Plant Science & Landscape Architecture Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/2797

Browse

Now showing 1 - 20 of 253

Nematodes associated with roses and the root injury caused by Meloidogyne hapla Chitwood 1949, Xiphinema diversicaudatum (Micoletzky 1927) Thorne 1939, and Helicotylenchus nannus Steiner 1945
(1959) Davis, Ronald Allan; Jenkins, W. R.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
Few papers have been published concerning the cytological and histological effects of plant parasitic nematodes on their hosts. Most of this type of work has been done on the root-knot disease. Christie (2) described the development of root-knot nematode incited galls on tomato seedlings, reporting that these nematodes caused hypertrophy of cortical, pericyclic, and endodermal cells, hyperplasia of the pericycle, formation of xylem elements from parenchyma surrounding giant cells, and retardation of meristematic activity in the root tip. He also reported on the development and morphology of giant cells (large, multinucleate cells resulting from a stimulatory effect of nematode feeding). Krusberg and Neilsen (8) observed similar cytological responses in their work with Meloidogyne incognita acrita Chitwood 1949 infections of Porto Rico variety of sweet potato. Other investigators worked primariJy on the cytology and morphology of giant cells and giant cell nuclei. According to Tischler (from Christie, 2), division of giant cell nuclei was by normal mitosis in early stages of giant cell development, but later divisions occurred by amitosis and by fragmentation. However, Nemec (from Christie, 2) felt that divisions by amitosis and .fragmentation as reported by Tischler were actually stages of nuclear coalescence. Linford (9) described the method by which root-knot nematodes feed on giant cells and noted that substances were extruded from the stylet during feeding. Kostoff and Kendall (7), working with galled roots of Nicotiana hybrids, reported that secretions by the nematode increased cell wall permeability causing exosmosis and resulting in an accumulation of food in the region of invasion. Consequently, growth of plant tissues in these regions was accelerated and was expressed morphologically as swellings or galls on the roots. In 1942, Alstatt (1) tested the susceptibility of several strains and varieties of rose stocks, including Rosa multiflora Thunb. to a root-knot nematode. Of 13 different understocks, only one was found resistant. Lyle (10) and Massey (12) indicate that root-knot nematodes cause a serious disease of rose. Reynolds (15) found that in Meloidogyne incognita (Kofoid and White 1919) Chitwood 1949 infections of R. multiflora seedlings, the nematode entered the root and stimulated giant cell development; but galls occurred only rarely and were sometimes found on the end of long roots as a result of the penetration of many larvae. Martin (11) reported M. hapla as producing small, hard, galls on rose roots in Rhodesia and Nyasaland. M. hapla was reported by Van Der Linde (22) to infest a rose thornless understock. Two genera of ectoparasitic nematodes have been associated with root gall formation. Van Gundy (23) reported that galls induced on rough lemon roots by Hemicycliophora arenaria Raski 1958 were due to a hyperplastic response of the cortical tissue. Schindler (18) demonstrated that galling of rose roots was caused by Xiphinema diversicaudatum (Micoletzky 1927) Thorne 1939, but he did not investigate their cytological effects. In a survey of greenhouse roses, Schindler (17) found Xiphinema and Pratylenchus to be the most widely distributed genera and to occur more frequently than any other nematodes. Other genera found were: Criconemoides, Paratylenchus, Helicotylenchus, Hemicycliophora, Belonolainius, Trichodorus, T,ylenchus, Aphelenchoides, Psilenchus, and Meloidogyne. Sher (21) described the pathogenicity of Pratylenchus vulnus Allen and Jensen 1951 on rose, reporting that rose plants infested with this species were stunted and chlorotic and the root systems were necrotic with few feeder roots. Other nematodes which have been found associated with rose are Pratylenchus pratensis (de Man 1880) Filipjev 1936 (3,14), P. penetrans (14) Sher and Allen 1953 P. scribneri Steiner 1943 (13), and Ditylenchus dipsaci (Kuhn 1857) Filipjev 1936 (5). This present study was initiated to determine the occurrence and distribution of nematodes associated with roses grown outdoors. In addition the cytological and histological effects of Meloidogyne hapla Chitwood 1949, by Xiphinema diversicaudatum (Micoletzky 1927) Thorne 1939, and Helicotylenchus nannus Steiner 1945 on rose roots was determined.
GROWTH REGULATORS AND THE FLOWERING OF EVERGREEN AZALEAS (RHODODENDRON CV.)
(1960) Ballantyne, David J.; Link, Conrad B.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
Spraying experiments were conducted in 1958 and 1959 to find the effectiveness of certain growth regulators upon multiple flower bud formation and rate of flower bud development of evergreen azaleas. Paper chromatograms of extracts of vegetative buds and of flower buds treated with 37°F. storage and potassium gibberellate (GAk) sprays, were tested with a wheat coleoptile bioassay in 1959. Foliar sprays of 2, 3, 5-triiodobenzoic acid (TIBA), an antiauxin, showed evidence of inhibiting multiple flower bud formation, and a foliar spray of 2,200 ppm indoleacetic acid (IAA) tended to promote multiple flower bud formation. The time of spraying in relation to the time of floral initiation apparently is important if growth regulators are to influence multiple flower bud formation. The rate of flower bud development was increased by two weeks of 37°F. storage and either two sprays of 200 ppm TIBA or single sprays of 160, 400 or 1,000 ppm TIBA, or by three weeks of 45°F. storage and a single spray of 1,000 ppm IAA. Rate of flower bud development was increased by two sprays of 200 ppm TIBA and one spray of 1,000 ppm gibberellic acid (GA). Flower bud dormancy was removed by foliar sprays of 900 ppm GAk with no cold storage or two weeks of 37°F. Four weeks of 37°F. storage was effective without GAk and six weeks of 37°F. storage gave no increase over four weeks of storage. Concentrations of GAk lower than 900 ppm were ineffective. GAk was effective whether applied before or after two weeks of 37°F. storage. Naphthalene acetic acid in concentrations of 9 ppm or greater inhibited the rate of flower bud development. Apical dominance was removed by 800 ppm or more of TIBA. The wheat coleoptile bioassay indicated that a growth inhibitor in the flower buds was removed by three or more weeks of 37°F. storage and three sprays of 1,000 ppm GAk. The promoter was not in vegetative buds and could not be considered to be IAA, GA or GAk.
A Study of Resistance to the Sweet Potato Wilt Pathogen, Fusarium oxysporum Schlecht f. batatis (Wr.) Snyder & Hansen, and of Histological Aspects of the Host-pathogen Complex
(1963) Wells, John Milton; Kantzes, James G.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
Research on Fusarium wilt of sweet potato, a vascular disease caused by Fusarium oxysporum Schlecht f. batatis (Wr.) Snyder & Hansen, was undertaken to determine the susceptibility of various sweet potato lines to Maryland isolates of the pathogen under field and greenhouse conditions. Highly resistant lines would be useful as sources of resistance to Fusarium wilt in sweet potato breeding programs. In 2 years of field and greenhouse trials, 94 different lines of sweet potato were inoculated with a composite spore and mycelial suspension of 5 Maryland isolates of F. oxysporum f. batatis. Results indicated that the following lines were highly resistant to the pathogen: the foreign plant introductions P.I. 153655 ("Tinian"), P.I. 153906, P.I. 153907, and P.I. 251602; the variety Pelican Processor; and the breeding selections B-6842 from the United States Department of Agriculture Plant Industry Station at Beltsville, Maryland, and T-7 from the Georgia Coastal Plain Agricultural Experiment Station at Tifton, Georgia. Greenhouse experiments showed that the host range of Fusarium oxysporum f. batatis should include an additional species of Morning Glory, lpomoea pandurata (L.) G. F. w. Mey. Furthermore, no symptoms of infection were obtained on various crop plants commonly grown in rotation on land used for sweet potato culture. Physiological studies in the laboratory and greenhouse indicated that no significant levels of fungitoxic substances were present in either uninoculated or inoculated ''Tinian" plants. Nor could a fungal metabolite be detected, under the existing experimental conditions, which was toxic to a susceptible variety of sweet potato (Porto Rico) but not to the resistant ''Tinian". A study was made of the basis for resistance of the foreign plant introduction "Tinian" (P. I. 153655). Histological examinations of serial stem sections of the susceptible sweet potato variety Porto Rico and of the resistant foreign plant introduction ''Tinian" were made from plants collected at 3-day intervals following inoculation with spores of the pathogen. It was found that "Tinian" responded to infection by the production of tyloses in advance of the fungus. Twelve days after inoculation, 75 - 88% of the vessels which were 22 - 32 mn above the invasion site at the base of the plant were completely filled with tyloses. This compared to only 0 - 3% in the uninoculated control plants. Furthermore, no mycelia or spores could be detected in tnis region but were present in 25 - 50% of tne vessels within 11 mm of tne invasion site. In the variety Porto Rico the occurrence of tyloses in the inoculated plants was not significantly greater than in the uninoculated controls, except near the invasion site where after 12 days 3 - 6% of the vessels contained small 1 tyloses. The pathogen was not limited, as in ''Tinian", to the immediate invasion site. Tnis suggests that tne production of tyloses in "Tinian may represent an important defense mechanism against Fusarium wilt.
The kinetics and quantum yield of photophosphorylation in Anacystis nidulans (Richt.) Drouet
(1972) Owens, Olga v. H.; Krauss, Robert W.; Plant Physiology; Digital Repository at the University of Maryland; University of Maryland (College Park, MD)
The active metabolite, ATP, serves not only as a high energy intermediate but also as a controller of some enzymatic reactions. In plant cells, the larger part of the ATP is formed by photophosphorylation. In this paper the rates, the quantum yields, and the wavelength dependencies of photophosphorylation in the blue-green alga Anacystis nidulans are reported. A fluorometric method for determination of enzymatically produced NADPH from ATP was adapted for use on cell extracts. In the light, the ATP level was 0.15 to 0.25 µmoles/mg chl. In the dark, the ATP level was 70% of that in light. In both darkness and anaerobosis, the level was 20%. A return to the light restored the ATP level from both conditions. Dark, anaerobic cells were exposed to measured irradiancies of 710 nm and 620 nm. The rate of ATP formation was measured within the first few seconds and found to be directly proportional to absorbed intensity. Saturation of the rates occurred at an intensity one-tenth the optimum for oxygen production. Quantum requirements of 6-8 were similar for each of the two wavelengths. The system II inhibitor DCMU, had a greater effect at 620 nm that at 710 nm indicating an involvement of system II in photophosphorylation only at 620 nm. At low intensities and over long time periods white light failed to produce a saturating steady-state level of ATP indicating a simultaneous consumption of ATP. Measurements in short dark periods following marginal illumination showed consumption of ATP to be 2 to 4 times greater that production in weak light. Thus, the quantum requirement can be calculated to be 2. ATP formation, therefore, is not the limit ing factor in co2 fixation. The evidence is the high quantum yield of photophosphorylation and the unsaturation of co2 fixation at intensities at which ATP synthesis is saturated.
Net Productivity of Emergent Vegetation at Horn Point Salt Marsh
(1975) Cahoon, Donald Richard; Stevenson, John C.; Botany; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
Analyses of monthly standing crop, daily rates of production, and variations in yearly productivity for 5 production for the Spartina patens/Distichlis spicata mixture were conducted over two consecutive growing seasons for a Chesapeake Bay brackish marsh. Regression models for plant height and dry weight biomass were generated for all that the relationship between height and dry weight within each species is the same for all seasons of the year except in the species Spartina alterniflora and Phragmites australis. Positive correlation coefficients ranged from .27 for S. alterniflora to .96 for P. australis with the other species having intermediate value. Overall, production at Horn Point is lower than most other values in the literature with the 2-year average for S. alterniflora (676 g/m2) being 1/2 the average for the Atlantic Coast but the 2-year average for S. patens (628 g/m2) being slightly higher than its Atlantic Coast average. On a square meter basis, the primary producers rank in the following order of importance for the two year average of standing crop: Typha angustifolia (985 g/m2), Phragmites australis (892 g/m2), S. alterniflora/Amaranthus cannabinus (676 g/m2), S. patens/D. spicata (628 g/m2), and Hibiscus moscheutos (531 g/m2). However, the most important zones in terms of areally weighted production (in metric tons) for 1973 at Horn Point Marsh are the S. patens/D. spicata (7.61), H. mocheutos (5.07), S. alterniflora/A. cannabinus (3.22), P. australis (0.659), and T. angustifolia/H. moscheutos (0.644). In the brackish marsh (S. patens/D. spicata) exclosure experiments demonstrated that almost 100% of the net primary production (NPP) passes through the detritus food chain but in the contiguous fresh marsh (H. moscheutos) 37% of the NPP is utilized by the grazing food chain. Underground production for S. patens/D. spicata was determined by an experimental approach involving transplantations of underground material and a dry weight shoot:root ratio of 1:16 was determined over a twelve month period. An efficiency rate for conversion of visible solar radiation to plant production in 1974 ranged from 0.11% for H. moscheutos in the Typha/Hibiscus zone to 1.12% for the Typha angustifolia/Hibiscus moscheutos mixture.
A Study of the Soils Derived from Serpetinite and Associated Rocks in Maryland
(1978) Rabenhorst, Martin Capell; Foss, John E.; Agronomy; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
Approximately 25,000 acres have been mapped as serpentinite-derived soils in Maryland. While fertility studies have been done in serpentine areas, little work has been undertaken concerning the genesis of these soils. The objectives of this study were: 1) characterize the properties of soils formed from serpentinite and associated mafic rocks; 2) apply the results of the characterization study to an understanding of the genesis of these soils; and 3) examine the mapping and classification of serpentine soils with reference to geologic mapping. In a reconnaissance effort, 48 sites were sampled and analyzed for extractable Mg, Ca, P, and K and for pH. From field observations and these data, seven locations were selected for profile descriptions and detailed sampling. Physical, chemical , and mineralogical analyses were conducted on these samples. All serpentine profiles showed weak to moderate expression of argillic horizons and as a result of high Mg saturation, are classified as Alfisols. Argillic horizons in the non-serpentine profiles were strongly developed. Serpentine minerals were generally abundant in the > 0.2 μm fractions of serpentinite-derived soils. These weather to form expansible 2:1 minerals in the finer fractions. Vermiculite and smectite were important in both serpentine and non-serpentine profiles. The presence of quartz, mica, and feldspar in the surface horizons of all profiles indicate that eolian additions have occurred in many counties in the Maryland Piedmont. Comparison of soil mapping with geologic mapping has revealed large acreages of serpentine soil units mapped over non-serpentine mafic rock . This demonstrates the need to better utilize available geologic information in soil mapping. Serpentinitic mineral families are not currently recognized in any soil series in Maryland. Three of the four serpentine profiles, however, contained high levels of serpentine minerals. There is, therefore, a need to recognize serpentinitic soil families in Maryland in order to better differentiate between soils formed from serpentinite or from non-serpentine mafic rocks.
A Revision of North American Melanthium L. (Liliaceae)
(1978) Bodkin, Norlyn Lee; Reveal, James L.; Botany; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
Melanthium L. (Liliaceae ) is a genus of perhaps eight species with the four species of North America distributed from central Iowa eastward to southern New York, south to northern Florida and eastern Texas. The type species , M. -virginicum L., is found over this entire range growing commonly in swamps , marshes and bogs. Melanthium latifolium Desr. , found mostly on rich wooded slopes, and M. parviflorum (Michx.) S. Wats. located at higher elevations, occur mainly in the mid-Appalachian mountains. Melanthium woodii (Robbins ex Wood) Bodkin, comb. nov., is known from rich deciduous slopes of the Ozark Plateaus where it is very local and rare, and from five small disjunct populations in three eastern states. The major decision made in this treatment is the maintenance of Melanthium as distinct from the heterogeneous genus Veratrum L. on the basis of leaf size and shape, inflorescence, features of the tepalular glands and claws, adnation of stamens to tepals and general habit of the plants. The numerous synonyms associated with the name Melanthium are treated and either included under that genus , or excluded and assign d to their proper genera. The four (tentatively) Asian species, all of southwestern China , are not discussed due to a paucity of recent material.
A REVISION OF THE GENUS ODONTONEMA (ACANTHACEAE)
(1982) Baum, Vicki M.; Reveal, James L.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
Odontonema Nees (Acanthaceae, Acanthoideae, Acanthatae, Odontonemeae) is a New World tropical or subtropical genus of 26 species and two varieties. Members of the genus are distributed from coastal central Mexico southward throughout Latin America into northern South America, with one species located on the southeastern coast of Brasil (a second species from Brasil is from an unknown location). Odontonema also is found on the Caribbean Islands. The genus consists of four major groups which, at this time, are not given formal taxonomic recognition: 1) red-purple (rarely white) flowered species (O. callistachyum and its relatives); 2) red flowered species with typically a bottle-shaped corolla (O. schornburgkianum and its relatives); 3) white-purple flowered species with a more strongly bilabiate corolla (O. nitidum and its relatives); and 4) yellow flowered species (O. hondurense and its relatives). Although a few members of Odontonema may be seen in cultivation, the present revision is based on an examination of herbarium material found in both New and Old World herbaria, a numerical analysis of macromorphological features, and an examination of pollen morphology. The four groups within Odontonema defined above were established after the numerical analysis, and all species save one (O. cuspidaturn) were found to have 3-colporate pollen characteristic of sect. Odontonemeae. Descriptions were prepared of each species based on available herbarium specimens...
The State of Water and Cell Morphology In Deep Frozen Populus
(1985) Hirsh, Allen Gene; Solomos, Theophanes; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
By using differential scanning calorimetry, electron microscopy, light microscopy, and freezing survival experiments, it is shown that superhardy Populus balsamifera v. Virginiana (Sarg.) is capable of withstanding liquid nitrogen (LN 2) temperatures because of the formation during cooling, at a temperature of about -30°C and cooling rates less than 30°C/hr, of aqueous glasses in the intracellular solutions. In more detail, the major findings concerning the state of intracellular water are: (1) the bulk of the intracellular contents go through an equilibrium glass transition at about -28°C during slow (<5°C/hr) cooling; (2) smaller additional amounts of intracellular material go through equilibrium glass transitions at about -47°C and -70°C; (3) as a result of the resistance to homogeneous nucleation of these glass forming intracellular solutions when they are in equilibrium with extracellular ice at<.-20°c, cooling/warming at any combination of rates from 3°C/hr to 1200°C/min between -20°c and -196°C is non-injurious to fully hardened wood; (4) death associated with quench cooling in LN2 from -15°C is correlated with the devitrification, (cold crystallization) near -90°C upon warming of the very low temperature glass forming component, followed by further devitrification of the higher temperature components, especially between -30°c and -20°c; and (5) the vacuolar compartment appears least resistant to devitrification and capable of thereby causing death even when the cytoplasm resists devitrification. In addition, it was found that when fully superhardy wood is cooled slowly (3°C/hr) after being imbibed with water (doubling total water content) massive intracellular freezing occurs. Despite the fact that total tissue water of tender Populus (summer wood) is 2x that of the artifically water loaded hardy wood on a gram H20/gram dry weight basis, tender wood cooled at 3°C/hr to -50°c does not display intracellular freezing. It is killed by -2°C. It is shown that in both tender and hardy wood <10% of water is extracellular. Thus a significant excess of extracellular water appears to cause intracellular freezing and this may be a major reason for the large water loss seen in the fall 'hardening off' of most temperature zone woody plants. It is also shown that during slow cooling, the plasma membranes of both hardy and tender Populus cells stick to and collapse the cell wall, but that these membranes stay smooth in the case of superhardy cells and wrinkle markedly in the case of tender cells. Membrane-associated particles appeared to clump in the membranes of slowly cooled tender cells but not in the slowly cooled hardy cells.
Insect-Nematode-Red Pine Association in Western Maryland with Major Emphasis on Bursaphelenchus xylophilus and Monochamus spp.
(1985) Harman, Amy Susan Litten; Krusberg, Lorin R.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
Western Maryland red pines, Pinus resinosa Ait. Were examined over three years, 1982-1984, to determine the distribution of Bursaphelenchus xylophilus, the pinewood nematode. Ca. 47-year-old (older) and ca. 25-year-old (younger) trees were subdivided into the following categories: (1) trees with mostly green needles; (2) trees with mostly reddish-brown needles; (3) trees with no needles but with bark intact; (4) trees with no bark; and (5) trees with chlorotic, bleached-green needles. The pinewood. nematode infected 76.5% of older red pines and 68% of younger red pines. The nematode was not evenly distributed in trees in any tree decadence category or by tree age. Bursaphelenchus xylophilus infected 15.1% of the samples from trunk, primary and secondary branches in older red pines and 18.5% in younger red pines. By tree decadence category older trees had the highest infection (25.2%) in green needled trees (category 1) whereas younger trees had the highest infection (28.7%) in bleached-green needled trees (category 5). Trees collected in late May-early June 1982 lacked Monochamus rearings and belonged to categories 1, 2, 3 and 4. Trees from these categories had emergences of Ips spp., Tetropium schwarzianum Casey, Pissodes approximatus Hopkins and Otiorhynchus spp. in summer 1982. From bleached-green needled red pines (category 5) collected in late July-early August 1983 two Monochamus species emerged in 1984, M. carolinensis (Olivier) and M. scutellatus (Say), as well as other insects including Neacanthocinus pusillus (Kirby) and Amniscus collaris Haldemann. Chrysobothris scabripennis Cast. and Gory emerged from trees cut in 1983, but which remained uncaged in the field until 1984. Bursaphelenchus xylophilus was present in 94% of tracheal systems of both M. scutellatus and M. carolinensis. Pinewood nematode was found infesting 4.2% of N. pusillus specimens. One specimen each off. approximatus, Ips spp. and C. scabripennis were positive for B. xylophilus. Dolichomitus tuberculatue tuberculatus (Geoff.), an ichneumonid parasite, was reared from Monochamus spp. larvae. Two deutonymph mites, Dendrolaelap isodentatus (Hurlbutt) and Trichouropoda hirsuta Hirschmann, were located externally on Monochamus spp. beetles.
Morphology, Mineralogy, and Hydrology of Soils in the Triassic Culpeper Basin of Maryland
(1992) Elless, Mark Peter; Rabenhorst, Martin C.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
Soils derived from red parent materials are problematic in terms of morphologically assessing their hydrology because these parent materials are known to retard the development of redoximorphic features within their sola. This retardation phenomena may lead to misinterpretations of these soils for both agricultural and engineering purposes. Such soils occur within the Triassic Culpeper Basin of Maryland. Eleven pedons along two topohydrosequences within this basin were therefore investigated to determine the interrelationships between the soil morphology, mineralogy, and hydrology, particularly as these pertain to the development of redoximorphic features in these soils. These soils are derived from dusky red (SYR 4/4) parent materials which retard the development of redoximorphic features. Morphological descriptions of each pedon were made and the water table was monitored in both open boreholes and slotted PVC pipes at staggered depths. Bulk samples of each horizon were collected for mineralogical and chemical analyses. Results indicate that hematite is the only iron oxide in the underlying red shales and sandstones of this basin. The hematite in the soils is then inherited during pedogenesis and is responsible for the red hues exhibited throughout the profiles of the better-drained pedons and in the lower sola of the more poorly-drained pedons. Results of parent material uniformity indicate the presence of either loess, colluvium, alluvium, or mixtures of these materials with residuum within the upper sola of these same pedons. Residual, or principally residually-derived, soils remain predominantly red throughout their profile, independent of hydrology. Soils formed from non-uniform parent materials exhibit yellower hues, particularly within their upper sola. Thus, the pedogenic yellowing of these pedons may be due to either the incorporation of more easily altered foreign material than that derived from weathering of the red residual parent materials or to the presence of a seasonally-high water table in the upper sola of these pedons. Even though redoximorphic features are created through redox processes, the nature of the parent materials appears to mediate their degree of development. This study suggests that the degree of parent material uniformity be assessed prior to any judgment on the drainage classes of similar soils.
Establishing Native Grasses Along Maryland Roadways
(2000) Adamson, Nancy Lee; Turner, Thomas R.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
The use of native grasses and other meadow species in roadside rights-of-way is perceived as environmentally and economically beneficial. There is a need for more information about successful establishment procedures appropriate for the mid-Atlantic region. This study examined the use of companion species and weed control treatments for native grass establishment in three distinct regions of Maryland. A mixture of eight perennial native grasses planted included big bluestem (Andropogon gerordii Vitman), bluejoint (Colomogrostis conodensis (Michx.) Beauv.), broomsedge (Andropogon virginicus L.), deertongue (Dichonthelium clondestinum (L.) Gould), eastern gamagrass (Tripsocum doctyloides (L.) L.), indian grass (Sorghostrum nutons (L.) Nash), little bluestem (Schizochyrium scoporium (Michx.) Nash), and switchgrass (Ponicum virgotum L.). A variety of annual and perennial non-native and native grasses and two legumes planted as companion species, as well as various weed control treatments (mowing and the herbicides imazapic ((±)-2-[4,5-dihydro-4-methyl-4-( I -methylethyl)-5-oxo- I H-imidazol-2-yl]-5-methyl-3 pyridinecarboxylic acid) and triclopyr ([(3,5,6-trichloro-2-pyridinyl)Oxy] acetic acid) with 2,4-D (2,4- dichlorophenoxyacetic acid) were tested for their utility in aiding establishment of the native mixture. Companion and weed control treatments had variable effects, depending on individual species, site and climatic conditions.
The Origin and Pedogenic History of Quaternary Silts on the Delmarva Peninsula in Maryland
(2003-11-18) Wah, John Stuart; Rabenhorst, Martin C; Plant Science and Landscape Architecture (PSLA)
Soils formed in Quaternary age silts are widespread on the Delmarva Peninsula in Maryland. The origin, mode of transportation and deposition, and age of the sediments in which these soils formed have long been debated and are important to understanding climate change and to investigations of the prehistory of the Delmarva. This study was undertaken in an effort to resolve the issue of the origin of parent sediments, to examine the pedogenic history of the soils, and to gain insight into the paleoclimate of the region. Thirty nine profiles were described and sampled in two north-south transects on the upland and the broad terrace along the Chesapeake Bay on Maryland's Eastern Shore. Laboratory analyses included determination of particle size distribution, determination of Zr, Ti, Ca, and K contents of coarse silts, mineralogical analysis, and the examination of biogenic opal. The silty mantle overlying sands ranged in thickness from 150 cm to less than 50 cm, with considerable variation across the study area. Textures of this mantle were silt loam and silty clay loam with 53 to 94 percent clay-free silt and a mean clay-free particle size of 41 mm. The Zr content of the silts was uniform within profiles and across the study area while that of Ti, Ca, and K varied. Mineralogy of the silts was homogeneous across the study area. There were no features diagnostic of either fluvial/estuarine or eolian processes in the silt deposit. Minimal coarse fragments and no stratification were observed. Low chroma matrix colors of soils reflected modern drainage conditions rather than a reducing depositional environment. Pedological development argued for relatively young soils (< 30,000 years) and archaeological materials from surface horizons buried by the silts dated the onset of deposition to the end of the Pleistocene (approximately 10,500 14C years BP). The youthfulness of the silts precluded them from having been deposited during the Sangamon transgression, which occurred no more recently than 82,000 years BP, and proved unequivocally that the silts are loess. Buried paleosols were indicative of the landscape stability prior to loess deposition while phytoliths reflected a climate shift.
CHARACTERIZATION OF GLOMALIN, A GLYCOPROTEIN PRODUCED BY ARBUSCULAR MYCORRHIZAL FUNGI
(2003-12-10) Nichols, Kristine Ann; Angle, Jay S; Plant Science and Landscape Architecture (PSLA)
Glomalin is an insoluble glycoprotein produced by hyphae of arbuscular mycorrhizal (AM) fungi. It is resistant to degradation and is found in large amounts in soil. Classical operationally defined extracts of soil organic matter include a large proteinaceous fraction. Therefore, clarification of glomalin as a separate fraction of extractable soil organic matter (SOM) is needed. Proof that glomalin accumulates over long periods of time has not been attempted. The overall hypothesis tested for this dissertation is that AM fungi are the source of an abundant, unique and important SOM component. The quantity of glomalin in soils was compared with particulate organic matter (POM), glomalin, humic acid (HA), and fulvic acid (FA) which were sequentially extracted from 5 8 undisturbed U.S. soils, aggregates and agriculturally managed soils that differed in tillage, crop rotation, and/or fertilizer amendment. Each fraction was extracted with the appropriate procedure: glomalin in pH 8.0 citrate at 121C, POM by floatation in NaCl solution, and HA and FA in NaOH with acidic separation. Organic matter fractions were evaluated for total and immunoreactive protein and/or gravimetric and C weights. Percentages of C, N and H were used to characterize each fraction. Glomalin structure was examined by proton nuclear magnetic resonance (1H NMR), removal of iron and separation of amino acid and carbohydrate groups. Glomalin accumulation in pot cultures was assessed at 14-week intervals in a 294-day experiment. Glomalin was unique in protein, C, H, and N contents compared with HA, FA and POM. Glomalin contributed ca. 20% of soil organic carbon. A recalcitrant glomalin pool was discovered that might have a functional role in water-stability of aggregates. 1H NMR spectra of glomalin were unique compared with HA spectra. Extracted glomalin had tightly bound iron, organic matter, amino acids and carbohydrates. Sustainable agricultural management practices reduced tillage, increased crop diversity, and reduced synthetic amendments increased aggregate stability of bulk soil and glomalin and POM concentrations. Glomalin production under controlled conditions was affected by irradiance. These results provide evidence that glomalin is a separate and unique fraction of SOM and is important in terrestrial carbon sequestration and sustainable agricultural practices.
Management of White Rust (Caused by Albugo Occidentalis) Of Spinach and Its Impact on the NonTarget Invertebrate Community
(2003-12-16) Diagne, Mbisin; Everts, Kathryne L; Dively, Galen P; Grybauskas, Arvydas P; Plant Science and Landscape Architecture (PSLA)
White rust, caused by the oomycete Albugo occidentalis, is a major foliar disease of spinach (Spinacia oleracea). Favorable environmental conditions are required for its initiation and development. A modified version of a weather-based spray advisory program was evaluated using chemicals with different modes of action. Entomopathogenic fungi may infect Myzus persicae, a major pest of spinach. The nontarget effects of chemicals used in the management of white rust on entomopathogenic fungi and on the invertebrate community were also investigated. Both acibenzolar-S-methyl initiated at the second true leaf stage and pyraclostrobin applied according to the advisory program and weekly, reduced disease incidence compared to untreated plots. Naiad sprayed weekly reduced the percentage of aphid infested leaves, however no entomopathogenic fungi were isolated. All three chemicals caused population increases in predatory mites and phytophageous thrips. Actigard and Naiad caused increases in oribatid mites and beetle larvae populations
WATER AND NUTRIENT DYNAMICS IN CONTAINER-NURSERY PRODUCTION SYSTEMS
(2004-04-30) Ristvey, Andrew George; Lea-Cox, John D; Plant Science and Landscape Architecture (PSLA)
Water quality remains a predominant issue within the Chesapeake Bay watershed, and nutrient loading continues to undermine the progressive recovery of this ecosystem. Until recently, the ornamental plant industry has had little information to develop better management practices to increase the efficiency of water and nutrient applications. This research used an integrated approach to examine container- production systems, to develop recommendations to increase nutrient uptake efficiency and reduce runoff. A 40-month field study examined the effects of various cultural practices on irrigation and nutrient uptake efficiencies. Under cyclic scheduling, drip irrigation applied 3 to 4.5 times less water than overhead irrigation and had significantly less runoff when plants were spaced at low densities. While drip irrigation is significantly more efficient, overhead irrigation is more practical and economically feasible for most small container-nursery stock. Time Domain Reflectometry (TDR) was examined as an alternative to cyclic scheduling and when used with overhead irrigation, water applications were half that of cyclic irrigation scheduling. . This research simultaneously documented nitrogen (N) and phosphorus (P) dynamics by examining nutrient applications, uptake and leaching over the forty months. In most cases, N and P uptake efficiency and runoff was negatively affected by overhead irrigation, particularly when soluble nutrients were applied via fertigation and at low plant densities. Nitrogen and P efficiencies ranged between 10 and 30% and were dependent upon methods of irrigation and fertilization, plant density and water use. The use of both drip and TDR-scheduled overhead irrigation reduced nutrient runoff to half that of the overhead irrigation program Intensive spring nutrient uptake studies showed that N influences the total growth of Rhododendron (azalea) and P uptake is a function of P fertilization rate and growth, influenced by N rate. Moderate N rates maintained optimal growth, while total P was only required at 1/20 of this N rate. Periodicity in nutrient uptake suggests seasonal timing of fertilizers may increase N and P uptake efficiency. Novel management strategies in the area of irrigation, fertilization, and cultural practices should be adopted by the ornamental industry to improve upon low efficiencies and reduce nutrient pollution in our watersheds.
Assessment of select isolates of Trichoderma virens as a potential biocontrol against Meloidogyne incognita
(2004-05-03) Mallozzi, Tonya Suzanne; Kratochvil, Robert J.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Three isolates of the soil-dwelling fungal organism, Trichoderma virens (Miller, Giddens and Foster) von Arx., were studied as potential biocontrols for the management of root-knot nematode (RKN) on bell pepper (Capsicum annuum L.). The study was conducted within the Moisture Replacement System (MRS), which was concurrently evaluated for its ability to serve as a culture system for Meloidogyne incognita (Kofoid and White) Chitwood and as an environment supportive of the growth and maintenance of Trichoderma isolates for biocontrol studies of this nature. Trichoderma isolates selected for study did not suppress populations of RKN on bell pepper under the conditions of this study. A review of the literature provided a multitude of complexities potentially contributing to the final results obtained. Investigation into these various complexities with the incorporation of the MRS will help to fully ascertain Trichoderma's potential as a biocontrol and perhaps reveal viable alternatives in the management of RKN.
Breeding Considerations for Improving Cadmium and Zinc Hyperaccumulation in Two Thlaspi caerulescens Populations
(2004-05-05) Synkowski, Eva Claire Creighton; McIntosh, Marla S; Plant Science and Landscape Architecture (PSLA)
Cadmium is the second most widespread soil metal contaminant in the world and it has been suggested that phytoremediation using hyperaccumulator plants could be used to effectively remove harmful levels of soil metals. This research was conducted to provide basic information necessary for developing a breeding program to improve the phytoremediation potential of Thlaspi caerulescens, a promising hyperaccumulator plant. By determining the genetic structure of the source populations and estimating the heritability of traits of interest, gain from selection was predicted. Bulk segregrant analysis of DNA polymorphisms was used to identify markers linked to cadmium hyperaccumulation. DNA markers would reduce time and expense of selecting superior genotypes. However, confounding effects from marker technology, experimental design, and sample size reduced the potential for implementing the detected markers in a breeding program. Future experiments may still detect markers for hyperaccumulation and the T. caerulescens populations studied are valuable for phytoremediation application.
Hydromorphology of Piedmont Floodplain Soils
(2004-05-07) Castenson, Karen Lynn; Rabenhorst, Martin C; Plant Science and Landscape Architecture (PSLA)
Alluvial soils situated on middle locations along Mid-Atlantic Piedmont floodplains lack characteristic redoximorphic features that allow them to meet a current field indicator of hydric soil. Although these soils appear to be located in wetlands based on their hydrologic, vegetative, and electrochemical status; there is no hydric soil indicator that accurately includes soils on these landscapes. Two research sites in Maryland and one in Delaware were instrumented along a hydrosequence. Depth to water table, redox potential, and soil temperature were measured. Redox potential measurements of the hydric and possible hydric soil conclude that Fe(III) is predicted to be reduced to Fe(II) for a significant period of time during the growing season. Based on data collected over three years, the possible hydric soil was confirmed hydric. An alternate hydric soil indicator has been proposed for these landscapes.
Soil Properties and Native Plant Communities in a Kansas Prairie
(2004-08-18) Gordon, Carol Sue; Weil, Ray R.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
I hypothesized that the relative proportion of grasses and legumes in native prairie communities are associated with physical and chemical soil properties. In a greenhouse study, I determined species responses to differences in soils ex situ by individually growing three grasses, two legumes, and two composites in soils from four sites on a never-plowed prairie at The Land Institute in Saline County, KS. The highest organic matter (OM) soil produced the highest plant dry matter for five of the species. In a field study, I measured 20 soil properties in 24 quadrats (0.5 m2) with high, low, or no legume cover on the same four sites. After incubation, NH4 in subsurface soils was lower for high legume cover suggesting higher nitrification. Discriminant multivariate analysis showed the ratio, active C as a percent of total C, and percent OM were the most closely associated surface soil variables with percent legume cover.