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Articles 1 - 30 of 63
Full-Text Articles in Life Sciences
Nitrogen Fixation In Roots Of Ceanothus, W. John Hayden
Nitrogen Fixation In Roots Of Ceanothus, W. John Hayden
Biology Faculty Publications
Roots are usually out of sight and, therefore, out of mind. But as any good gardener will tell you, it is of utmost importance to understand those unique plant organs, even if their essential functions occur hidden from cursory observation. The red roots of the 2019 VNPS Wildflower of the Year, Ceanothus americanus, are particularly important because they host symbiotic bacteria that perform the essential function of nitrogen fixation. These prominent, knobby, distinctively pigmented roots are also the inspiration for the common name Redroot, applied to many species in the genus.
Endless Symbioses Most Intricate, W. John Hayden
Endless Symbioses Most Intricate, W. John Hayden
Biology Faculty Publications
Orchids, such as our Wildflower of the Year for 2016, Downy Rattlesnake Plantain (Goodyera pubescens) (Fig. 1), exemplify the interconnectedness of life on Earth. As would be the case for many kinds of plants, pollination comes readily to mind as a prominent example of mutualistic symbiosis. Downy Rattlesnake Plantain is pollinated by bumblebees and other native bees. The bees gain nectar and the orchid gets an efficient means to move pollen from one flower to another; each organism gains benefit from the interaction, the very definition of mutualism. Pollination by bees is widespread among the orchids, but there …
Seed Dispersal: A Tale Of Two Species, W. John Hayden
Seed Dispersal: A Tale Of Two Species, W. John Hayden
Biology Faculty Publications
Orchids have minute, dustlike seeds. In this respect, Goodyera pubescens (Downy Rattlesnake Plantain), the 2016 VNPS Wildflower of the Year, is a typical orchid. Like all other orchids, Goodyera seeds contain little more than a few embryonic cells enclosed in a thin seed coat. There are two advantages to small seed size in orchids: minute seeds can be produced in prodigious quantities, and they can disperse over great distances by wind.
2016 Virginia Wildflower Of The Year: Downy Rattlesnake Plantain, Goodyera Pubescens, W. John Hayden
2016 Virginia Wildflower Of The Year: Downy Rattlesnake Plantain, Goodyera Pubescens, W. John Hayden
Biology Faculty Publications
Regardless of season, Downy Rattlesnake Plantain is a delight to encounter in the woods of Virginia. This evergreen orchid is a perennial rhizomatous herb of the forest floor. The horizontal rhizomes, usually covered lightly by leaf litter, bear roots at intervals and terminate in a rosette of leaves. Leaves are alternate, somewhat crowded together, and only slightly elevated above ground level. Leaf blades are ovate, 3–8 cm long, and 1.5–3 cm wide, often of varying size within a rosette. Leaves are present year-round, bluish-green, with prominent white veins; on each leaf, a broad midvein is flanked by two smaller veins …
There's Much Left To Learn: Clethra's Chromosomes, W. John Hayden
There's Much Left To Learn: Clethra's Chromosomes, W. John Hayden
Biology Faculty Publications
Many would argue that chromosomes, genes, and DNA form the ineluctable essence of modern biology. Not only do these fundamental components of living cells provide moment-to-moment instructions by which cells carry out basic life processes, they also control inheritance of characteristics from one generation to the next. These essential functions of DNA stem from its repetitive structure. Hugely long DNA molecules are built from just four components, referenced by their singleletter abbreviations, A, C, G, and T. It is the specific sequence of these As, Cs, Gs, and Ts that constitutes the coded information of DNA. Moreover, molecular biologists have …
When It Comes To Clethra: Roots Matter, W. John Hayden
When It Comes To Clethra: Roots Matter, W. John Hayden
Biology Faculty Publications
Roots, too often, are out of sight and out of mind, but they are critical for vigorous, healthy plant growth. All plant enthusiasts—including gardeners, farmers, foresters, and naturalists—should think about and appreciate roots if they wish to acquire a holistic understanding of plant biology. This article introduces readers to the mycorrhizal roots of the 2015 VNPS Wildflower of the Year, Clethra alnifolia (Sweet Pepperbush), and explores the diversity of mycorrhizae in a closely related family, Ericaceae.
Upside-Down Anthers Of Clethra Stand Out, W. John Hayden
Upside-Down Anthers Of Clethra Stand Out, W. John Hayden
Biology Faculty Publications
For the most part, the flowers of the 2015 VNPS Wildflower of the Year, Clethra alnifolia (Sweet Pepperbush), are unremarkable. Five separate sepals, 5 sepa rate petals, 10 stamens in 2 whorls, and a 3-carpellate superior ovary—an organization that can only be considered prosaic among the dicots. One floral feature, however, stands out: the anthers in the open flowers are upside-down! (See Figure 1A.) Further, these upside-down anthers open by pores (Figures 1B, 1C) rather than longitudinal slits, as in most flowering plants. These pores initially form on what would normally be the lowermost extremity of the anther, the inversion …
Little Things Reveal The Big Picture, W. John Hayden
Little Things Reveal The Big Picture, W. John Hayden
Biology Faculty Publications
As enthusiasts who enjoy native plants in natural habitats, we tend to focus on gross morphology— aspects of plant form that can be readily observed with the naked eye or with a hand lens. And there is plenty to see at the gross level. The Flora of Virginia contains 1,269 pages of keys and descriptions devoted to gross morphology of the commonwealth’s botanical treasures. Morphological diversity, however, does not stop at the magnifi cation limit of a hand lens. Light and electron microscopes open up whole new worlds of intricate structure for appreciation and study. And tiny structural details can …
Native Orchids In Winter?, W. John Hayden
Native Orchids In Winter?, W. John Hayden
Biology Faculty Publications
A very special place in Southwest Virginia will soon expand its borders, thanks in part to the annual fundraising appeal by the Virginia Native Plant Society. The Cedars Natural Area Preserve supports ex ceptional natural communities including rocky, dry limestone glades and woodlands located across nearly 20 square miles in Lee County near the Powell River. The karst landscape, where thin soils develop over easily dissolved limestone bedrock, creates terrain that tends to be rolling, rocky, rugged, and full of sinkholes, caves, and sinking streams. The preserve is a haven for rare plants that have adapted to the mostly thin, …
2015 Virginia Wildflower Of The Year: Sweet Pepperbush, Clethra Alnifolia, W. John Hayden
2015 Virginia Wildflower Of The Year: Sweet Pepperbush, Clethra Alnifolia, W. John Hayden
Biology Faculty Publications
Clethra alnifolia is a rhizomatous shrub with aerial stems from 1 to 3 m tall. Leaves are simple, alternate, and bear stellate hairs; petioles are short, 5–10 mm long; leaf blades are obovate to oblong, 5–10 cm long, with relatively blunt apices, cuneate (wedgelike) bases, and margins that are entire toward the base but finely serrate above the middle; venation is pinnate with secondary veins that extend to leaf margins. Stipules are lacking. Flowers are borne on erect terminal racemes that may be solitary or accompanied by additional racemes terminating few-leaved branches arising from upper nodes. Raceme axes and pedicels …
Two Honeysuckles: A Tale Of Dr. Jekyll And Mr. Hyde, W. John Hayden
Two Honeysuckles: A Tale Of Dr. Jekyll And Mr. Hyde, W. John Hayden
Biology Faculty Publications
There are about 180 species of Lonicera (honeysuckles) widely distributed in the north temperate zone. These are mostly shrubby plants, but in Virginia, we have two species that are woody vines (lianas). These two lianous honeysuckles should be familiar to all Virginia Native Plant Society members. One is this year’s VNPS Wildflower of the Year, Lonicera sempervirens (coral honeysuckle), and the other is Lonicera japonica (Japanese honeysuckle), widely and deservedly reviled as one of our most aggressive invasive exotic species. Together, these two plants make an odd pair, a sort of botanical Dr. Jekyll and Mr. Hyde. What is it, …
2014 Virginia Wildflower Of The Year: Coral Honeysuckle, Lonicera Sempervirens, W. John Hayden
2014 Virginia Wildflower Of The Year: Coral Honeysuckle, Lonicera Sempervirens, W. John Hayden
Biology Faculty Publications
The flashy red flowers of coral honeysuckle beckon hummingbirds to their sweet nectar. Coral honeysuckle is a twining woody vine, usually climbing on other vegetation but sometimes trailing along the ground; older stems have papery-brown exfoliating bark.
Incorporating Risk Of Reinvasion To Prioritize Sites For Invasive Species Management, Todd R. Lookingbill, Emily S. Minor, Nadia Bukach, Joseph R. Ferrari, Lisa A. Wainger
Incorporating Risk Of Reinvasion To Prioritize Sites For Invasive Species Management, Todd R. Lookingbill, Emily S. Minor, Nadia Bukach, Joseph R. Ferrari, Lisa A. Wainger
Geography and the Environment Faculty Publications
The relationship between landscape pattern and the distribution and spread of exotic species is an important determinant of where and when management actions are best applied. We have developed an interdisciplinary approach for prioritizing treatment of harmful, nonnative, invasive plants in National Park landscapes of the Mid-Atlantic USA. The approach relies upon a detailed model of reinvasion risk that combines information on: (1) global factors representing park-level infestation from seed and sprout, (2) landscape factors including disturbance-based spread vectors and neighborhood seed density, and (3) local factors determining establishment probability based on habitat suitability. Global seed rain estimates are derived …
Redbud Seedpods Hold Surprises, W. John Hayden
Redbud Seedpods Hold Surprises, W. John Hayden
Biology Faculty Publications
As fall advances across the Old Dominion, canopies of redbud, the 2013 VNPS Wildflower of the Year, transform themselves from green to gold, revealing seed pods also changing color from pale green to dark chocolaty brown. These seedpods, which may be retained on the tree into winter, are typical legume fruits, the product of the flower’s simple pistil, each containing several seeds. Unlike most legumes, however, redbud seed pods seem disinclined to open and release individual seeds for dispersal. Redbud fruits tend to disperse intact. Once on the ground, the inevitable action of weather and microbes gradually degrades the pod, …
2013 Virginia Wildflower Of The Year: Redbud, Cercis Canadensis, W. John Hayden
2013 Virginia Wildflower Of The Year: Redbud, Cercis Canadensis, W. John Hayden
Biology Faculty Publications
Redbuds are small trees or shrubs that may attain heights of 10 m or so. Leaves are alternate and two-ranked, simple, entire, deciduous, broadly cordate, with an acute apex, 611 cm long, 712 cm wide, and palmately veined. Petioles have two swollen pulvini, one at its connection with the stem, the other at its junction with the leaf blade.
Redbud Cauliflory: The Inside Story, W. John Hayden
Redbud Cauliflory: The Inside Story, W. John Hayden
Biology Faculty Publications
One of the most distinctive features of redbuds, Cercis canadensis, the 2013 VNPS Wildflower of the Year, is its production of flowers on mature trunks and major branches, a habit termed cauliflory. Redbud flowers also form on young, one-year old twigs; as explained below, twig- and trunk-borne flowers are parts of a single developmental continuum; twigs bearing flowers eventually becoming trunks and large branches that continue to bear flowers.
Closely Paired Flowers Produce Single Fruit, W. John Hayden
Closely Paired Flowers Produce Single Fruit, W. John Hayden
Biology Faculty Publications
Perhaps one of the most striking features of partridge berry (Mitchella repens), the 2012 VNPS Wildflower of the Year, is its closely paired flowers that yield a single berry fruit (figure 1). That these fruits are double structures, formed by pairs of flowers, is revealed in the presence of two discrete rings of five sepals each on the fruit apex, or in some cases, by a single ring of 10 sepals. Viewed in isolation, without context, the nature of these double fruits may seem perplexing, but as in so many things, a comparative perspective helps to make sense …
Partridge Berry: Simple Beauty Belies Complexity, W. John Hayden
Partridge Berry: Simple Beauty Belies Complexity, W. John Hayden
Biology Faculty Publications
Superficially, plants seem so simple. Rooted in place, they do not move around. And while plant growth is a dynamic process, without time-lapse photography, growth events are so imperceptibly slow that, to us impatient humans, plants seem both immobile and static. Nevertheless, there is a lot going on inside the plant body, and this is especially true for the events of reproduction that play out inside flowers and fruits. As one of my students recently commented, “I used to think it was just a matter of pollen plus stigma and, presto-change-o, seeds happen.” That student, I hope, learned otherwise, as …
2012 Wildflower Of The Year: Partridge Berry, Mitchella Repens, W. John Hayden
2012 Wildflower Of The Year: Partridge Berry, Mitchella Repens, W. John Hayden
Biology Faculty Publications
Although partridge berry is a small and creeping herb, its jewel-like beauty rewards attentive naturalists year-round.
Light Management Important Factor For Partridge Berry, W. John Hayden
Light Management Important Factor For Partridge Berry, W. John Hayden
Biology Faculty Publications
Factors essential for plant life include adequate levels of light, moisture, mineral nutrients, and temperature; though the list is small, each is crucial for survival. This article is a contemplation of how one of these critical factors, light, impacts the biology of our 2012 Wildflower of the Year, Mitchella repens, partridge berry. Aside from issues of reproductive biology, ecological literature on partridge berry is meager. Consequently most of what follows is derived from general works on woodland ecology, perusal of which provides sufficient insight about the biology of Mitchella to inspire ideas worthy of further study.
Oak Galls: A Strange Biology Indeed!, W. John Hayden
Oak Galls: A Strange Biology Indeed!, W. John Hayden
Biology Faculty Publications
Anyone who takes the time to look closely at several branches of oak will soon find one or another peculiar anomaly among the leaves and twigs. One can easily find structures resembling Ping-Pong balls, hard knots, fluffy tufts, horns—either single or clustered, or irregular thickenings, to mention just a few possibilities. These abnormal growths are galls, structures caused by the presence of small insect larvae living inside the tissue of the plant. Galls can be found on a wide variety of plants. They are common, for example, on the stems of goldenrods, and the leaves of maples, but oaks are …
Hybrid Oaks: Full Of Vexation And Wonder, W. John Hayden
Hybrid Oaks: Full Of Vexation And Wonder, W. John Hayden
Biology Faculty Publications
Distinguishing different species of oak in the forests of eastern North America can be challenging. For one thing, there are simply a lot of different species to sort out. A recent reference (Stein et al. 2003), describes 50 species in the genus Quercusoccurring naturally east of the 100th meridian, and 90 species are distinguished for all of North America north of Mexico (Nixon 1997). With so many species to parse, confident identification requires careful study of leaves, stem and leaf hairiness, and fully mature acorns with their caps. But care is not always enough, because in addition to the …
2011 Wildflower Of The Year: White Oak, Quercus Alba, W. John Hayden
2011 Wildflower Of The Year: White Oak, Quercus Alba, W. John Hayden
Biology Faculty Publications
Emblematic of strength and longevity, white oaks grace the deciduous forests of eastern North America.
Don't Judge A Book By Its Cover: The Curious Case Of Wild Ginger Pollination, W. John Hayden
Don't Judge A Book By Its Cover: The Curious Case Of Wild Ginger Pollination, W. John Hayden
Biology Faculty Publications
What pollinates wild ginger? This seems like an easy question. The inconspicuous little flowers are held close to the forest floor, often completely hidden by a dense canopy of ginger leaves above. Flower color is rather drab, dominated by brown and maroon hues. Wind pollination seems completely unlikely and flowers pollinated by bees, butterflies, moths, or hummingbirds are always much more showy and accessible to these flying creatures. Flies, however, given their natural inclination to seek carrion as a food source for their babies (i.e. maggots), are often attracted to brown and maroon flowers. And because their actual quarry, animal …
2010 Wildflower Of The Year: Wild Ginger, Asarum Canadense, W. John Hayden
2010 Wildflower Of The Year: Wild Ginger, Asarum Canadense, W. John Hayden
Biology Faculty Publications
Wild ginger is a low herbaceous plant. The stem consists of a branched creeping rhizome at or just below the soil surface. Soft-hairy leaves arise in pairs annually from rhizome branches. Petioles can be up to 20 cm long, elevating the 7—25 mm wide kidney-shaped leaf blades above the forest floor. Small flowers appear in the spring shortly after the leaves have expanded. Typically, one must push the leaves aside in order to glimpse the jug-like flowers. A single flower stalk appears between the paired leaf bases, but it is short and barely lifts the flower above the soil surface. …
Hunker Down And Hold On: Contractile Roots Give Skunk Cabbage Another Special Trait, W. John Hayden
Hunker Down And Hold On: Contractile Roots Give Skunk Cabbage Another Special Trait, W. John Hayden
Biology Faculty Publications
I can remember the first time I ever heard of contractile roots. It was in graduate school at the University of Maryland and a friend of mine was busy preparing a lecture on roots. He said to me something like “Did you ever notice, while pulling up dandelions, that the darn weed seems to be pulling back? As it turns out, it is!” Strange but true, dandelions, along with a diverse assemblage of other species, have contractile roots that serve to pull the plant downward. In this capacity, contractile roots go well beyond the routine function of providing anchorage for …
2009 Wildflower Of The Year: Skunk Cabbage, Symplocarpus Foetidus, W. John Hayden
2009 Wildflower Of The Year: Skunk Cabbage, Symplocarpus Foetidus, W. John Hayden
Biology Faculty Publications
Skunk cabbage is a coarse herbaceous plant. The stem consists of a stout rhizome oriented vertically in the soil. Leaves and flowers arise from the tip of the rhizome which is often not visible, resulting in the appearance of leaves and flowers arising directly from the swampy mires where these plants grow. Flowers appear during the winter, long before the leaves. The flowers are minute, clustered into a ball-like group (spadix) almost entirely enclosed by a fleshy, hood-like, spathe. The spathe ranges from 8 to 15 cm in height, is more or less pear-shaped, widest near the bottom, and tapers …
Skunk Cabbage Flowers: The Heat Is On, W. John Hayden
Skunk Cabbage Flowers: The Heat Is On, W. John Hayden
Biology Faculty Publications
It is a remarkable sight, as striking as it is unexpected: January skunk cabbages emerging from the frozen mires they call home, melting their way through snow and ice. It seems so improbable because in everyday experience plants exist at equilibrium with ambient temperatures. Leave an apple on the front seat of your car in summer, it gets hot; examine your tomato plants on that first frosty morning in autumn, and they are permeated with ice crystals. People, mammals and birds are inherently warm, and pretty much nothing else is. Except, of course, for the exceptions, of which skunk cabbage …
Spiderworts: Not Just Another Pretty Face For Science, W. John Hayden
Spiderworts: Not Just Another Pretty Face For Science, W. John Hayden
Biology Faculty Publications
Species of Tradescantia, or spiderworts, are handsome plants. Several wild species, including the VNPS wildflower of the Year for 2008 (T. virginiana), can be found in eastern North America and additional species grace gardens, and hothouse conservatories. Spiderworts are not, however, just a bunch of pretty faces. Spiderworts have a long history of service to science, both in terms of teaching and pure research.
2008 Wildflower Of The Year: Virginia Spiderwort, Tradescantia Virginiana, W. John Hayden
2008 Wildflower Of The Year: Virginia Spiderwort, Tradescantia Virginiana, W. John Hayden
Biology Faculty Publications
Spiderwort is an herbaceous perennial that arises from a cluster of rather stout overwintering roots. Stems may be solitary or more commonly clumped, and usually grow unbranched, reaching heights up to 40 cm tall. Stems are smooth or bear scattered short hairs. Leaves are 2—5 per stem, attached by means of a leaf sheath that is 13 cm long. Leaf blades are dull green, elongate, ending in a gradually tapered tip, flat or keeled, smooth (without hairs), and 1—3.5 dm long by 0.5—2.5 cm wide. Flowers occur in tight clusters located at the stem apex; bracts similar to the leaves …