A contribution to the knowledge of the pteridosperm genera Pseudomariopteris Danzé-Corsin nov. emend. and Helenopteris nov. gen

The macromorphology and epidermal anatomy of three Late Carboniferous-Early Permian pteridosperm species, conventionally assigned to the form-genus Pseudomariopteris Danzé-Corsin, are described from the Stephanian of the Blanzy-Montceau Basin (Central France). The generic diagnosis of Pseudomariopteris is emended, and P. busquetii is designated as the type species of the genus. The combination P. cordato-ovata (Weiss) Gillespie et al. is validated to replace the illegitimate name P. ribeyronii (Zeiller) Danzé-Corsin. The species diagnoses of P. busquetii and P. cordato-ovata are emended. On the basis of its epidermal anatomy, P. paleaui, another species orininally described from Central France, is transferred to the newly established genus Helenopteris Krings et Kerp, and the new combination Helenopteris paleaui is introduced. Lectotypes of P. busquetii and H. paleaui are selected. In addition, specimens from other basins are (re-)examined and illustrated. Seeds attached to a P. busquetii specimen suggest a callistophytalean relationship for Pseudomariopteris. Compression fossils and cuticles of Pseudomariopteris and Helenopteris are interpreted in terms of palaeoecology: Pseudomariopteris busquetii and P. cordato-ovata had climbing/scrambling growth habits; specialized climber hooks can be demonstrated for both species, either in compression or in cuticular preservation. Although the growth habit of H. paleaui is not yet entirely clear, the size of its fronds suggests that this taxon most probably was also a scrambler/climber. Finally, based on epidermal features, a tentative reconstruction of stages of the pinnule ontogeny of H. paleaui is provided.     

Ant protection of the nectaried fern Polypodium plebeium in central Mexico

Nectaries on fronds of Polypodium spp. have been studied previously only in cultivated specimens. We conducted field observations in middle-elevation forests in Mexico and found five ant species associated with nectaries of Polypodium plebeium and P. lepidotrichum. To investigate whether nectaries promote protection against herbivores, we performed ant-exclusion experiments with nectary-bearing ferns (P. plebeium) and other ferns without nectaries (Polypodium plesiosorum, P. furfuraceum, and Phlebodium pseudoaureum). When ants were excluded from the developing fronds of Polypodium plebeium, damage from foliage-feeding sawfly and lepidopteran caterpillars was significantly greater than in control fronds. Ferns without nectaries did not show a difference in damage between ant-excluded and control fronds. Our results demonstrate that fern nectaries can support ant defense of the plant body as do the extrafloral nectaries of many angiosperms.     

Old fronds serve as a vernal carbon source in the wintergreen fern Dryopteris intermedia (Aspleniaceae)

Maintaining green leaves beyond the growing season has been hypothesized to benefit plants by supplying either a nutrient or a carbon source. Understanding such ecophysiological aspects of plants will help us to appreciate how a species functions in its environment and predict how it might be affected by future changes in that environment. The wintergreen fern species Dryopteris intermedia does not retranslocate nitrogen and phosphorus from old fronds in spring, but photosynthesis does take place in the old fronds during this season. To determine if carbon fixed in the old fronds is translocated to other parts of the plant, we labeled old fronds with (13)C via photosynthetic uptake and examined old fronds, new fronds, fine roots, and rhizomes for (13)C content 1 day and 1 month after labeling the old fronds. Vernally fixed carbon was translocated to the new fronds but not significantly to the below ground tissues. Old fronds in this species, therefore, serve as a carbon source for vernal growth of new fronds. This is the first study in which a fern was labeled with (13)C to track vernally fixed carbon from old fronds to the rest of the plant in a wintergreen species. Future research should examine the precise timing of this carbon movement and examine other species for a similar or contrasting strategy.     

Plant response to overcrowding – Lemna minor example

Plants adopt various strategies in response to increasing density. We tested that response in two populations of Lemna minor L. – a free floating aquatic plant that frequently experiences intraspecific competition for space. Surface area of fronds and colonies, colony size (the number of fronds per colony), the rate of reproduction (based on the number of produced fronds) and growth rate (enlargement of surface area of all colonies) were the analysed factors presumably affected by density. The study was performed in natural stands and in experimental conditions with the use of two contrasting plant densities. Plants growing in natural conditions produced fronds of smaller and less variable surface area as a response to overcrowding but the number of fronds per colony was unrelated to plant density. Stable experimental conditions facilitated formation of fronds and colonies larger than in the field but frond detachment decreasing colony size was more intensive at high than at low density. This strategy allowed plants to more efficiently occupy limited available space. No self-thinning was observed during experimental cultures. Due to increasing frond area in cultures, growth rate was always higher than the rate of plant reproduction. Both were strongly negatively affected by high density. Performed calculations indicate that density-dependent growth inhibition starts when L. minor colonies cover the available water surface with a mono-layer mat. Some types of responses were found to significantly differ between analysed populations, which was also shown by genetic differences tested with he ISSR-PCR technique. Possible causal relationship between plant strategies and their genomic structure needs, however, further studies.     

Field studies of the relationship between herbivore damage and tannin concentration in bracken (Pteridium aquilinum Kuhn)

Summary The acceptance of secondary plant metabolites as herbivore deterrents rests primarily on their deleterious effects on herbivores. Efforts to demonstrate differential fitness in natural plant populations with varying concentrations of tannin have failed, since coevolved plant predators may physiologically or behaviorally circumvent the defense, which results in apparently equal amounts of damage to defended and undefended individuals. In this study, two approaches were used to overcome this difficulty. 1) Theoretically, more energy should be allocated to the defense of parts which contribute more heavily to the plant's fitness. Bracken fern clones produce fronds throughout the growing season. Fronds which are produced early should be more heavily defended than late-emerging fronds which will return less photosynthate per unit cost of production. The results of this study do not support this prediction; it appears that the production of tannin is more closely linked to environmental factors such as water stress than to date of frond emergence. Fronds which emerged in August contained as much tannin as fronds which emerged in May. 2) By recording the temporal occurrence of herbivore damage in bracken ferns, it was found that in fronds which escaped attack until after reaching maturity there was a significant negative correlation between tannin concentration in the frond and the amount of damage experienced. This result supports the generally accepted assumption that herbivory has been a selective force in the evolution of tannin as a defensive substance.     

Giant rhinoceros beetle Golofa claviger (Linnaeus) (Coleoptera: Melolonthidae: Dynastini) is damaging North Brazilian oil palm plantations

The oil palm is an economically important crop cultivated in the North of Brazil. Damage caused by insects is one of the main causes of reduced productivity for the oil palm. Before this research, only the beetles of the family Curculionidae were considered to be oil palm pests in Brazil. However, for the first time, we report on the damage caused by a giant rhinoceros beetle to oil palm plantations in Pará, Brazil. The beetle was identified as Golofa claviger (Linnaeus, 1771), which has a single record in Brazil (Pará) but is widely distributed in South America. The species occurs in an unprecedentedly high abundance of local specimens. The attacks are concentrated on the central cluster of young palms. Feeding behavior is identified as the main cause of the damage as the beetles use their mouthparts to rip the plant tissues, causing wedge-shaped cuts on young fronds that have not yet unfurled. After an attack, the leaflets of the unfurled fronds are partially destroyed.     

Effects of cyanogenesis in bracken fern (Pteridium aquilinum) on associated insects

Abstract. 1. The relationship between cyanogenesis in bracken fern and the insect fauna feeding on the plant was investigated over a 3 year period. The most common insects between May and July, while cyanide levels were high, were the sawflies Strongylogaster impressata Provancher, S.multicincta Norton, Aneug-menus fzavipes (Norton), the aphid Macrosiphum euphorbiae (Thomas) and a microlepidopteran species of Monochroa .
2. Collections of insects from cyanogenic and acyanogenic fronds showed significantly fewer sawflies on the cyanogenic fronds. The aphid and the microlepidopteran were randomly distributed with respect to cyanogenicity.
3. Feeding tests for two of the sawfly species ( Simpressata and Smulticincta ) showed that larvae grew more slowly and had a higher mortality when raised on cyanogenic fronds than on acyanogenic ones.
4. Field collected cyanogenic bracken fronds were found to have sustained less damage from chewing herbivores compared with acyanogenic fronds.     

Phytoremediation of an arsenic-contaminated site using Pteris vittata L.: a two-year study

A field study was conducted to determine the efficiency of Chinese brake fern (Pteris vittata L.), an arsenic hyperaccumulator, on removal of arsenic from soil at an arsenic-contaminated site. Chinese brake ferns were planted on a site previously used to treat wood with chromated copper arsenate (CCA). Arsenic concentrations in surface and profile soil samples were determined for 2000, 2001, and 2002. In both 2001 and 2002, senesced and senescing fronds only, as well as all fronds, were harvested. Frond arsenic concentrations were not significantly different between the three harvests. Compared to senesced fronds, live fronds resulted in the greatest amount of arsenic removal. There were no significant differences in soil arsenic concentrations between 2000, 2001, and 2002, primarily due to the extreme variability in soil arsenic concentrations. However, the mean surface soil arsenic was reduced from 190 to 140 mg kg(-1). Approximately 19.3 g of arsenic were removed from the soil by Chinese brake fern. Therefore, this fern is capable of accumulating arsenic from the CCA -contaminated site and may be competitive, in terms of cost, to conventional remediation systems. However, better agronomic practices are needed to enhance plant growth and arsenic uptake to obtain maximum soil arsenic removal and to minimize remediation time.     

Plant and frond dynamics of the giant kelp,Macrocystis pyrifera,forming a fringing zone in the Falkland Islands

Fluctuations in plant and frond characteristics are described for Macrocystis pyrifera (L.) C. Agardh (Laminariales, Phaeophyta) forming a fringing zone in the Falkland Islands. Giant kelp plants were sampled along a transect in the austral autumn (May 1986) and late spring (December 1986) which, according to previous frond weight analysis, were the times when extremes in population parameters were expected. Plant density and holdfast wet weights were similar for both seasons, but plants had more fronds and the fronds weighed more in spring than in autumn. Consequently, in autumn the frond biomass (1·1 wet kg m^?2) and productivity (34·1 wet g m^?2 d^?1) were lower than in spring, when a biomass of 5·0 wet kg m^?2 and a productivity of 72·4 wet g m^?2 d^?1 were recorded. Production of new fronds and loss of old fronds were determined at monthly intervals between April 1986 and March 1987. New frond production rates followed fluctuations in the quantity of light and varied between 0·08 and 0·48 fronds per plant per day. Frond loss rates did not show a seasonal pattern and fluctuated between 0·05 and 0·42 fronds per plant per day. It is suggested that the Falkland Islands Macrocystis population is more stable than most other giant kelp beds at high latitudes, because of the absence of winter storms.     

Microsite heterogeneity in litterfall risk to seedlings

Abstract Litterfall is an important cause of damage and mortality to seedlings in many forest ecosystems. This study is the first to investigate the contribution of variable risk of litterfall damage to microsite heterogeneity. Two hundred artificial seedlings were ‘planted’ in the ground at 2‐m intervals along transects in each of two New Zealand forests, and all plant species with foliage directly above each artificial seedling were recorded. Additional artificial seedlings were planted on the ground underneath treeferns and on their trunks (epiphytically). The artificial seedlings were monitored monthly for damage over 2 years. Three overtopping species that cause litterfall damage, along with one species that impedes litterfall, produced different microsites with a hierarchy of litterfall damage risk to seedlings (2–30% per year). This risk differed significantly among microsites (P < 0.0005). Seedlings differ in resilience to litterfall and, therefore, microsites with different litterfall risks provided the potential for regeneration niche differentiation. More seedlings were damaged beneath Cyathea dealbata (Cyatheaceae), which drops whole fronds, than on its trunks. The reverse was found for Dicksonia fibrosa (Dicksoniaceae), which retains dead fronds as a ‘skirt’. We suggest that shedding whole fronds, or producing a skirt of fronds, are alternative ‘strategies’ that can reduce competition from terrestrial and epiphytic seedlings, respectively.     

STRUCTURE AND DYNAMICS OF A POPULATION OF PALMARIA PALMATA (RHODOPHYTA) IN NORTHERN SPAIN1

Palmaria palmata (Linnaeus) O. Kuntze (Rhodophyta, Palmariaceae) is a seaweed commercially harvested for human consumption. Its population density, size structure, and frond dynamics were investigated from May 1999 to May 2001 at one intertidal locality in the northern coast of Spain, which is within the southern distributional boundary of the species in the eastern Atlantic coasts. The effect of size, age, and the life‐history phase (haploid vs. diploid) on frond growth and mortality were also evaluated. The study was carried out by mapping and monitoring fronds in the field. New fronds (macroscopic recruits or sprouts) appeared in spring, but subsequent mortality of these young fronds and detachment of the host plant led to lower density values in January. Palmaria palmata exhibited a distinctive seasonal growth cycle, with positive net growth from March to August and breakage from August to March. Interannual differences were also detected, with higher net growth in 2000 than in 1999. Net growth was apparently independent of age, reproductive status (fertile vs. reproductive), and life‐history phase (haploid vs. diploid) but was dependent on size, as longer fronds showed minor growth or greater breakage than small ones. Mortality, on the other hand, was more dependent on age than on size in the period analyzed (March–May 2000). Results of the study indicate that both size and age should be included as state variables and temporal changes in transition probabilities considered in the development of demographic models of the species.     

EFFECTS OF NITROGEN AND PHOSPHORUS LEVELS,AND FROND-HARVESTING ON ABSORPTION,TRANSLOCATION AND ACCUMULATION OF ARSENIC BY CHINESE BRAKE FERN (PTERIS VITTATA L.)

This hydroponic experiment was conducted to determine the effects of nitrogen (N) and phosphorus (P) levels and frond-harvesting on the effectiveness of arsenic (As)-hyperaccumulator Chinese brake fern (Pteris vittata L.) to remove As from contaminated groundwater collected from south Florida. Three-month old ferns were grown in 38-L plastic tanks (two ferns per tank) containing 30-L of As-contaminated water (130 μg·L^?1 As), which was amended with modified 0.25 strength Hoagland's solution #2. Two N (26 or 52 mg·L^?1) and two P levels (1.2 and 2.4 mg·L^?1) were tested in one experiment, whereas the effect of frond-harvesting was tested in a separate experiment. Initially, N had little effect on plant As removal whereas low P treatment was more effective than high P and As was reduced to <5 μg·L^?1 in 28 d compared to 35 d. For well-established ferns, N and P levels had little effect. Reused fern, with or without harvesting the As-rich fronds, took up arsenic more rapidly so the As concentration in the groundwater declined faster (130 to ～10 μg·L^?1 in 8 h). Regardless of the treatments, most As (85–93%) was located in the aboveground tissue (rhizomes and fronds). Frond As concentrations were higher for non-harvested ferns than for ferns where fronds were partially harvested prior to treatment. Conversely, rhizomes accumulated more arsenic in ferns where fronds had been partially harvested. Low-P treatment coupled with reuse of more established ferns with or without harvesting fronds can be used to effectively remove arsenic from contaminated water using P. vittata     

Charbeckia macrophylla gen. et sp. nov. from the Lower Mississippian Price (Pocono) Formation of southeastern West Virginia

A fossil plant discovery from the Price (Pocono) Formation of southeastern West Virginia provides new information on the poorly known compression floras of the Lower Mississippian of North America. The new plant described herein consists of long tapering bipinnate fronds with imbricate basal pinnae, planate apical pinnae, and unlobed, elliptical to obovate pinnules with open dichotomous venation. Veins concentrated in the medial region of the pinnule curve toward the lateral margin, suggestive of an early stage in the evolution of a midrib. Pinnules exhibit a distinctly revolute or otherwise reinforced margin. The exceptional length of some fronds (over 1m) and pinnule size (some over 3cm by 2cm) strongly contrast with the generally diffusely branched fronds and small or highly dissected pinnule morphology that typify Early Mississippian leaf taxa. A new generic assignment, Charbeckia macrophylla, is thereby justified. The rigid appearance of the tapering rachis, the imbricate pinnae that appear to have resisted compression, and the reinforced pinnule margins imply thick evergreen leaves, perhaps adapted for drought tolerance. A possible Calamopityalean affinity is indicated by the size of the fronds and the stout petioles, which fall within the expected size range of the Kalymma-type petiole bases described from the nearby New Albany Shale of Tournaisian age.     

The relationship between stand biomass and frond density in the clonal alga Mazzaella cornucopiae (Rhodophyta,Gigartinaceae)

The negative relationship between stand biomass and plant density observed in terrestrial plants was tested among fronds of a clonal red alga, Mazzaella cornucopiae. Stand biomass and frond density were estimated bimonthly for 1 year on 7 permanent quadrats. A positive linear correlation was found between biomass and density for the whole data set, suggesting the lack of self-thinning among fronds of this intertidal alga at natural densities. Higher frond densities could favor increased water retention among fronds, thus minimizing desiccation during low tides. In this way, stands could maintain higher production of biomass. Fronds may also be cushioned better against wave action at higher frond densities, thus decreasing the detachment of larger fronds. The temporal variation of the relationship between biomass and density was plotted separately for these 7 quadrats. Four quadrats showed positive linear correlation between both variables (the other three quadrats showed non-significant positive linear correlation). Their four slopes are statistically similar to that found for the entire data set. It is possible, then, that there is only one positive slope for the biomass-density relationship in this population. If this is true, standing biomass could be estimated from the density of fronds.     

Light-Induced Adaptive Responses under Greenhouse and Controlled Conditions in the Fern Pteris cretica var. ouvrardii

The influence of different growth irradiance conditions on plant development and foliar features were assessed in a shade-adapted fern variety, Pteris cretica var. ouvrardii. A comparison of frond morphology, anatomy, chloroplast infrastructure and chlorophyll content of plants cultivated in both greenhouse and in controlled growth chambers under moderate light, low light (control) and extreme shade revealed pronounced phenotypic modifications. Moderate light induced decreased frond surfaces, thicker leaves, lower chlorophyll content per surface unit, and a markedly reduced density of intraplastidial membranes. In contrast, morphological responses to extreme shade included the formation of larger, thinner fronds, increased chlorophyll content; and a higher membrane density in chrloplasts. A dorsi-ventral distribution of starch-gorged chlroplasts (lower mesophyll cell layers) and essentially starch-free chloroplasts (upper cell layer) characterizes low-light and moderate light fronds, while homogenous starch-free chloroplasts are present in all cell layers of extreme shade fronds. The light-induced modifications are discussed as adaptive responses.     

Studies on Gracilaria Sp.: Experiments on inocula incubated under greenhouse conditions

Field-collected plants of Gracilaria sp. and those from laboratory culture were grown in tanks with running sea water in a greenhouse. Difference in the rates of growth of field-collected plants from various sites were more noticeable during summer than during autumn. The size of fronds used as inocula had little effect on the increments of growth, while subapical segments quickly regenerated apices after which growth was comparable to apical segments. Tetrasporic fronds of field-collected plants increased somewhat more in weight than did gametophytic fronds as was the case with sporelings from laboratory culture; results were variable with mature fronds from laboratory culture. Male plants from laboratory culture showed somewhat better growth than did comparable female plants.     

Leaf development of the ostrich fern Matteuccia struthiopteris (L.) Todaro

The timing of emergence of the three different leaf types of Matteuccia struthiopteris is described from plants sampled over the course of a growing season. Vegetative leaves were first to appear, followed five weeks later by sporophylls and cataphylls. Leaf number and type, and total leaf dry weight per plant were assessed in weekly transects. Vegetative fronds contributed the most to total leaf dry weight, which increased during the first four weeks, and then remained constant for the remainder of the season. Cataphylls, although numerous by the end of the season, contributed little weight. Sporophylls occurred on the widest plants with the most vegetative leaves and greatest leaf weight, whereas cataphylls occurred on most plants except the smallest. Experimentally defoliated plants were re-examined in late summer. Following initial harvest, plants often produced a second smaller set of leaves. These were restricted to vegetative leaves and cataphylls. Ability to reissue leaves, especially vegetative fronds, declined very quickly after the first few weeks in the growing season. Defoliated plants draw on the extensive reservoir of developing leaves which are found on the rhizome, thus possibly diminishing the ability of the plant to withstand regular harvesting of the young fronds for food. Individual leaves were tagged and measured over the growing season. Non-linear regression curves fitted to the growth data for the three types of leaves indicate that growth was described best by a monomolecular growth curve for the vegetative and fertile fronds. Cataphyllar growth could be described equally well by either a monomolecular or a logistic function.     

Morphology and growth habit of Dicksonites pluckenetii from the Upper Carboniferous of Graissessac (France)

Morphological variability of the vegetative fronds of Dicksonites pluckenetii (SCHLOTHEIM ex STERNBERG) STERZEL is described from new material collected in the Stephanian Basin of Graissessac (Southern Massif Central France). Complete bipartite fronds sometimes still attached to their parent stem allow us to reconstruct the plant as a scrambler/climber. This interpretation is supported by the relatively small slender stems with long internodes and densely covered by short spines, which are also present along the entire length of petioles. A fertile pinna with slightly reduced pinnules bearing up to six radially symmetrical synangia is interpreted as a portion of male frond of the same species; its organization confirms the relationships of Dicksonites with the Callistophytales as was already suggested by features of the female fronds.     

Effects of arsenic species and concentrations on arsenic accumulation by different fern species in a hydroponic system

Two hydroponic experiments were conducted to evaluate factors affecting plant arsenic (As) hyperaccumulation. In the first experiment; two As hyperaccumulators (Pteris vittata and P. cretica mayii) were exposed to 1 and 10 mg L(-1) arsenite (AsIII) and monomethyl arsenic acid (MMA) for 4 wk. Total As concentrations in plants (fronds and roots) and solution were determined In the second experiment P. vittata and Nephrolepis exaltata (a non-As hyperaccumulator) were exposed to 5 mgL(-1) arsenate (AsV) and 20 mgL(-1) AsIIIfor 1 and 15 d. Total As and AsIII concentrations in plants were determined Compared to P. cretica mayii, P. vittata was more efficient in arsenic accumulation (1075-1666 vs. 249-627mg kg(-1) As in the fronds) partially because it is more efficient in As translocation. As translocation factor (As concentration ratio in fronds to roots) was 3.0-5.6 for P. vittata compared to 0.1 to 4.8 for P. cretica. Compared to N. exaltata, P. vittata was significantly more efficient in arsenic accumulation (38-542 vs. 4.8-71 mg kg(-1) As in thefronds) as well asAs translocation (1.3-5.6 vs. 0.2-0.5). In addition, P. vittata was much more efficient in As reduction from AsV to AsIII (83-84 vs. 13-24% AsIII in the fronds). Little As reduction occurred after 1-d exposure to AsV in both species indicates that As reduction was not instantaneous even in an As hyperaccumulator. Our data were consistent with the hypothesis that both As translocation and As reduction are important for plant As hyperaccumulation.