The period of active growth for spring ephemeral plants coincides with the period of high light, water and nutrient availability between snow melt and canopy closure in the understorey of deciduous forests in eastern North America. However, low temperatures prevail during this period and might restrict the performance of these plants. Remarkably, this peculiar phenology is extremely rare among annual plants. To understand better the role of light and water availability and of temperature in the phenology of spring ephemeral plants, we investigated the effects of two temperature regimes (low: 16/7 °C and high: 21/14 °C), three water availability levels (saturated, control and drought), and three photosynthetically active photon flux densities: low (85–100 μmol m−2 s−1); intermediate (182–196 μmol m−2 s−1); high (437–454 μmol m−2 s−1) on the growth and reproduction of the annual Floerkea proserpinacoides. Total biomass, total leaf area and flower and seed production increased with increasing temperature, water availability and light intensity. Total leaf area and total biomass were reduced in plants that were stressed under drought. However, at high temperatures, this reduction was less pronounced when droughted plants were partially shaded. At low temperatures, plants began to senesce after approximately 9 wk, whereas at higher temperatures, signs of senescence appeared after only 7 wk of growth. Despite shorter longevity, total biomass was approximately 1.5 times higher in the control water treatment at higher than at lower temperatures as a result of greater above-ground growth, and plants allocated a significantly greater proportion of mass gain to seed production. Although F. proserpinacoides can tolerate low temperatures such as those typical of early spring, higher temperatures such as those of late spring/early summer are more favorable for growth and reproduction as long as water and light are not limiting. Spring ephemeral annuals might be rare because low temperatures reduce growth rate and extend the life cycle. An annual plant might not have time to reproduce before resource availability deteriorates with canopy closure unless reproduction begins early in the life cycle of the species.

The flooding tolerance of Carex species was studied in relation to their field distribution and their capacity to form root aerenchyma under controlled conditions. In an alpine meadow, six Carex species were selected which were distributed in a clear zonation correlating with water content of the soil. Carex sempervirens and C. ferruginea were only found on nonflooded soil, the latter species preferring moister conditions. Carex davalliana and C. nigra were both associated with water-saturated soil, whereas C. limosa and C. rostrata preferred partially submerged conditions. Carex davalliana and C. limosa were bound to flooded soils with a relatively high redox potential and horizontally flowing groundwater. Carex rostrata and C. nigra grew in stagnant soil-flooded conditions with low soil redox potentials. The amount of aerenchyma in the roots of all species increased when grown in oxygen-deficient stagnant agar. This increase in root porosity, combined with increased root diameter, presumably improved internal aeration of the roots. Although all species survived experimental soil flooding, partial submergence was lethal to C. sempervirens and, surprisingly, also to the wetland species C. davalliana. Carex ferruginea showed a reduced growth rate during partial submergence. The three other species, all wetland plants, reached highest biomass production under soil-flooded and partially submerged conditions, with slower growth on free-draining soil. It is concluded that aerenchyma is not constitutive in the Carex species under study, and is best developed in Carex species from wetlands. Species with less aerenchyma perform poorly when soil-flooded, but conditions of partial submergence could even affect species with a considerable amount of root aerenchyma.

Spore capsules of four Sphagnum species were buried at different depths in peat on a bog. Spore viability was determined after 0, 1, 2 and 3 yr. Viability generally declined with time, but viable spores were still found at all depths after 3 yr. The light-coloured spores of S. balticum and S. tenellum retained their viability better than the darker spores of S. fuscum and S. lindbergii. Survival was highest under wet but aerobic conditions, but was also high under humid or periodically desiccated conditions. By contrast, most spores stored under wet, anaerobic conditions died within 2–3 yr. These results, and predictions from them, are not consistent with earlier results for spores of long-lived and dominant bryophytes, or for seeds of phanerogams of undisturbed wetlands and forests. There was no correlation between spore size and longevity across species, but the small spores from small capsules of S. balticum and S. tenellum generally showed higher viability than those from the medium-sized and large capsules of the same species. This suggests a positive intraspecific relationship between longevity and dispersal distance. There was an indication of conditional dormancy, controlled by weather, in Sphagnum spores. The experiments indicate that Sphagnum spores can form a long-term persistent spore bank under suitable conditions, with a half-life of between 1 and 20 yr (mean across species of 2.6 and 5.0 yr at two depths studied), and with potential values in individual spore capsules of several decades, or even of centuries. Sphagnum spores kept refrigerated showed 15–35% viable spores after 13 yr. The capacity to form a persistent spore bank that can be activated whenever favourable conditions occur might help explain the wide geographical distribution of many Sphagnum species in the boreal and temperate zones, where they have managed to colonize almost every suitable patch of acidic, nutrient-poor wetland.

The purpose of this study was to describe morph-specific patterns of stigma–anther separation and style curling in the distylous Jasminum fruticans. We also examined whether variation in floral traits is correlated with variation in seed production. Stigma–anther separation is more variable in short-styled plants than in long-styled plants. In all populations studied, some plants bear flowers that lack any stigma–anther separation. These plants have the pollen characteristics (size and number) and compatibility relations of short-styled plants. Comparison with other distylous species illustrates that the variability of stigma–anther separation in short-styled plants is a novel finding for a distylous species. Long-styled plants have greater stigma–anther separation than short-styled plants, styles are often curled and protrude from the corolla, and anthers are placed well within the corolla tube. The frequency of long-styled plants with curled styles and the mean degree of style curling were significantly correlated with style length. Short-styled plants have larger corollas than long-styled plants and never have curled styles. Morph ratios are always 50[ratio ]50 in natural populations. Mean values of each floral trait in the two morphs were significantly correlated among populations. There were no consistent differences in fecundity of the two morphs nor any correlation between floral traits and seed set for each morph in natural populations. We discuss the potential causes and significance of the two morph-specific patterns we describe; reduced stigma–anther separation in short-styled plants and the presence of curled styles in long-styled plants.

A lacustrine sequence from Lake Sedmo Rilsko (altitude 2095 m) in the northwest of Rila Mountain, Bulgaria, was analysed on the basis of 84 pollen spectra and three 14C accelerator mass spectrometry dates. The lower part of the sequence (413–530 cm) corresponds to the Late-glacial. Three phases, two stadial and one interstadial, are characterized by the dominance of mountain–steppe herb vegetation composed of Artemisia, Chenopodiaceae and Poaceae, with single trees of Pinus and shrub land of Juniperus and Ephedra. The identification of pollen grains of Abies, Quercus robur-type, Corylus, Acer, Fagus and other mesophilous trees suggests that they survived the harsh Late-glacial conditions in refuges below an altitude of 1000 m, where moisture was sufficient for their growth. In the early Holocene period, Betula forests at high altitudes and, below them, closed deciduous forests with Quercus, Tilia, Ulmus and Corylus, occurred from 11800 until approx. 6700 cal. BP. The formation of the coniferous belt dominated by Pinus sylvestris, Pinus peuce and Abies alba lasted from between 6700 and 5000 cal. BP. The forest dynamics in the Subboreal and the Subatlantic ended with the invasion of Fagus sylvatica and Picea abies after approx. 4500 and 3300 cal. BP, respectively. Indications of anthropogenic activities, expansion of agriculture in the lowland foothills, and livestock grazing in the mountain meadows and pastures, are clearly evident from the pollen diagram from 2400 cal. BP onwards.

The first known indicator of probable fern epiphytism in the Tertiary fossil record is documented from the Eocene London Clay of southeast England. This pyritised fern rachis exhibits major deviation from the basic form of petiolar vascular trace morphology shown by the other London Clay fossil ferns and is here attributed to the Polypodiaceae. This represents the first known occurrence of this family in the London Clay macroflora, and brings the total of distinct fern rachis types from the Lower Tertiary of southeast England to six. The significance of this find is interpreted in relation to its probable origins from a tropical rainforest palaeoflora in which it is proposed that this specimen represents the first occurrence of an epiphytic component.

Using the outcrossing Primula farinosa and its autogamous selfing relatives P. scotica, P. scandinavica and P. stricta, we compared the fitness of light and heavy seeds. Heavy seeds germinated in greater numbers and more quickly. In competition with seedlings grown from lighter seeds, heavy seeds produced larger rosettes. In P. farinosa such seedlings went on to produce more seeds, and in two populations heavier seeds, than plants from lighter seeds. After transplantation to natural populations, seedlings of P. farinosa derived from heavy seeds produced larger rosettes, more flowers and seeds than those from lighter seeds in certain populations so that seedlings born of heavy seeds were much fitter than seedlings from lighter seeds. Average seed weight varied in inverse proportion to seed number per capsule. The autogamous species produced on average about twice as many seeds per capsule as P. farinosa. In P. scotica and P. stricta this difference appears to be due in part to assured fertilization, but this high fecundity did not cause disadvantageously light seeds. As these species produced fewer capsules per scape, their overall seed production was on average no greater than for P. farinosa. P. farinosa traded-off fitness between capsules with large seed numbers, which donated more offspring to the next generation, and those with small seed numbers, whose heavy seeds would be more likely to reproduce themselves in the next generation. We conclude that low fecundity in outcrossing species might at times be advantageous.

A lectin with hemagglutinating activity has been isolated from an aqueous extract of the symbiotic phenotype of Dictyonema glabratum and its cyanobacterial photobiont Scytonema sp. The purified lectin had a pI of 6.8 and its molecular mass was investigated by electrospray ionization mass spectrometry, gel filtration and SDS-PAGE, which indicated its native conformation as a dimer formed by two identical subunits of 16540 Da. The lectin is a glycoprotein with a low degree of glycosylation, containing galactose, xylose, glucose and mannose as neutral monosaccharides, in addition to glucosamine, which could indicate both N- and O-linkages. Amino acid analysis showed the predominance of nonpolar residues such as phenylalanine. Agglutination of human erythrocytes required divalent cations, which is affected by addition of EDTA. The lectin was more stable at 30 °C or less for at least 1 h and between pH 5.0 and 7.0. Among the various compounds tested for hemagglutination inhibition, N-acetylgalactosamine was the most active. The potential role of this lectin in recognition of the compatible cyanobacterial photobiont is discussed.

Experiments were set up to assess the relative impacts of grass lamina fragment density, size and quality on the activity and growth of four fungi in a particulate soil-like matrix. The fungi studied were Cladosporium cladosporioides, Fusarium lateritium, Phoma exigua and Trichoderma viride, all of which are common inhabitants of UK upland grassland soils. Resource quality was varied by using three contrasting grasses as sources of lamina fragments: Lolium perenne, Agrostis capillaris and Nardus stricta. All the fungi were able to forage effectively through the soil-like matrix (at a rate of 1–2 ml matrix d−1) and colonize and partially decompose available lamina fragments (up to 40% d. wt loss). Foraging rates (ml matrix d−1) were affected by lamina fragment species but not by fragment density or size. In general, F. lateritium and T. viride foraged at a faster rate than the other species. Mycelial activity in the soil-like matrix was directly proportional to total lamina fragment availability and was unaffected by fragment size. Biomass production on solid media was also directly related to substrate (carbohydrate) availability. The results indicate that these fungi can adjust their growth patterns in response to fragment density so as to maximize foraging efficiency (energy acquired per unit exploratory biomass production). Differences in lamina fragment species were responsible for up to 50% reduction in mycelial activity.

Sarcodes sanguinea and Pterospora andromedea (Ericaceae, Monotropoideae) are nonphotosynthetic myco-heterotrophic plants. Recent studies have shown that the roots of the adult plants are always associated with closely related but exclusive sets of Rhizopogon species (Basidiomycota, Boletales) from section Amylopogon. We have isolated Rhizopogon species that were associated with the adult plants and used them to germinate seeds under gnotobiotic conditions. All Rhizopogon species isolated from either plant species were capable of stimulating seed germination in both Sarcodes and Pterospora. Under the primary conditions used, germination varied from 9 to 73% in the case of Sarcodes and 0 to 13% in that of Pterospora. The single Rhizopogon strain that failed to elicit germination in Pterospora under these conditions did stimulate germination under slightly different conditions. By contrast, seeds failed to germinate on all media which lacked these Rhizopogon species, or in the presence of six other genera of basidiomycetes. Seed germination could be stimulated either through cellophane or at the edge of fungal colonies without direct fungus–seed contact. These results suggest that a diffusible or volatile compound that is unique to Rhizopogon stimulates germination of these plant seeds. Seed lots of Sarcodes from two successive years had similar germination levels. Sarcodes seeds that had overwintered under natural conditions were also stimulated to germinate. These results demonstrate the potential for long-term dormancy. We suggest that a combination of dormancy and the use of specific germination cues might increase the opportunities of these plants for recruitment. In addition, the specific germination response explains at least a part of the specialized associations observed in the adult plants. Nevertheless, the seeds respond to a slightly broader range of Rhizopogon species than has been observed to be associated with the adult plants; thus other factors must also be involved with specificity under natural conditions.

A total of 107 putative ericoid mycorrhizal endophytes were isolated from hair roots of Calluna vulgaris from two abandoned arsenic/copper mine sites and a natural heathland site in southwest England. The endophytes were initially grouped as 14 RFLP types, based on the results of ITS-RFLP analysis using the restriction endonucleases Hinf I, Rsa I and Hae III. ITS sequences were obtained for representative isolates from each RFLP type and compared phylogenetically with sequences for known ericoid mycorrhizal endophytes and selected ascomycetes. The majority of endophyte isolates (62–92%) from each site were identified as Hymenoscyphus ericae, but a number of other less common mycorrhizal RFLP types were also identified, all of which appear to have strong affinities with the order Leotiales. None of the less common RFLP types was isolated from C. vulgaris at more than one field site. Neighbour-joining analysis indicated similarities between the endophytes from C. vulgaris and mycorrhizal endophytes isolated from other Ericaceae and Epacridaceae hosts in North America and Australia.

Some mycorrhizal plants exhibit greater resistance than nonmycorrhizal plants to aluminium toxicity. This has not yet been shown for banana despite its importance as a cash and food crop in tropical regions, although bananas are sensitive to aluminium stress. We studied the effects of the arbuscular mycorrhizal fungus Glomus intraradices in alleviating aluminium toxicity in the banana cultivar Grande Naine grown in a continuous-nutrient-flow cultivation system using dilute solution. The micropropagated plants, some of which were inoculated with arbuscular mycorrhizal fungus, were grown for 40 d in pots filled with sand, and continuously irrigated with a nutrient solution containing up to 180 μM of aluminium. Water and nutrient uptake were measured once a week for 24 h, and root arbuscular mycorrhizal fungal colonization, biomass production, and mineral content of roots and shoots were measured at harvest. The root arbuscular mycorrhizal fungal colonization was large, and not significantly influenced by aluminium treatment. The effects of aluminium on both mycorrhizal and nonmycorrhizal plants were: decrease in biomass production, water and nutrient uptake, and magnesium content of roots and shoots; greater aluminium content in roots than in shoots; and increase in potassium and phosphorus content, particularly in roots. A significant positive effect of arbuscular mycorrhizal fungi on plant growth was observed with aluminium treatment, and was most pronounced at the highest concentration. The benefits, compared with nonmycorrhizal plants, included: increase in shoot dry weight, uptake of water and of most nutrients, and in calcium, magnesium and phosphorus content, particularly in roots; decrease in aluminium content in root and shoot; and delay in the appearance of aluminium-induced leaf symptoms. These results indicate that arbuscular mycorrhizal fungi could be effective in alleviating aluminium toxicity to banana plants.

Two mycotrophic species (Lactuca sativa and Abutilon theophrasti) and one nonmycotrophic species (Beta vulgaris) were grown in a P-deficient soil, and the effects of mycorrhizal inoculation on three variables that determine growth rate were assessed for each. The phosphorus-use efficiency (PUE, dW/dP) is the ratio of d. wt increase to P content increase. Plant P is the amount of P (the limiting resource) controlled by the plant, which can be allocated to various purposes. The phosphorus efficiency index (PEI, dP/Pdt) is the efficiency with which plant P is used to acquire P from the soil. Inoculated and control plants of a given species initially contained the same amount of P because all plants were grown from seed. Mycorrhizal colonization significantly increased the PEI of Lactuca and Abutilon (by 23 and 32%, respectively). As expected, mycorrhizal inoculation did not significantly increase the PEI of Beta. As a result, mycorrhizal inoculation significantly increased the P content of Lactuca and Abutilon, but not Beta. Mycorrhizal colonization decreased the PUE of lettuce, but did not significantly affect that of Abutilon or Beta. Mycorrhizal inoculation therefore slightly increased the growth rate of Lactuca, greatly increased the growth rate of Abutilon, and ultimately had no significant effect on the growth rate of Beta.

A study was conducted to quantify the ability of entrapped, monoxenically produced spores of an arbuscular mycorrhizal fungus to germinate and reproduce the fungal life cycle after cryopreservation. No germination was obtained after incubation of entrapped spores in glycerol and mannitol and subsequent cryopreservation at −70 °C, regardless of the concentration of cryoprotectants and duration of incubation. Incubation for 1 d in 0.5 M sucrose, and for 1 and 2 d in 0.5 M trehalose, led to spore germination after cryopreservation at −70 °C. Lower cryopreservation temperatures were tested with entrapped spores incubated for 1 d in 0.5 M trehalose. The highest germination rate, estimated by the percentage of potentially infective beads (%PIB), was obtained at −100 °C. A %PIB of 95% (water agar medium) to 100% (Strullu–Romand medium) was obtained at this temperature. Thereafter, %PIB rapidly decreased at −140 and −180 °C. Heavy sporulation and high internal root colonization were obtained after re-association of the entrapped spores, incubated for 1 d in 0.5 M trehalose and subsequently cryopreserved at −100 °C, with transformed carrot roots. This demonstrates the ability of entrapped spores to reproduce the fungal life cycle following cold treatment.

The effect of colonization of tissue-cultured strawberry (Fragaria × ananassa Duch. cv. Kent) plantlets in vitro by the arbuscular mycorrhizal fungus (AMF) Glomus intraradices on plantlet response to poly(ethylene glycol) (PEG)-8000-induced water stress was investigated. The plantlets were inoculated axenically and co-cultured with the AMF for 4 wk, then transferred to 15% PEG-8000 solutions for 4, 8 and 12 h. Relative water content, water potential, osmotic potential, leaf conductance for water vapour diffusion and photosynthetic efficiency as estimated by chlorophyll a fluorescence were all affected by the PEG treatment and its duration but not by the presence of the intraradical phase of the AMF. However, distinct differences in PEG-induced changes in amino acid content were observed between nonmycorrhizal and mycorrhizal plantlets. In the latter, the treatment with PEG caused a substantial decrease in asparagine levels in leaves that was accompanied by a marked increase in asparagine concentration in roots. The opposite was observed in nonmycorrhizal plantlets. Furthermore, concentrations of aspartic acid, serine, threonine, amino-N-butyric acid, alanine and starch increased in roots of mycorrhizal and decreased in nonmycorrhizal plantlets. Our results suggest the presence of a mobile pool of asparagine that can be translocated from leaves to roots or vice versa in response to PEG-induced water stress, depending on the mycorrhizal status of the plantlets. These opposite patterns suggest different strategies of mycorrhizal and nonmycorrhizal plantlets to water stress, which seem to involve different adjustments in nitrogen and carbon metabolism.