recurrent selection schemes in soybean. However, little attention has been given to selection to increase the agronomic performance of male-sterile plants per se. The objective of this study was to evaluate the response of male-sterile lines segregating for male-sterile alleles ms2, ms3, ms6, ms8, and ms9 to phenotypic recurrent selection for increased seed-set after ...


Oak-Leaf-Litter Rhizomorphs From Iowa And Texas: Calcium Oxalate Producers, Harry T. Horner, Lois H. Tiffany, George Knaphus 2016 Iowa State University

Oak-Leaf-Litter Rhizomorphs From Iowa And Texas: Calcium Oxalate Producers, Harry T. Horner, Lois H. Tiffany, George Knaphus

Harry Horner

Unidentified basidiomycete rhizomorphs growing on oak-leaf litter {Quercus alba) in Iowa and in Texas {Quercus gravesii) displayed arrays of crystals associated with their hyphae. X-ray diffraction and birefringence analyses identified the crystals as a mix- ture of calcium oxalate-monohydrate and -dihydrate. The Iowa oak-leaf-litter rhizomorph crystals occurred in two forms: young hyphae displayed either small styloid-like crystals oriented in all directions along the hyphae; or large clusters of elongated styloid-like crys? tals surrounding the hyphae, with individual crystals in each cluster displaying pyramidal ends. Crystals as? sociated with the Texas oak-leaf-litter rhizomorphs consistently covered all of the young hyphae and ...


Macropattern Of Styloid And Druse Crystals In Quillaja (Quillajaceae) Bark And Leaves, Nels R. Lersten, Harry T. Horner 2016 Iowa State University

Macropattern Of Styloid And Druse Crystals In Quillaja (Quillajaceae) Bark And Leaves, Nels R. Lersten, Harry T. Horner

Harry Horner

Quillaja has been shuffled among tribes and subfamilies of Rosaceae, segregated from it as a separate family, and, most recently, transferred to the Fabales as a separate family. Many anomalous characters have kept it from being settled anywhere permanently. One character never mentioned by systematists, but long known, is the anomalous (for Rosaceae) occurrence of prominent styloid calcium oxalate crystals, reported from the inner bark of stems. We describe in more detail the macropattern of crystal distribution in stem and leaf, using vibratome sections, sodium hypochlorite clearings of leaves, and polarizing and scanning electron microscopy. Styloids are extremely numerous in ...


Insect-Mediated Seed-Set Evaluation Of 21 Soybean Lines Segregating For Male Sterility At 10 Different Loci, E. Ortiz-Perez, Harry T. Horner, S. J. Hanlin, R. G. Palmer 2016 Iowa State University

Insect-Mediated Seed-Set Evaluation Of 21 Soybean Lines Segregating For Male Sterility At 10 Different Loci, E. Ortiz-Perez, Harry T. Horner, S. J. Hanlin, R. G. Palmer

Harry Horner

The first requirement to establish a successful hybrid soybean program is the availability of a stable male-sterile, female-fertile system. Male sterility has been an important tool in soybean breeding programs to improve traits such as yield, seed-protein and seed-oil content, and seed size. However, improvement of seed-set per se on male-sterile plants has not been an important breeding objective. The evaluation of the out-crossing potential of the available male-sterile, female-fertile soybean lines is crucial to determine the future of hybrid soybean. The objective of this study was to evaluate seed-set among 21 soybean lines segregating for male sterility at 10 ...


The Capacity Of Switchgrass (Panicum Virgatum) To Degrade Atrazine In A Phytoremediation Setting., Ian J. Murphy, Joel R. Coats 2016 Iowa State University

The Capacity Of Switchgrass (Panicum Virgatum) To Degrade Atrazine In A Phytoremediation Setting., Ian J. Murphy, Joel R. Coats

Joel R. Coats

Atrazine is a widely used herbicide in agriculture. Non-point source contamination of groundwater and drinking water may pose a significant threat to humans, wildlife, and the environment. Phytoremediation may provide a cost-effective strategy for reducing non-point source contamination of atrazine from agricultural runoff. Previous studies have shown that the rhizosphere of the native prairie grass, switchgrass (Panicum virgatum) is capable of enhancing the degradation of atrazine in soils. Biodegradation also may occur within the plant biomass; however, the extent to which this occurs has not been studied. We hypothesize that switchgrass has the capacity to degrade atrazine in vivo, in ...


Elemol And Amyris Oil Repel The Ticks Ixodes Scapularis And Amblyomma Americanum (Acari: Ixodidae) In Laboratory Bioassays., J.F. Carroll, G. Paluch, Joel R. Coats, M. Kramer 2016 United States Department of Agriculture

Elemol And Amyris Oil Repel The Ticks Ixodes Scapularis And Amblyomma Americanum (Acari: Ixodidae) In Laboratory Bioassays., J.F. Carroll, G. Paluch, Joel R. Coats, M. Kramer

Joel R. Coats

The essential oil from Amyris balsamifera (Rutaceae) and elemol, a principal constituent of the essential oil of Osage orange, Maclura pomifera (Moraceae) were evaluated in in vitro and in vivo laboratory bioassays for repellent activity against host-seeking nymphs of the blacklegged tick,Ixodes scapularis, and the lone star tick, Amblyomma americanum. Both bioassays took advantage of the tendency of these host-seeking ticks to climb slender vertical surfaces. In one bioassay, the central portion of a vertical strip of filter paper was treated with test solution and ticks placed or allowed to crawl onto the untreated lower portion. In the other ...


Disposition Of Atrazine Metabolites Following Uptake And Degradation Of Atrazine In Switchgrass., Vurtice C. Albright III, Joel R. Coats 2016 Iowa State University

Disposition Of Atrazine Metabolites Following Uptake And Degradation Of Atrazine In Switchgrass., Vurtice C. Albright Iii, Joel R. Coats

Joel R. Coats

Extensive use of the agricultural herbicide atrazine has led to contamination of numerous ground and surface water bodies. Research has shown that it can have a variety of negative impacts on numerous non-target organisms in the environment. Phytoremediation is one strategy that has been studied to remove atrazine contamination. This paper investigates the hypothesis that switchgrass (Panicum virgatum) can exude metabolites of atrazine after uptake and degradation, which has been suggested by prior research. Pots planted with switchgrass were treated with a 4 ppm solution of atrazine spiked with [14C]atrazine. After 4 days, switchgrass plants were transplanted to new ...


Improved Corn Ethanol Fermentation And Oil Distribution By Using Polysaccharide Hydrolyzing Enzymes, Linxing Yao, Pawarisa Luangthongkam, Tong Wang, Buddhi P. Lamsal, Tao Fei, Hui Wang, Lawrence A. Johnson, Mohan Dasari 2016 Iowa State University

Improved Corn Ethanol Fermentation And Oil Distribution By Using Polysaccharide Hydrolyzing Enzymes, Linxing Yao, Pawarisa Luangthongkam, Tong Wang, Buddhi P. Lamsal, Tao Fei, Hui Wang, Lawrence A. Johnson, Mohan Dasari

Tong Wang

We determined the effects of a commercial proprietary formulation of polysaccharide hydrolyzing enzymes on ethanol fermentation performance, oil partitioning and recovery, and quality of dried distillers grains with solubles (DDGS) on a 1.5-L and 50-L fermentation scale. The enzyme was added at the start of fermentation. Whole beer was subjected to beer well incubation, distillation, and separation of thin stillage from the wet cake. The enzyme promoted faster ethanol production without affecting the final ethanol yield. The enzyme treatments resulted in 8–18% higher wet yield of thin stillage than the control, 13–21% of oil increase in thin ...


Combinatory Effect Of Changing Co2, Temperature, And Long-Term Growth Temperature On Isoprene Emissions, Michael Cole 2016 DePaul University

Combinatory Effect Of Changing Co2, Temperature, And Long-Term Growth Temperature On Isoprene Emissions, Michael Cole

DePaul Discoveries

Isoprene, the most abundant hydrocarbon in the atmosphere, plays a significant role in atmospheric chemistry. Its reactions with NOx lead to the formation of ozone in the lower troposphere, which is harmful to plants and detrimental to human health. As air temperatures and CO2 concentrations increase with climate change, it is uncertain how isoprene emissions from plants will respond. We hypothesized that isoprene emissions will increase with the combination of increasing temperature and CO­2 concentrations. We predict that oaks grown at a higher temperature will exhibit an increase in isoprene emissions with combined short-term increases in temperature ...


The Correlation Between Basal Isoprene Emissions And Climate Of The Native Range Across Oak Species, Mary J. Babiez 2016 DePaul University

The Correlation Between Basal Isoprene Emissions And Climate Of The Native Range Across Oak Species, Mary J. Babiez

DePaul Discoveries

Isoprene is a biogenic volatile organic compound that is emitted by various plant species and plays an important role in the chemistry of the atmosphere. When it reacts with pollutants in the air, such as nitrogen oxides, the precursor to ozone (O3) is formed. In this experiment, we measured leaf emissions from 20 different oak species at the Morton Arboretum (Lisle, Illinois). The aim was to better understand differences in isoprene emissions across oak species. Since emissions have been found to protect leaves against brief periods of heat stress, we hypothesized that oaks native to areas with greater variations ...


Trimethylated Lysine 4 At Histone 3 Shows The Same Circadian Rhythm At Promoters Of Diversely-Expressed Genes In Chlamydomonas Reinhardtii, Robyn M. Wilson 2016 Western Kentucky University

Trimethylated Lysine 4 At Histone 3 Shows The Same Circadian Rhythm At Promoters Of Diversely-Expressed Genes In Chlamydomonas Reinhardtii, Robyn M. Wilson

Masters Theses & Specialist Projects

Circadian clocks are biochemical mechanisms that allow eukaryotic and some prokaryotic organisms to coordinate their physiology with daily environmental changes. It enables organisms to increase their fitness by taking advantage of beneficial environmental conditions while also avoiding or restricting certain sensitive processes during harsh conditions. Similarly, post-translational histone modifications allow eukaryotic organisms to regulate gene expression in response to environmental or developmental factors. Some post-translational modifications of histones are associated with active transcription while others are associated with repressed transcription depending upon the location, type and degree of modification. Trimethylation of lysine 4 on the N-terminal tail of histone H3 ...


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