Plant Biology Commons^™

Anther Appendages Of Incarvillea Trigger A Pollen-Dispensing Mechanism, Yi Han, Can Dai, Chun-Feng Yang, Qing-Feng Wang, Timothy J. Motley

Biological Sciences Faculty Publications

Background and Aims Anther appendages play diverse roles in anther dehiscence and pollen dispersal. This study aims to explore the pollen-dispensing mechanism triggered by special anther appendages in Incarvillea arguta.

Methods Field studies were conducted to record floral characteristics, pollinator visitations, and flower-pollinator interactions. Measurements of flowers and pollinators were analysed statistically. Pollen counts following a series of floral manipulations were used to evaluate pollen dispensing efficiency and function of the anther appendages.

Key Results Field observations determined that two species of Bombus (bumble-bees) were the primary pollinators of I. arguta with a mean visiting frequency of 1.42 visitations …

Fine Root Vitality And Its Application In A Minirhizotron Study Of A Co2 Enrichment In A Florida Scrub Oak Ecosystem, Brandon Todd Herbert

Biological Sciences Theses & Dissertations

Minirhizotron images are assigned color codes to approximate the age of individual roots in situ. Triphenyl-tetrazolium chloride (TTC) has been used to measure the vitality of plant tissue by detecting dehydrogenase activity. TTC was used to assess the vitality of root tissue by color in a scrub oak ecosystem at Kennedy Space Center in central Florida. Roots were excavated, sorted into four color classes and stained with TTC. The product of the reduction of TTC by dehydrogenase enzyme, formazan, was extracted and its absorbance recorded using a spectrophotometer. A significant difference (p2 enrichment being conducted on a scrub oak …

Isoetes Toximontana (Isoetaceae), A New Quillwort With Green Megaspores From The Northern Cape Of South Africa, Lytton John Musselman, J. P. Roux

Biological Sciences Faculty Publications

Isoetes toximontana is only the second quillwort reported from the Northern Cape region in South Africa. It occurs in shallow water on the Gifberg. Megaspores are uniformly tuberculate on the proximal surface; their distal surfaces may have occasional rugi along with bullae. They are olive green when dry. Microspores are brown and aculeate. Preliminary field studies suggest that an unexpected diversity of quillworts is found in this region.

Isoetes Mattaponica (Isoetaceae), A New Diploid Quillwort From Freshwater Tidal Marshes Of Virginia, Lytton John Musselman, W. Carl Taylor, Rebecca D. Bray

Biological Sciences Faculty Publications

Isoetes mattaponica is a rare quillwort of freshwater tidal rivers of eastern Virginia with a somatic chromosome number of 2n = 22. Megaspores have low rugulate muri on both the proximal and distal surfaces; the girdle is broad. Microspores are echinate-spinose with ornamented spines. Isoetes mattaponica may be one of the parents of several polyploids in the Southeastern United States.

The Genus Striga (Scrophulariaceae) In Africa, Kamal I. Mohamed, Lytton John Musselman, Charles R. Riches

Biological Sciences Faculty Publications

Twenty-eight species and six subspecies of the hemiparasitic genus Striga Lour., witchweed, occur in Africa. Twenty-two species are endemic. Witchweeds occur throughout the continent with greatest diversity in the grasslands and savannas north of the equator. Striga gesnerioides (Willd.) Vatke and S. hermonthica (Del.) Benth. have developed host-specific strains that may have distinct morphotypes. me accord these no formal taxonomic status. Striga hermonthica and S. asiatica (L.) Kuntze, limited to agroecosystems, may be recently derived from non-ruderal species. Striga hirsuta Benth. and S. lutea Lour., sometimes treated as conspecific with S. asiatica, are recognized as distinct species restricted …

Studies On The Biology Of Striga Aspera (Scrophulariaceae) In Nigeria, Emmanuel Izaka Aigbokhan

Biological Sciences Theses & Dissertations

Studies on Striga aspera are few and little information exists on its relationship with the morphologically similar and much studied S. hermonthica. Both species are sympatric in West Africa and if they hybridize, may serve as virulent gene reservoirs for each other.

The primary focus of this study was on the biology of S. aspera in Nigeria. The research focussed on its distribution, phenology, cytology, hybridization, seed dormancy, viability and germination in relation to S. hermonthica. Related studies involving the hybrids include genetic and morphological variability, pathogenicity and the simultaneous dual infection of a maize plant by both species.

In …

Toxin Producing Phytoplankton In Chesapeake Bay, Harold G. Marshall

Biological Sciences Faculty Publications

Three diatoms and nine dinoflagellates, known to be associated with toxin production, have been identified within Chesapeake Bay. Over the past several decades this number has increased to its present level so that they now represent approximately 1.7% the total number of phytoplankton species reported for the Bay.

Fine Root Biomass Distribution And Production Along A Barrier Island Chronosequence, Mark Jeffrey Stevenson

Biological Sciences Theses & Dissertations

Fine roots play an important role in community development on barrier islands. Fine roots can influence nutrient losses from the soil environment along with regulating water loss based on their distribution and concentration (Nobel et al., 1989; Gleeson and Tilman, 1990). A sequential coring method was used to determine fine root biomass and total biomass along a chronosequence of barrier island dunes and swales on the Virginia Coast Reserve - Long Term Ecological Research Site. Fine root production and the effects of nitrogen fertilization were also examined using an ingrowth core method along the chronosequence. Live fine root biomass, total …

The Effect Of Nitrogen Fertilization On The Phenology Of Roots In A Barrier Island Sand Dune Community, Everett P. Weber

Biological Sciences Theses & Dissertations

Little work has been done on the phenology of root growth and senescence largely due to methodological difficulties. The application of minirhizotron technology has enabled the tracking of individual roots through an entire growing season. As a result, direct measures of turnover, root growth, and an analysis of cohorts were made. Small plots on a 36 year old dune on Hog Island, a barrier island in the Virginia Coast Reserve Long Term Ecological Research Site, were fertilized with nitrogen. Minirhizotron tubes were installed in each fertilized and control plot. Each tube was sampled monthly for nine months, March through October …

Seasonal Relationships Between Phytoplankton Composition, Abundance, And Primary Productivity In Three Tidal Rivers Of The Lower Chesapeake Bay, Harold G. Marshall, Kneeland K. Nesius

Biological Sciences Faculty Publications

The seasonal abundance and successional patterns of phytoplankton, including autotrophic picoplankton, are compared to spring, summer, and fall primary production maxima that occurred in three tidal rivers. The tidal freshwaters were dominated by diatoms, chlorophytes, and cyanobacteria during a late spring through early fall period of maximum growth. In contrast, downstream assemblages were dominated by estuarine diatoms, dinoflagellates, and cryptomonads which developed spring pulses and a protracted summer-fall maximum. Autotrophic picoplankton produced a major summer pulse at all river stations with reduced abundance during other seasons. The mean annual productivity rates for the tidal James, Rappahannock, and York rivers were …

The Pollen Exostructure Of Striga (Scrophulariaceae), Mark A. Deleonardis

Biological Sciences Theses & Dissertations

In this survey, the pollen exostructure of 13 Striga species was examined using light microscopy and scanning electron microscopy. Two of the 13 species were also observed by transmission electron microscopy to assess major differences in exine composition. Striga pollen is consistently spherical to oblate, isopolar, tectate, and three or four colpate. Sculpturing may be psilate, psilate-perforate, finely rugulate, or coarsely rugulate. The equatorial width of the species surveyed ranged from 15 to 30 micrometers. It is concluded that variation in Striga pollen sculpturing, aperture structure, and size support the current taxonomy of the genus.

The Effect Of Pre-Sterile Medium Ph Photoperiod And N6-(2-Isopentenyl)-Adenine (2ip) On Shoot Production During Stage Ii Micropropagation Of Rhododendrons, Lori Longo Smith

Biological Sciences Theses & Dissertations

The number of shoots produced during a six week subculture of two Rhododendron sp., cultivars Rocket and Gibraltar was the same for both 16 and 24 hour photoperiods under cool white fluorescent lights, whereas significantly fewer shoots were produced under a 10 hour photoperiod for ‘Rocket.' Increasing concentrations of N₆- (2-isopentenyl)- adenine (2iP) from 0 to 32 μMin Anderson's medium resulted in proportional increases in shoot number. When shoots were cultured in the presence of indole-3-acetic acid (IAA) and 2iP, shoot multiplication was increased significantly over shoots cultured with 2iF alone. No interaction affecting shoot multiplication was …

Organic Matter Budgets And Models For Four Plant Communities In The Great Dismal Swamp, J. Patrick Megonigal

Biological Sciences Theses & Dissertations

Budgets and models of organic matter dynamics were developed for one mesic and three seasonally flooded plant communities in the Dismal Swamp. Components included aboveground parts, belowground parts, litter and soil organic matter (SOM).

Net primary- production was significantly greater on them flooded sites. Comparisons show that the Dismal Swamp is highly productive despite relatively low nutrient inputs.

Budget calculations showed that over 65% of the total input to SOM comes from roots. Leaves contributed about 70% of the aboveground inputs.

The model predicted that species composition, aboveground biomass and turnover rates on the cedar site will become quite similar …

Morphological Variation Of The Foraminifer Elphidium Excavatum (Terquem) On Crumps Bank And Willoughby Bank, Chesapeake Bay, Virginia, Pamela Kay Painter

OES Theses and Dissertations

Six variants of the highly variable foraminiferal species, Elphidium excavatum (Terquem) were recognized in the Crumps Bank and Willoughby Bank areas of the southern Chesapeake Bay. Measurements of the size of the test, the number of chambers, the number of umbilical bosses, and the number and average length of the sutural bridges on the last formed chamber, and opaqueness or translucence of the test were made on 30 specimens from each of 36 stations selected for differences in environmental parameters. The measurements were statistically analyzed by discriminant analysis to test the hypothesis that the variants are distinct morphotypes and to …

Variation In Leaf Macronutrients Of Overstory Trees As Influenced By Species Season And Soil Type In The Great Dismal Swamp Of Virginia, Bruce J. Bandle

Biological Sciences Theses & Dissertations

Leaf macronutrient variation was studied in four plant communities in the Dismal Swamp of Virginia. composition differed markedly between these sites. Soils and species Eight important overstory trees were studied in August 1980; whereas red maple (Acer rubrum L.} and black gum (Nyssa sylvatica Marsh.}, which occurred on all four sites, were sampled seasonally. Significant differences (p .05) were found in the nutrient concentrations of the leaves between species, seasons, and sites. These differences may be attributed to inherent species characteristics, leaf expansion, nutrient translocation, and differences in soil organic matter content, pH, and degree of …

Plant Distribution And Succession Within Interdunal Depressions On A Virginia Barrier Dune System, Robert Wayne Tyndall

Biological Sciences Theses & Dissertations

A unique series of interdunal depressions was recognized on the barrier dune system of southeastern Virginia. Plant distribution and succession, and environmental factors controlling them, were studied in the series. Plant community distribution appears to be predominantly controlled by soil moisture, interspecific competition, and feral hog disturbance. Both biotic and physiographic succession are apparent with Quercus virginiana probably climax for both. Salt spray and feral hog and migratory waterfowl activity are important controlling factors of plant succession. Results indicate that the zonal appearance of shrubs and trees on the Virginia and North Carolina coasts is due to the absence of …

An Investigation Of The Nucleotide Cyclic 3'5' Adenosine Monophosphate In Young Hypocotyls Of Pisum Sativum L., Gary Marsh Hilton

Biological Sciences Theses & Dissertations

Concentrations of cAMP increased with time in pea hypocotyls assayed at 24 hour intervals over a period of four days. The highest concentration was 20.1 pmoles/mg protein which occurred in 96 hour hypocotyl tips. Ninety-six hour root bodies (dissected region between tip and embryo) achieved a concentration of 8.6 pmoles/mg. Concentrations of cAMP in embryos remained constant around one pmole/mg for three days and values doubled on the fourth day.

Hypocotyls, after germination for 72 hours, were dissected and incubated for various lengths of time in water and 3xl0^-8M IAA. Tips incubated for two hours showed a tenfold …

Structural Comparisons Of Four Plant Communities In The Great Dismal Swamp, Claire Virginia Dabel

Biological Sciences Theses & Dissertations

Four plant communities in the Great Dismal Swamp, located on the coastal plain in southeastern Virginia, were sampled and estimates of density, basal area and aboveground standing crop biomass were determined, Biomass was estimated as 229,800 kg/ha in the Chamaecyparis thyoides community and as 344,500 kg/ha in the Taxodium distichum community. Biomass for the two hardwood communities, the

Acer-Nyssa community and mixed hardwood (Quercus-Nyssa-Acer-Liriodendron-Liquidamber) community was estimated as 195,700 kg/ha and 194,600 kg/ha respectively and did not differ significantly (P

Measurement Of Transpiration In Pinus Teada L. And Liquidambar Styraciflua L. In A Closed Environment Growth Chamber Using Tritiated Water, Jean K. Czoch

Biological Sciences Theses & Dissertations

Transpiration rates of loblolly pine (Pinus taeda L.) and sweetgum (Liguidambar styraciflua L.) were measured at two different water vapor pressure deficits (V.P.D.) in a controlled environment growth chamber using tritiated water as a tracer. The trees were maintained in a sealed plant bed containing a hydroponic nutrient solution. Samples of leaves, chamber air, spiked nutrient and control solutions were assayed for activity using liquid scintillation techniques. The transpiration rate of sweetgum (4.95 ml/hr/gm) was found to be 5 times greater than that of loblolly pine (1.03 ml/hr/gm) at the lower V.P.D. and 8 times greater at …

Plant Succession In The Great Dismal Swamp Of Virginia, Susan Woodward Walker

Biological Sciences Theses & Dissertations

Vegetational composition and environmental parameters were analyzed. for 14 stands. Cluster diagrams based on index of similarity values illustrated interstand relationships. The Index of Fluctuation was developed for the analysis of intrastand dynamics. Based on the densities and numbers of species of trees and saplings within a stand, it indicated degree of compositional stability. It was concluded that present vegetation is divided into relatively distinct communities which have resulted, at least in part, from disturbance.