Survival Of Sporophytes Research Articles

Effects of temperature and nutrients on microscopic stages of the bull kelp (Nereocystis luetkeana, Phaeophyceae).

Warming ocean temperatures have been linked to kelp forest declines worldwide, and elevated temperatures can act synergistically with other local stressors to exacerbate kelp loss. The bull kelp Nereocystis luetkeana is the primary canopy-forming kelp species in the Salish Sea, where it is declining in areas with elevated summer water temperatures and low nutrient concentrations. To determine the interactive effects of these two stressors on microscopic stages of N. luetkeana, we cultured gametophytes and microscopic sporophytes from seven different Salish Sea populations across seven different temperatures (10-22°C) and two nitrogen concentrations. The thermal tolerance of microscopic gametophytes and sporophytes was similar across populations, and high temperatures were more stressful than low nitrogen levels. Additional nitrogen did not improve gametophyte or sporophyte survival at high temperatures. Gametophyte densities were highest between 10 and 16°C and declined sharply at 18°C, and temperatures of 20 and 22°C were lethal. The window for successful sporophyte production was narrower, peaking at 10-14°C. Across all populations, the warmest temperature at which sporophytes were produced was 16 or 18°C, but sporophyte densities were 78% lower at 16°C and 95% lower at 18°C compared to cooler temperatures. In the field, bottom temperatures revealed that the thermal limits of gametophyte growth (18°C) and sporophyte production (16-18°C) were reached during the summer at multiple sites. Prolonged exposure of bull kelp gametophytes to temperatures of 16°C and above could limit reproduction, and therefore recruitment, of adult kelp sporophytes.

Development and survival of Buxbaumia viridis (Moug. ex DC.) Brid. ex Moug. & Nestl. sporophytes in Hungary

ABSTRACT Introduction Buxbaumia viridis is a rare but well-researched bryophyte in Europe. Owing to its small size and unusual life cycle, its developmental stage is key for its detection in the field, so it is surprising that intensive field research on its phenology has not previously been carried out. Methods During a systematic study from 2014 to 2020, data from extensive (space-for-time) and intensive surveys were collected on the development of Buxbaumia viridis sporophytes in Hungary. Damage to sporophytes and sporophyte survival rate were also examined. Key results Twelve developmental stages were distinguished and characterised in this study. Juvenile sporophytes started to grow in autumn, and about half of the sporophytes died before their maturation in summer. Asexual propagules (gemmae) were produced all year round. Conclusions Precise description of the developmental characteristics helps distinguish Buxbaumia viridis from B. aphylla, even at juvenile stages in autumn; however, early spring was found to be the best period for field surveys. The observed mortality rate is probably a species-specific constant, so (on its own) may not pose a threat to the survival of populations. Large numbers of gemmae probably increase the likelihood of local survival.

Low-Trunk Epiphytic Fern Gametophyte and Sporophyte Occurrence Is Influenced by Moss Height and Density in a Costa Rican Lowland Tropical Rain Forest

Premise of research. Tropical epiphytic ferns and mosses commonly inhabit similar niche spaces, yet little is known about the interspecific interactions between the two, especially with reference to the fern life cycle of functionally distinct, independent gametophytes and sporophytes. Previous research has shown that mosses often act as ecosystem engineers, storing water and altering the microclimate to allow seed plant establishment. And because ferns require free water for gamete exchange, mosses may play an important facilitative role in fern fertilization. In our study, we examine the spatial relationships between low-trunk epiphytic mosses, fern gametophytes, and sporophytes in a lowland tropical rain forest in Costa Rica.Methodology. We surveyed low-trunk (0–2 m above the forest floor) epiphytic ferns at La Selva Biological Station and compared the height (average of five tallest ramets) and density (classified into four classes based on percentage of cover) of mosses near fern gametophytes and fern sporophytes while considering the effects of other abiotic factors including light, azimuth, height on the tree, and tree diameter at breast height.Pivotal results. A logistic regression analysis of fern life stage against all measured abiotic and biotic factors revealed that only moss height predicted the occurrence of fern gametophytes or sporophytes. Fern gametophytes occurred in shorter moss, while fern sporophytes occurred in taller moss. As moss density increased, the percentage of sporophyte individuals increased, while the percentage of gametophytes decreased.Conclusions. Our data show evidence of a novel biotic mechanism that assists the success of ferns as epiphytes. The results indicate that tall moss, possibly through microclimatic properties, facilitates gametophyte fertilization or sporophyte survival but outcompetes fern gametophytes as the moss increases in height and density. Unraveling the interspecific interactions between these two dominant epiphyte lineages provides further insight into canopy successional processes, biotic interactions among epiphytes, and fern community ecology.

Daylength influences reproductive success and sporophyte growth in the Arctic kelp species Alaria esculenta

Many organisms have endogenous clocks that synchronize biological processes with environmental changes, leading to optimized development and reproduction. However, certain environments, like the Arctic, pose a special challenge to circadian clocks, particularly due to extreme seasonal changes in daylength, ranging from permanent sunlight to complete darkness. Kelps seem to be well adapted to the variable environmental conditions characteristic of this region. However, daylength might affect kelp species that use circadian rhythms to control the timing of daily egg release from female gametophytes. We aimed to investigate how daylength and light intensity affect gametogenesis and reproductive success of summer-reproducing kelp species (using Alaria esculenta as a model). As daylength and temperature co-vary most of the year, we also investigated the thermal resilience of the sporophytes developed under different daylengths to understand if there is a cross-tolerance between light doses and temperature tolerance. Although continuous daylight, characteristic of Arctic summers, enhanced gametogenesis and increased gametophyte vegetative growth, and thereby the number of potential reproductive gametophyte cells, sporophyte production was higher under long (16 h light:8 h dark) and intermediate (12:12 h) days. Sporophyte growth was triggered by changing daylength from short to long days, suggesting a synchronization with annual daylength variation. High daily light doses during reproduction and early development improved subsequent sporophyte survival at high (sub)lethal temperatures, indicating cross-tolerance between light and temperature. Reproductive success in Arctic A. esculenta was hampered under continuous light, and we hypothesize that this might result from disturbance of synchronized egg release and subsequent fertilization.

Phenology and survival of sporophytes in Dutch populations of Buxbaumia aphylla

Two Dutch populations of Buxbaumia aphylla (Nunspeet and Elspeet) were studied for two generations (2014–2015 and 2015–2016). At both sites the number and developmental stages of sporophytes were frequently recorded and sporophyte maturity indices and survival rates were determined. The timing of sporophyte development was similar between the two generations but differed between the growth sites with earlier sporophyte development at Nunspeet. The growth sites are located close to each other and share the same climate and soil characteristics. The growth site at Nunspeet, however, is shaded and consequently a higher soil moisture early in the season might explain early sporophyte development. Sporophyte survival was extremely low, especially at Nunspeet (0.4% and 0.9% in 2014–2015 and 2015–2016 respectively) due to fungi and, possibly, slugs and birds.

Elevated pCO2 is less detrimental than increased temperature to early development of the giant kelp, Macrocystis pyrifera (Phaeophyceae, Laminariales)

:Global climate change is increasing ocean temperature and partial pressure of CO2 (pCO2) in coastal and marine ecosystems. Research in this field has largely focused on how limited CO32− availability and low pH adversely affect early development of calcifying organisms, but noncalcareous organisms are comparatively understudied despite their prevalence in many coastal communities. We investigated how present-day and future levels of ocean temperature (12°C vs 15°C, respectively) and pCO2 (400 μatm vs 1500 μatm, respectively) influence successful germling production, gametophyte survival, growth, and sex ratio, and embryonic sporophyte production and growth in the habitat-forming kelp Macrocystis pyrifera over a 15-wk period in San Diego, California, USA. Our results indicate that relative to present-day conditions, successful germling production was reduced fourfold under elevated temperature alone, and fivefold under combined elevated temperature and pCO2 (i.e. “future conditions”). Similarly, survival and growth of male and female gametophytes were lower under elevated temperature alone than under either present-day, elevated pCO2 alone, or future conditions. Gametophyte sex ratios skewed slightly toward males across all treatments. Sporophyte recruitment and growth were greatest and occurred earliest under elevated pCO2 alone, but were delayed under elevated temperature alone. Although elevated pCO2 and temperature adversely affected germling production independently and cumulatively, elevated pCO2 enhanced gametophyte and sporophyte survival under both present-day and elevated temperatures. Thus, under projected climate change conditions, elevated pCO2 may be less detrimental than increased temperature for development beyond germling production. Given that M. pyrifera is globally distributed and provides numerous ecosystem services including the potential to mitigate ocean acidification, impacts of climate change on its complex life history merit further exploration.

Interactive effects of nutrient availability and temperature on growth and survival of different size classes of Saccharina japonica (Laminariales, Phaeophyceae)

:In northern Japan, the production of Saccharina japonica exhibits marked annual fluctuation due to changes in seawater temperature and nutrient availability during winter and spring. To better understand this phenomenon, we examined the combined effects of temperature (5°C, 10°C, 15°C and 20°C) and nutrient availability (seawater enriched with 25% Provasoli's enriched seawater vs nonenriched seawater) on photosynthesis, growth and survival and nitrogen and chlorophyll a contents of juvenile sporophytes (2–3 cm) and larger size class sporophytes (100–150 cm) from southern Hokkaido. Both juvenile sporophytes and discs from 100–150-cm-class sporophytes cultured in enriched seawater showed significantly higher growth rates and photosynthetic activities than those cultured in nonenriched seawater. This difference likely was due to the significantly higher nitrogen and chlorophyll a contents of thalli grown in enriched seawater. Significant effects of temperature on growth and photosynthesis were also detected. A significant interaction between temperature and nutrient availability for relative growth rate (RGR) was detected. The positive effect of elevated nutrient availability on RGRs was magnified by an increase in temperature from 5°C to 15°C for juvenile sporophytes and from 5°C to 10°C for 100–150-cm-class sporophytes; whereas, the negative effect of elevated temperature from 10°C to 15°C on RGRs of 100–150-cm-class sporophytes was antagonised by a reduction in nutrient availability. In contrast to the 100% survival rate in enriched seawater, dead juvenile sporophytes and discs from 100–150-cm-class sporophytes were found at 15°C and 20°C in nonenriched seawater, and the survival rates decreased with increasing temperature. Therefore, the growth and survival of sporophytes of S. japonica are significantly affected by nutrient availability and temperature, which may lead to marked fluctuations in annual production.

Effects of competition, shade and soil conditions on the recolonization of three forest herbs in tree‐planted riparian zones

AbstractQuestionsIn mesic forests, ecological filters due to past agricultural land use reduce forest herb recolonization. Is the recruitment of such species also limited in tree‐planted riparian zones by local filters such as competition, shade level and soil conditions?LocationTwo agricultural watersheds, southeastern Québec, Canada.MethodsThree herbs characteristic of natural riparian forests were selected for this study: one graminoid, Glyceria striata, and two ferns, Matteuccia struthiopteris and Onoclea sensibilis. Effects of shade level (75% vs 50%) and soil type (forest vs agricultural soil) on seedling emergence were evaluated in a seed‐sowing greenhouse experiment. In a 2‐yr transplant field experiment, seedling and sporophyte establishment was monitored in five natural riparian forests and five tree‐planted post‐agricultural riparian zones on microsites with understorey vegetation kept intact or cleared and on forest or agricultural soils. Using a priori contrasts, we assessed the influence of habitat type (natural riparian forests or tree‐planted riparian zones), competition and post‐agricultural soil type on transplant survival and growth.ResultsSeedling emergence tended to be higher on forest soils for G. striata while sporophyte emergence increased under 75% shade for M. struthiopteris. Transplanted seedlings and sporophytes of the three species survived and grew as well in tree‐planted riparian zones as in natural riparian forests. In tree‐planted riparian zones however, competing understorey vegetation reduced the survival and growth of G. striata and agricultural soil reduced the growth of M. struthiopteris. For O. sensibilis, only sporophyte survival was reduced by competition in tree‐planted riparian zones.ConclusionsPlanting trees in post‐agricultural riparian zones fosters establishment of forest herbs similar than those observed in natural riparian forests. Additional environmental filters specific to tree‐planted riparian zones, however, offset the positive influence of trees and limit recolonization of the three studied species. Considering the partial restoration success of establishment niches by tree planting, controlling spontaneous vegetation after tree planting is advised when conceivable and cost‐effective to promote the recolonization of environmentally‐limited forest herbs. Long‐term transplant experiments should be more often conducted to identify the ecological filters that reduce plant recolonization, and thereby design the most effective restoration strategies.

Comparative Cuticle Development Reveals Taller Sporophytes Are Covered by Thicker Calyptra Cuticles in Mosses.

The calyptra is a maternal structure that protects the sporophyte offspring from dehydration, and positively impacts sporophyte survival and fitness in mosses. We explore the relationship between cuticle protection and sporophyte height as a proxy for dehydration stress in Funariaceae species with sporophytes across a range of sizes. Calyptrae and sporophytes from four species were collected from laboratory-grown populations at two developmental stages. Tissues were embedded, sectioned, and examined using transmission electron microscopy. Cuticle thickness was measured from three epidermal cells per organ for each individual and compared statistically. All four species have cuticles consisting of a cuticle proper and a cuticular layer on the calyptra and sporophyte at both developmental stages. Across species, shorter sporophytes are associated with smaller calyptra and thinner calyptra cuticles, whereas taller sporophytes are associated with larger calyptra and thicker calyptra cuticles. Independent of size, young sporophytes have a thin cuticle that thickens later during development, while calyptrae have a mature cuticle produced early during development that persists throughout development. This study adds to our knowledge of maternal effects influencing offspring survival in plants. Released from the pressures to invest in protection for their sporophyte offspring, maternal resources can be allocated to other processes that support sporophyte reproductive success. Using a comparative developmental framework enables us to broaden our understanding of cuticle development across species and provides structural evidence supporting the waterproofing role of the moss calyptra.

Propagation and Cryopreservation ofAsplenium scolopendriumvar.americanum,the American Hart’s-Tongue Fern

Abstract Asplenium scolopendrium var. americanum is a federally-listed fern species that is found in several northern populations in the U.S. and Canada, as well as in three isolated locations in the southern U.S. In vitro methods were applied to the germination, propagation, and cryopreservation of this species. Germination of spores was obtained both in vitro and on soil, but the production of sporophytes from gametophytes did not begin until over two years after the spores were sown. In vitro cultures of both sporophytes and gametophytes were established, but sporophyte production from gametophytes has thus far only been observed on soil. Both in vitro-grown gametophytes and sporophytes survived cryopreservation using the encapsulation-dehydration procedure. Preculture on ABA-containing medium increased survival of sporophytes after cryopreservation, but good survival of gametophytes was observed with or without ABA. The use of Green Globular Body-like sporophyte tissue demonstrates the use of this tis...

Dehydration protection provided by a maternal cuticle improves offspring fitness in the moss Funaria hygrometrica

In bryophytes the sporophyte offspring are in contact with, nourished from, and partially surrounded by the maternal gametophyte throughout their lifespan. During early development, the moss sporophyte is covered by the calyptra, a cap of maternal gametophyte tissue that has a multilayered cuticle. In this study the effects on sporophyte offspring fitness of removing the maternal calyptra cuticle, in combination with dehydration stress, is experimentally determined. Using the moss Funaria hygrometrica, calyptra cuticle waxes were removed by chemical extraction and individuals were exposed to a short-term dehydration event. Sporophytes were returned to high humidity to complete development and then aspects of sporophyte survival, development, functional morphology, and reproductive output were measured. It was found that removal of calyptra cuticle under low humidity results in significant negative impacts to moss sporophyte fitness, resulting in decreased survival, increased tissue damage, incomplete sporophyte development, more peristome malformations, and decreased reproductive output. This study represents the strongest evidence to date that the structure of the calyptra cuticle functions in dehydration protection of the immature moss sporophyte. The investment in a maternal calyptra with a multilayered cuticle increases offspring fitness and provides a functional explanation for calyptra retention across mosses. The moss calyptra may represent the earliest occurance of maternal protection via structural provisioning of a cuticle in green plants.

Interactions between thermal and wave environments mediate intracellular acidity (H2SO4), growth, and mortality in the annual brown seaweed Desmarestia viridis

We used three laboratory experiments as well as measurements, throughout an entire growth season, of the length and survival of sporophytes, sea temperature, and wave height at two subtidal sites in Newfoundland (Canada), to investigate causal relationships between environmental variability, intracellular acidity, growth, and mortality in the highly acidic (H2SO4), annual brown seaweed Desmarestia viridis (O.F. Müller) J.V. Lamouroux. Light, grazing, and epibionts did not affect acidity. In the absence of waves, acid loss was threefold lower in cold (6.5°C) than warm (11°C) water, and threefold higher in the absence than presence of waves in warm (11 to 13°C) water. There were three phases of change in frond length at both sites: (1) increase [March to late June], (2) no change [July to mid-August], and (3) decrease [mid-August to late October]. Mortality rates and sea temperature in Phase 1 were low, whereas the onset of increasing mortality at the end of Phase 2 coincided well with the end of a 2-week period during which temperature increased rapidly, from 6 to 11°C. Results strongly suggested the more severe wave climate at the most wave-exposed site in September, when temperature was ~10°C, facilitated the dispersal of the acid being released, which delayed mortality by ~10days compared to the other site. All sporophytes had disappeared at both sites in late October. This is the first integrated analysis of seasonal variation in growth and mortality of D. viridis sporophytes. The strong connections between laboratory and field data attest to the critical role that thermal and hydrodynamic environments play in the life history of this unique seaweed.

Narrow Substrate Niche of Cheilanthes lanosa, the Hairy Lip Fern, is Determined by Carbohydrate and Lipid Contents in Gametophytes

Abstract Cheilanthes lanosa is a xerophytic fern that inhabits rock cliffs and crevices. Morphological features such as cuticle and trichomes assist sporophyte survival. However, the gametophyte stage appears to lack any water-saving features. Previous studies suggest that the gametophyte may balance its water through carbohydrate production and a strong internal osmotic gradient. To investigate the basis for gametophyte survival, lipids and carbohydrates were quantified using the vanillin and anthrone assays. Results suggest that lipids and carbohydrates increase in percent of total biomass (w/w) throughout development. In addition, lipid and carbohydrate content can change with varying culture conditions. Young gametophytes, with high carbohydrate and low lipid content, are relegated to substrates with a potential for a small but continuous water source.

Eisenia bicyclis bed coverage off Oshika Peninsula, Japan, in relation to sporophyte survival and Strongylocentrotus nudus abundance

It has recently been reported that the Eisenia bicyclis beds on the coast of Tomarihama in the Oshika Peninsula in Miyagi Prefecture (northern part of Japan) have been progressively receding from the offshore side of the beds every year. In this study, to determine the factors causing the change in the distribution of E. bicyclis beds as well as the extent of the change, an ecological survey of E. bicyclis and grazing animals was conducted. A 150 m-long fixed line was set up in the rocky coastal area on the Oshika Peninsula in Miyagi Prefecture, and the number of E. bicyclis individuals inhabiting a 1-m width was then measured. In addition, the numbers of individuals of sea urchins (Strongylocentrotus nudus) and abalone (Haliotis discus hannai) were measured. Although the E. bicyclis bed extended to the 64-m point on the fixed line at the time of the survey in August 1999, by July 2001, its lower limit was at the 53-m point; thus, a retreat of the outer edge of the bed of 11 m was observed in 2 years. The density of adult E. bicyclis sporophytes in the bed was reduced from 1.08 to 1.80 individuals (ind.) m−2, respectively. Juvenile sporophytes were also observed, but most of those that had settled near the lower limit of the bed failed to survive to become adult sporophytes. There were few sea urchins, the main grazing animal on the site, inside the E. bicyclis bed (3.5 ind. m−2 in October 2001) while there were many near the bed lower limit and on the deep-site side (12.9 ind. m−2 in October 2001). These results indicate that the high grazing pressure of sea urchins reduced the survival of juvenile sporophytes near the bed lower limit, thus impeding the recruitment of juvenile sporophytes to replace adult sporophytes that died due to senescence, storm action and/or grazing.

Tree Ferns in the Interior and at the Edge of a Mexican Cloud Forest Remnant: Spore Germination and Sporophyte Survival and Establishment1

The three most common tree fern species in a Mexican montane cloud forest fragment (Alsophila firma, Lophosoria quadripinnata and Sphaeropteris horrida) were selected for laboratory and transplant experiments. The objectives were: (1) to determine the percentage of spore germination and gametophytes producing sporophytes, and (2) to compare early establishment of sporophytes at the edge and in the interior of the forest. Percent spore germination varied between 16 and 86 percent, and the number of gametophytes that produced sporophytes was high (>50%). Survival and growth of sporophytes differed between species and habitats. Survival was greater at the edge than in the forest interior for Lophosoria, but it was similar for Alsophila and Sphaeropteris. Number and length of fronds were higher at the forest edge for individuals of Alsophila and Lophosoria, but not for Sphaeropteris. RGR was higher at the forest edge than in the forest interior for sporophytes of the three species. This study suggests that the forest edge is an appropriate habitat for establishment of Alsophila and Lophosoria, but Sphaeropteris is apparently a forest interior species. RESUMEN Las tres especies de helechos arborescentes mas comunes en un fragmento de bosque mesofilo de montana en Mexico (Alsophila firma, Lophosoria quadripinnata y Sphaeropteris horrida) se seleccionaron para llevar a cabo estudios en laboratorio y en el bosque. Los objetivos fueron: (1) determinar el porcentaje de germinacion de esporas y de game-tofitos que producen esporofkos y (2) comparar el establecimiento temprano de los esporofitos en el interior y en el horde del bosque. El porcentaje de germinacion de esporas vario entre 16 y 86 porciento, y el numero de gametofitos que produjeron esporofitos fue alto (>50%). La sobrevivencia y crecimiento de los esporofitos fue diferente entre especies y habitats. La sobrevivencia fue mayor en el borde que en el interior del bosque para Lophosoria, pero fue similar para los individuos de Alsophila y Sphaeropteris. El numero y la longitud de las frondas fue mayor en el horde del bosque para individuos de Alsophila y Lophosoria, pero no para Sphaeropteris. La tasa de crecimiento relativo fue mayor en el horde que en el interior del bosque para los esporofitos de las tres especies estudiadas. Los resultados sugieren que el borde es un habitat apropiado para el establecimiento de Alsophila y Lophosoria, pero que Sphaeropteris es, aparentemente, una especie de interior de bosque.

Tree Ferns in the Interior and at the Edge of a Mexican Cloud Forest Remnant: Spore Germination and Sporophyte Survival and Establishment

Tree Ferns in the Interior and at the Edge of a Mexican Cloud Forest Remnant: Spore Germination and Sporophyte Survival and Establishment

Comparative Habitat Requirements for Spore Germination and Prothallial Growth of Three Ferns in Southeastern Michigan

Investigation of the physiological ecology of various plants has yielded information concerning mechanisms and patterns of evolutionary divergence (Bj6rkman & Holmgren, 1963; Ayodele Cole, 1967; Hadley & Levin, 1969; Mooney & Billings, 1961). Such studies have largely omitted pteridophytes. Owing to the alternation-of-generations life cycle, certain problems arise concerning physiological divergence within groups of pteridophytes. The success of pteridophytes in a community is obviously limited both by the successful establishment of free-living gametophytes and the survival of sporophytes. Thus, the habitat requirements for spore germination and prothallial growth are critical factors for the success of the plant. Physiological divergence between populations or species, as a result of selective pressures of ecologically different habitats, should be apparent in both phases of the pteridophyte life cycle. Farrar (1967) found fern gametophytes reproducing independently in the southern Appalachians, far north of the normal ranges of their sporophytes. Conway (1953) stated that there are few records of finding sporelings of Pteridium aquilinum in Scotland, even though the sporophytes are common and spore production is heavy. She suggested that spores are released late during the growing season and that Pteridium sporelings are more susceptible to frost than are those of other species observed. Conway also noted that sporelings are subject to attack by soil insects and fungi. These two studies suggest that the gametophytic and sporophytic phases of a plant can have different habitat requirements and that one phase of the life cycle can be