Polypodium Virginianum Research Articles

Sustained zeaxanthin-dependent thermal dissipation is induced by desiccation and low temperatures in the fern Polypodium virginianum.

Desiccation and low temperatures inhibit photosynthetic carbon reduction and, in combination with light, result in severe oxidative stress, thus, tolerant organisms must utilize enhanced photoprotective mechanisms to prevent damaging reactions from occurring. We sought to characterize the desiccation tolerance of the fern Polypodium virginianum and to assess the role of the xanthophyll cycle and sustained forms of thermal dissipation in its response to desiccation, as well as to low temperatures during winter. Our results demonstrate that P. virginianum is desiccation-tolerant and that it increases its utilization of sustained forms of zexanthin (Z)-dependent thermal dissipation in response to desiccation and low temperatures during winter. Experiments with detached fronds were conducted in dark and natural light conditions and demonstrated that some dark-formation of Z occurs in this species. In addition, desiccation in the light resulted in more pronounced declines in maximal photochemical efficiency (Fv /Fm ) and higher Z levels than desiccation in the dark, indicating a substantial fraction of the sustained reduction in Fv /Fm is due to Z-dependent sustained dissipation. Recovery from desiccation and from low temperatures exhibited biphasic kinetics with a more rapid phase (1-4 h), which was accompanied by an increase in minimal fluorescence yield (Fo ) but no change in Z, and a slower phase (up to 24 h) correlating with reconversion of Z to violaxanthin. These data suggest that two mechanisms of sustained thermal dissipation occur in response to desiccation and low temperatures, possibly corresponding to sustained forms of the energy-dependent and zeaxanthin-dependent mechanisms of dynamic thermal dissipation.

Beyond antheridiogens: chemical competition between gametophytes ofPolypodium appalachianumandPolypodium virginianum

To understand the mechanisms by which fern gametophytes compete and the consequences of their interactions, we studied the effects of intraspecific and interspecific chemical competition on spore germination, sexual development, and gametophyte size in two closely related and co-occurring species of Polypodium from eastern North America. We cultured gametophytes of diploid Polypodium appalachianum Haufler & Windham and tetraploid Polypodium virginianum L. and recorded spore germination, sexual development, and gametophyte size and growth rates in a series of treatments representing different levels of competition within and between the two species. We found that mature gametophytes of both species reciprocally inhibit spore germination, sexual development, and growth of neighboring plants; we show that these effects are due to chemical interactions and not competition for resources. Competitive effects on spore germination and sexual development are similar for within- and between-species interactions, but repression of growth and gametophyte size is greater when competing gametophytes are heterospecific. An additional mechanism of intergametophytic competition via proliferous vegetative growth is also reported. We conclude that gametophytes of these species interact through a novel context-dependent chemical system that is independent from sex expression-regulating pheromones (antheridiogens). Our findings indicate that inhibition of growth and development among fern gametophytes is not solely a side effect of antheridiogens, as is generally thought.

The Plant Species Composition and Phytogeographical Significance on Algific Talus Slope in Korea

Algific talus slopes are lacal cold micro-environmental habits where cool air escapes through vents and fissures of talus layer, and ice forms in summer. To access the phytogeographical significance and to develop the conservation strategy on vegetation of the algific talus, plant species composition on seven algific talus in South Korea was investigated. As a results, phytogeographically significant northern elements such as Cystopteris fragilis (L.) Bernh., Diplazium sibiricum (Turcz. ex Kunze) Sa.Kurata, Polypodium virginianum L., Vaccinium vitis-idaea L. and Hackelia deflexa (Wahlenb.) Opiz were distributed in these algific talus slopes (below N37˚43'). In addition, subalpine species such as Woodsia subcordata Turcz, Rosa suavis willd., Clematis fusca var. coreana (H.Lev. & Vaniot) Nakai, Calamagrostis langsdorfii (Link) Trin. and Carex vaginata var. petersii (C.A.Mey.) Akiyama were also distributed as typical relictual species of these algific talus (less than alt. 400m). The algific talus slopes in Korean peninsular can be regarded as the insular refugia that northern plant species advanced southward during the latest glacial age have been isolated and adapted in some local microhabitats. Because the algific talus slopes as paleorefugia are very important in terms of phytogeography as well as meteorology ans geology, developments of strategies for in situ and ex situ conservation on these small isolated and threatened populations associated with the algific talus urgently needed.

A Comparison of Physiological and Morphological Properties of Deciduous and Wintergreen Ferns in Southeastern Pennsylvania

Physiological and morphological properties of a deciduous, perennial fern (Onoclea sensibilis) and three wintergreen, perennial ferns (Polystichum acrostichoides, Polypodium virginianum, and Dryopteris intermedia) were examined using leaf fluorescence, chlorophyll a:b ratios, total chlorophyll content, water potential, and leaf edge to surface area ratios. Onoclea sensibilis differed significantly from the wintergreen ferns in morphology and physiology for almost every parameter measured. Interspecific differences were also observed within the wintergreen group. Dryopteris intermedia differed most within the wintergreen group and showed more similarity in physiology to O. sensibilis. Dryopteris intermedia was found occupying the same high-light, higher soil moisture habitat as O. sensibilis, which may indicate that inherent leaf morphology, physiological characteristics, and a wintergreen or perennial life cycle, play im- portant roles in determining habitat preference.

Characterization of Protein Synthetic Changes in a Desiccation-Tolerant Fern,Polypodium virginianum. Comparison of the Effects of Drying, Rehydration and Abscisic Acid

The desiccation-tolerant fern, Polypodium virginianum, was able to lose more than 60% of its fresh weight during periods of prolonged water stress and fully recover during periods of water availability. Rehydration from the air-dry state occurred rapidly (within 24 h) with a concurrent initiation of protein synthesis. A low-molecular-weight doublet was synthesized during water stress and was stable for at least 24 h after rehydration. These proteins were expressed also when the fully hydrated fronds were subjected to exogenous ABA even though drying resulted in a 10-fold reduction in ABA content. The large subunit of Rubisco was synthesized during drying, but despite temporary accumulation, the de novo synthesized component was degraded during rehydration

Abscisic Acid Enhances the Ability of the Desiccation-Tolerant FernPolypodium virginianumto Withstand Drying

Detached fronds of Polypodium virginianum L. survived loss of 65-70% of their fresh weight over 10 d of slow-drying. Drying over silica gel resulted in a faster rate of water loss, to a lower fresh weight, which the fronds did not survive. When fronds were incubated in abscisic acid for 24 h prior to silica-drying, the amount of water lost was reduced, resulting in survival of the fronds upon subsequent rehydration. Incubation in abscisic acid for at least 18 h was necessary for survival. Fronds in which the final fresh weight after drying was below a critical amount (i.e. to less than 25% original fresh weight) did not survive. A reasonable correlation could be drawn between electrolyte leakage upon rehydration and survival of some desiccation treatments, although this was not always clear-cut, especially in fronds incubated in abscisic acid for an insufficient time to ensure survival. Several polypeptides were synthesized during slow- and silica-drying, and in response to abscisic acid. No novel polypeptides were identified that were unique to the desiccation regimes which resulted in survival. Nor did ABA induce specific proteins in fronds desiccated after preincubation in this regulator for 24 h.

Photosynthetic response to sunflecks in the desiccation-tolerant fern Polypodium virginianum

The photosynthetic response to sunflecks was investigated in the fern Polypodium virginianum growing on cliff edges of the Niagara Escarpment, in southern Ontario, Canada. Ferns were exposed to natural precipitation, continuous watering, or continuous drought prior to exposure to artificial sunflecks. The results were analyzed using temperature, humidity and previous exposure to light as covariates. The response to sunflecks was extremely rapid and showed no measurable induction period in the field. Controlled experiments completed in the laboratory showed exceptionally short induction periods. Previous exposure to sunflecks, and desiccation did not influence the time constants of response to sunflecks although drying did reduce maximum rates of CO2 exchange. Polypodium virginianum shows an extremely rapid response to fluctuations in the supply of light, and this is interpreted to be advantageous to this species because of the array of extremely hostile conditions that occur at cliff edges.

Seasonal changes in photosynthesis in the desiccation-tolerant fern Polypodium virginianum.

Seasonal changes in photosynthesis were examined in the desiccation-tolerant fern Polypodium virginianum growing in a forest understory along cliff edges of the Niagara Escarpment in southern Ontario, Canada. For plants growing in situ, the photosynthetic response to irradiance was examined on a seasonal basis, to determine the degree to which the utilization of light changed over the growing season. Experiments were executed on control plants, on previously desiccated then rehydrated plants, and on continuously hydrated plants to determine if prior desiccation influenced the response to light. Soil and xylem water potential and temperature were monitored and used as covariates in analyses. The results showed that carbon gain in the spring greatly exceeded that of any other season. Despite this, there was little change in the photosynthetic response to light on a seasonal basis even though plants were exposed to highly variable and highly limited light most of the time. Prior desiccation had a slight influence on photosynthetic rate but not on other photosynthetic parameters such as the light compensation point and Lhalf. Temperature was a significant seasonal covariate and additional experiments conducted in the laboratory showed that the response of photosynthesis to temperature was broad. Xylem water potential was correlated with seasonal changes in relative humidity. The results suggest that P. virginanum persists in hostile cliff-edge habitats by being able to exploit high-light periods in the spring and by thereafter maintaining a low but relatively constant rate of carbon despite prior exposure to fluctuating supplies of light and water.

CHROMOSOMAL ANALYSES AND THE ORIGIN OF ALLOPOLYPLOID POLYPODIUM VIRGINIANUM (POLYPODIACEAE)

Polypodium virginianum L. has been treated as a morphologically and chromosomally variable species. Recently, however, two species have been named from within the P. virginianum complex. Chromosome counts reported here confirmed that these segregate species, P. appalachianum Haufler and Windham and P. sibiricum Siplivinskij, are diploids with n = 37. It was further hypothesized that hybridization between these diploids initiated the allotetraploid P. virginianum. Naturally occurring, sterile triploid plants obtained from habitats in which the putative allotetraploid was sympatric with its presumed diploid progenitors have been verified isozymically as backcross hybrids. Meiotic chromosomal behavior showed that the triploids contained univalents and bivalents in nearly equal numbers, confirming that tetraploid P. virginianum contained one genome from each diploid. Observation of three to six trivalents in triploid preparations suggested that the diploids are still closely related genetically. This hypothesis was supported by isozymic studies which found a genetic identity of 0.610 between P. appalachianum and P. sibiricum, a value much higher than the average identity for congeneric fern species studied to date (0.33) and higher than any other species pair in the P. vulgare L. complex (average I = 0.307). These chromosomal and isozymic data help to resolve a biosystematic riddle that has interested pteridologists for over 40 years.

Electrophoretic Evidence for Allopolyploidy in the Fern Polypodium virginianum

Polypodium virginianum comprises three morphologically similar cytotypes: diploid (2n = 74), triploid (2n = 111), and tetraploid (2n = 148). Previous cytological and morphological analyses suggested that tetraploid P. virginianum was actually of allopolyploid origin resulting from hybridization between diploid P. virginianum and another diploid Polypodium species. To test this, an electrophoretic investigation of diploid, triploid, and tetraploid populations of P. virginianum was undertaken. Analysis of eight enzymes showed 15 loci common to all three cytotypes. Fixed heterozygosity due to the presence of two additional isozymes was detected in triploid and tetraploid P. virginianum. This increase in isozyme number in the tetraploid is suggestive of the addition of two divergent genomes in its formation. One of the parental genomes involved in the formation of tetraploid P. virginianum clearly is diploid P. virginianum; the second parental genome appears to be P. amorphum. Electrophoretic data are in agreement with 1) an allopolyploid origin of tetraploid P. virginianum, and 2) formation of the triploid cytotype via hybridization between diploid and tetraploid P. virginianum.

TYPIFICATION WITHIN THE POLYPODIUM VIRGINIANUM COMPLEX (POLYPODIACEAE)

SummaryThe validity and application of specific and varietal names in the Polypodium virginianum complex were investigated. Lectotypification of both P. virginianum L. and P. vulgare L. var. americanum Hooker is proposed, the former based on a plate in Morison and the latter on a collection by Percival at Kew. On morphological grounds, the types of both taxa appear to represent the tetraploid race in the complex. Hooker's variety therefore becomes a later synonym of the Linnaean species. Polypodium vinlandicum Löve and Löve was based on the type of Hooker's variety and thus is also synonymous with the tetraploid cytotype of P. virginianum. The name Polypodium “oreophilum” has sometimes been accepted as a legitimate name for some West Virginian plants in the complex. The combination, however, was never validly accomplished and so must be rejected. Furthermore, the use of the epithet for any member of this group is now prohibited by the South American P. oreophilum Maxon.

A comparative study of sporophyte morphology of the three cytotypes of Polypodium virginianum in Ontario

There are three cytotypes of Polypodium virginianum L. in Ontario. These may be identified by macro- and micro-morphological characters. The most useful characters for identification are frond shape, tip lobing, shape of segment apices, spore size, cell size, and number of paraphyses per sorus. The triploid cytotype, which often overlaps the variation shown by the diploid and tetraploid, can be recognized by a high percentage of aborted spores.

Saxicolous Bryophyte and Macrolichen Associations in Southern Illinois. II. Panther's Den, Union County

This is the second in a series of papers analyzing the bryophytemacrolichen flora of sandstone canyons in southern Illinois. Nineteen species of mosses, twenty-one species of hepatics and 6 macrolichen elements were found within 4 study areas in Panther's Den, Union County, Illinois. For each of the above, frequency, basal area, relative cover and importance value were calculated. This information, combined with similarity coefficients, indicates a range of microhabitat conditions which create a flora dominated by common southern Illinois species. It also includes some unusual taxa. As in an earlier study differences in aspect and vertical stratification appear to be significant factors affecting species distribution. Panther's Den is located in the extreme northeastern corner of Union County, Illinois (T11S RIE NE 10), southeast of Little Grand Canyon and within the unglaciated Greater Shawnee Hills Section of the Shawnee Hills Division (Stotler, 1976, Fig. 1). It is the second isolated ravine to be systematically sampled in a continuing study of the saxicolous bryophyte and macrolichen associations of southern Illinois. The ravine runs north and south and is bordered to the east and west by low bluffs and hills. To the east of the ravine, there is an area of massive block-faulted Pennsylvanian sandstone. The juxtaposition of the walls forms a sheltered area which gives Panther's Den its name. Many of the walls produce seepage which keeps them moist during dry weather. Additionally, evaporation is reduced since the walls are shaded by each other and by vascular plants. This shelter produces a microclimate which is cooler and more moist in the summer and warmer in the winter than the surrounding area. Because of their sheerness and lack of soil, the walls support few vascular plants except for scattered individuals of Heuchera parviflora Barth. and Polypodium virginianum L. The bryophyte and macrolichen flora, however, is diverse and abundant. Within the flora are both common, thoroughly expected elements of the region, as well as rarer, more isolated taxa which appear to be at the extremes of their ranges. Although this ravine bears some superficial resemblance to Little Grand Canyon, its floristic composition is different. Hence, a quantitative study here should broaden the data pool for the southern Illinois area. 1A portion of a Research Report submitted by the first author to The Graduate School of Southern Illinois University in partial fulfillment of the requirements for the degree of Master of Science in Biological Sciences. 2 Botany Department, Southern Illinois University, Carbondale, Illinois 62901. This content downloaded from 157.55.39.255 on Wed, 25 May 2016 05:59:39 UTC All use subject to http://about.jstor.org/terms 1977] WEST & STOTLER: SAXICOLOUS ASSOCIATIONS IN ILLINOIS 613

The sorus of Polypodium virginianum: some aspects of the development and structure of paraphyses and sporangia

A comparative study of the ontogeny of sporangia and paraphyses showed that these organs are homologous, with divergence in structure and function occurring after several divisions in the initials of these organs. Paraphyses develop an elongated stalk bearing several vesiculated cells, most of which bear appendages or glandular hairs. Sporangial initials form stalks that subtend the sporangium or spore case enclosing cells which undergo meiosis to form spores. The stalk and vesiculated cells of each paraphysis have a rather complex cytoplasm in the early stages of ontogeny, but ultimately these cells become vacuolated with large deposits of tannins. The tannin bodies originate in small cytoplasmic vacuoles which appear to fuse, forming larger vacuoles with tannin deposits. Stalk and annulus cells of the sporangia also form vacuoles with tannin inclusions. The appendages of the vesiculated cells remain cytoplasmic much longer than the subtending vesiculated cells, but eventually they vacuolate and form tannins as well. It is suggested that the paraphyses perform a protective function for the developing sorus to prevent the loss of water from the developing sporangia.

A comparative study of gametophyte development of the diploid and tetraploid races of Polypodium virginianum

Three different cytotypes, diploid, triploid, and tetraploid, occur within the fern species Polypodium virginianum or rock polypody. Previous studies have shown morphological differences in the sporophyte and this study was undertaken to determine the distinctiveness of the gametophyte of these cytotypes. The cytotypes differ in several developmental features: percentage of viable spores produced, time required for germination to take place, and time required for the gametophytes to reach sexual maturity. Of the three cytotypes, the tetraploid had a higher germination rate and considerably faster rate of development than either the diploid or triploid. The triploid showed a high percentage of aborted spores and a slow and irregular development of the gametophyte.

Occurrence of the European Polypodium australe Fee on San Clemente Island, California

These include Polypodium virginianum L., with diploid and tetraploid races, occurring from the eastern seaboard to British Columbia; P. hesperium Maxon, a species also with diploid and tetraploid races, found from British Columbia south to Arizona; P. glycyrrhiza D. C. Eaton, a diploid species, distributed from central California north to Alaska; P. scouleri Hook. & Grev., a diploid coastal species which is the most distinct of the complex, occurring only on Guadalupe Island, Santa Cruz Island, Morro Rock in the southern portion of its range and on the mainland 56

Contributions to the cytology and taxonomy of species of Polypodium in Europe and America. I. Cytology

The paper summarizes the present state of cytogenetic knowledge of Polypodium in Europe and some parts of America, and discusses the evidence regarding the phyletie relations of the various taxa. New observations on wild European hybrids include (a) descriptions and analysis of chromosome pairing in two tetraploids believed to represent crosses between diploid and hexaploid, and (6) further observations on chromosome pairing in triploids. All possible types of hybrid between the three European taxa have been synthesized and chromosome pairing in them seen. In every case there is close agreement with the corresponding observations on wild plants. It is concluded that the hexaploid is in origin an amphidiploid hybrid between the European tetraploid and the European diploid as previously postulated, and that the two parental types are not otherwise closely related. Specific recognition for the three European cytotypes is recommended and names for them have been found in accordance with the International Rules of Nomenclature. A parallel study of Polypodium virginianum from eastern America has shown that diploid P. virginianum is able to pair chromosomes with one of the genomes present in European tetraploids and hexaploids. This genome is also present in tetraploid P. virginianum from eastern America as half the nuclear content. It is therefore concluded that not more than four different genomes are present, separately or combined, among the various taxa discussed, two of which have been identified singly in existing diploid species on opposite sides of the Atlantic. Preliminary observations on a diploid from western America (P. glycyrrhiza) have shown that this also is related to at least one of the European polyploids although the exact nature of the relationship is still under study.

Two cytological forms of Polypodium virginianum in eastern North America.

P. virginianum L. is the only representative of the P. vulgare complex which is known to occur on the eastern seaboard of North America. It has hitherto been regarded as a well-characterized species readily distinguishable from all others by the possession of a striking type of stellate paraphysis which has been intensively studied by Martens1 and his collaborator, who regard them as modified sporangia. The chromosome number has previously been reported by one of us to be diploid2.

A Crispate Variant of the Christmas Fern

Some years ago the late Albert F. W. Vick, founder of Vick's Wild Gardens, showed me in the woods of the property east of Glenmoore, Pennsylvania, where he raised native plants for the trade, a large colony of an unusually attractive Christmas Fern. The margins of the pinnae are jaggedly cut, with the teeth tending to widen upward and curl so as partly to overlap. This presumably corresponds to what was named by Clute in 1901 Polystichum acrostichoides var. crispum (mistakenly cited as forma crispum in Broun's In 7 Devlin is here reproduced. This shows how the pinnae are gradually reduced upward, without 9 s 9 yany sori being produced. Similar types of cutting accompany lack of fertility in certain other species, as Asplenium platyneuron var. or f. Hortonae, Polypodium virginianum f. cambricoides, and some Boston Ferns.

The Ferns and Fern Allies of Kentucky (Concluded)

2. POLYPODIUM VIRGINIANUM Linnaeus (Common Polypody). Polypodium vulgare of authors, not Linnaeus. Common. On sandstone. One instance growing on a tree some forty feet from the ground. Bath, Bell, Boyd, Carter, Christian, Edmonson, Elliott, Floyd, Greenup, Laurel, Madison, McCreary, Morgan, Powell, Rowan, Warren, and Whitley counties. 3. POLYPODIUM POLYPODIOIDES (Linnaeus) Watt (Resurrection Fern). Common. Sandstone and trunks of trees. Boyd, Calloway, Christian, Edmonson, Greenup, Marshall, Oldham, Pulaski, Rowan, Spencer, Warren, and Whitley counties. 4. ADIANTUM PEDATUM Linnaeus (Maidenhair Fern). Common. Moist shade, rich leaf mold. Anderson, Bath, Bell, Boyd, Breathitt, Calloway, Carter, Edmonson, Elliott, Graves, Greenup, Harlan, Jessamine, Laurel, Madison, McCreary, Morgan, Powell, Pulaski, Rowan, and Whitley counties. 5. ADIANTUM CAPILLUS-VENERIS Linnaeus (Southern Maidenhair). Rare. Dripping limestone. One specimen in Gray Herbarium labelled, Aug. 1899Carter Caves, Ky,-(G. G. Jr.)? One specimen found in Boyd County, but the only known station at present is in Pulaski County. 101