The relevance of seed size in modulating leaf physiology and early plant performance in two tree species

he size of seeds and the microsite of seed dispersal may affect the early establishment of seedlings through different physiological processes. Here, we examined the effects of seed size and light availability on seedling growth and survival, and whether such effects were mediated by water use efficiency. Acorns of Quercus petraea and the more drought-tolerant Quercus pyrenaica were sowed within and around a tree canopy gap in a sub-Mediterranean forest stand. We monitored seedling emergence and measured predawn leaf water potential (Ψpd), leaf nitrogen per unit area (Na), leaf mass per area, leaf carbon isotope composition (δ13C) and plant growth at the end of the first summer. Survival was measured on the next year. Path analysis revealed a consistent pattern in both species of higher δ13C as Ψpd decreased and higher δ13C as seedlings emerged later in the season, indicating an increase in 13C as the growing season is shorter and drier. There was a direct positive effect of seed size on δ13C in Q. petraea that was absent in Q. pyrenaica. Leaf δ13C had no effect on growth but the probability of surviving until the second year was higher for those seedlings of Q. pyrenaica that had lower δ13C on the first year. In conclusion, leaf δ13C is affected by seed size, seedling emergence time and the availability of light and water, however, leaf δ13C is irrelevant for first year growth, which is directly dependent on the amount of seed reserves.

Morphological and germination response variability in seeds of wild yellow gentian (Gentiana lutea L.) accessions from northwest Spain

Gentiana lutea L. (yellow gentian, Gentianaceae) is an important medicinal plant under protection as endangered species in most European countries. The aim of this work was to evaluate variation in seed mass, seed water content, and seed germination among 56 wild accessions of G. lutea. The effect of gibberellic acid (GA3), putrescine, moist chilling, and level of ripeness of seeds on subsequent germination was also investigated. Seeds of G. lutea showed physiological dormancy (final germination percentages ranged from 0% to 11%, depending on the accession) and GA3 enhanced seed germination drastically in all the accessions. The highest germination (99%) of GA3-treated seeds was reached at 15 °C. Final germination percentage and germination rate (as expressed by mean germination time), as well as seed mass and seed water content, varied significantly among accessions. In general, 1 year moist chilling did not significantly enhance G. lutea seed germination. For most accessions, no significant differences were found between fully ripe seeds and less ripe seeds for seed water content, seed mass, and seed germination. Applications of GA3 were always most effective than those of putrescine for increasing seed germination.

Germination ecology of the perennial Centaurium somedanum, a specialist species of mountain springs

To improve understanding of how a rare endemic species of Centaurium adapts to a specialized ecological niche, we studied the germination ecology of the mountain spring specialist, C. somedanum, a perennial species restricted to an unusual habitat for this genus. We conducted laboratory experiments with fresh seeds collected from two populations for three consecutive years, to investigate: (1) the effect of temperature and light ongermination; (2) the existence of seed dormancy; and (3) inter-population and inter-annual variation in germinability. Germination occurred only in the light and at relatively low temperatures (15?228C) with no differences between constant and alternating regimes, and a significant decrease at high temperatures (258C and 308C). We found non-deep simple morphophysiological dormancy and variation in seed germinability depending on the year of seed collection. C. somedanum diverged from the common germination characteristics of the genus in: (1) its germination at lower temperatures, which contrasts with what is generally expected in wetland species but could be adaptive in the spring habitat; and (2) its morphophysiological dormancy, which we report here for the first time in the genus and which could be an adaptation to its mountain habitat.

Census, reproductive biology, and germination of Astragalus gines-lopezii (Fabaceae), a narrow and endangered endemic species of SW Spain

Astragalus gines-lopezii Talavera, Podlech, Devesa & F.M.Vázquez (Fabaceae) is a threatened endemic species with a distribution restricted to a very small area in Badajoz Province (Extremadura Region, SW Spain) and only 2 populations are known. This species was catalogued in the ?Endangered? category in the 2008 Red List and the 2010 Threatened Spanish Vascular Flora List. Despite its status as an endangered species, at present very little is known about the distribution, census, and reproductive biology of this species. In this study we have carried out an exhaustive census of A. gines-lopezii , and we have evaluated the production of flowers, fruits, and seeds and the existence or not of intra- and interpopulation variability in seed germination. Results have highlighted the high reproductive capacity of this species on the basis of a high production of flowers, fruits, and seeds. Mechanical scarification of seeds was effective for increasing germination. Thus, initial germination (22%?60%) was increased to 97%?99% when seeds were rubbed with sandpapers. A high intra- and interpopulation variability in seed germination was found in this species. A. gines-lopezii produces seeds with different degrees of physical dormancy, varying this grade among different individuals within a population.

Ecología de la dispersión de plantas en los bosques secos del suroccidente Ecuatoriano

La importancia del proceso de dispersión de semillas en la estructura y dinámica de los ecosistemas es ampliamente reconocida. Sin embargo, para los bosques tropicales estacionalmente secos los estudios relacionados con este proceso son aún escasos y dispersos en comparación con los bosques tropicales lluviosos. En este trabajo se estudió la importancia de los síndromes de dispersión de semillas en la estructuración de comunidades, mediante el análisis de los patrones de dispersión de semillas en el espacio y tiempo para comunidades de leñosas en los bosques secos del suroccidente Ecuatoriano. Esta área forma parte de la región Tumbesina, una de las áreas de endemismo más importantes del mundo, pero también uno de los hotspots más amenazados. El clima se caracteriza por una estación seca que va de mayo a noviembre y una estación lluviosa que se extiende desde diciembre a abril. Para toda esta zona se estima una temperatura promedio anual entre 20° y 26°C y una precipitación promedio anual entre 300 y 700 mm. El trabajo de campo se desarrolló entre febrero de 2009 y septiembre de 2012. El primer paso fue la recopilación de información sobre las especies leñosas nativas de los bosques secos del suroccidente de Ecuador, que permitiera asignar a cada especie a un síndrome de dispersión para determinar el espectro de síndromes de dispersión de semillas. Luego, utilizando la información disponible de 109 parcelas establecidas previamente a lo largo de cuatro cantones de la provincia de Loja que conservan bosques secos en buen estado, se analizó la relación entre el síndrome de dispersión y condiciones ambientales. La relación de los síndromes de dispersión con los patrones espaciales de las especies y con los patrones de la lluvia y banco de semillas se estudió dentro de una parcela permanente de 9 ha, en la Reserva Ecológica Arenillas. Dentro de esta parcela se estableció un transecto de aproximadamente 3,4 km, que se recorrió mensualmente para colectar excretas de cérvidos y analizar el rol de este grupo como dispersor de semillas. Una gran variedad de plantas en los bosques secos tropicales del suroccidente de Ecuador requirió la asistencia de animales para la dispersión de semillas. Sin embargo, un análisis del espectro de dispersión considerando no solo la riqueza, sino también la abundancia relativa de especies, permitió determinar que a pesar de la alta variedad de especies zoócoras, la mayor parte de la comunidad correspondía a individuos anemócoros, que no proveen ninguna recompensa para la dispersión por animales. Este patrón puede deberse a la abundancia relativa de hábitats adecuados para especies con diferente síndrome de dispersión. Las condiciones ambientales afectaron la estructura del espectro de dispersión en la comunidad de bosque seco neotropical estudiada. El análisis de la importancia relativa del síndrome de dispersión y de la heterogeneidad espacial en la formación de patrones espaciales de árboles adultos permitió determinar que la heterogeneidad ambiental ejercía un efecto adicional (y en algunos el único) en la formación de patrones agregados de la mayoría de especies estudiadas. Los resultados señalaron diferencias en los patrones espaciales de las especies dependiendo del síndrome de dispersión, pero también una gran variación en los patrones espaciales incluso entre especies del mismo síndrome de dispersión. El análisis simultáneo de los patrones de la lluvia de semillas y banco de semillas de una comunidad de leñosas y su relación con la vegetación establecida indicaron que la lluvia de semillas era temporalmente variable en número de especies y abundancia de semillas, y dependía del síndrome de dispersión. El síndrome de dispersión también influyó en la formación de bancos de semillas, siendo las especies con capacidad de dispersión limitada (autócoras) las de mayor riqueza de especies y abundancia de semillas. Los cérvidos también se consideraron como un elemento clave en el proceso de dispersión de semillas. Al menos ocho especies leñosas fueron dispersadas legítimamente vía endozoócora. La mayoría de las especies dispersadas presentaron diásporas sin adaptaciones obvias para la dispersión, por lo que la ingestión de semillas por cérvidos se constituye en una vía potencial para la dispersión de sus semillas a largas distancias y, con ello, mejora la posibilidad de colonizar nuevos sitios y mantener el flujo genético. Los resultados de este estudio aportan nuevas evidencias para el entendimiento de la importancia de los procesos de dispersión de semillas en la estructura de los bosques secos neotropicales. Uno de los principales hallazgos a partir de estos cuatro capítulos es que los patrones espaciales de las especies, así como las estrategias que utilizan para dispersarse y hacer frente a las condiciones adversas (es decir, lluvia o banco de semillas) llevan consigo un efecto del síndrome de dispersión, y que la intensidad ese efecto depende a la vez de las condiciones ambientales del lugar. ABSTRACT The importance of seed dispersal process in the estructuring and ecosystem dynamic is widely recongnized. However, for seasonally tropical dry forest studies related to this process are still scarce and scattered compared to tropical rain forests. The present research deals with the importance of seed dispersal syndromes as a driver in the community structure, focusing its attention to temporal and spatial patterns of seed dispersal in woody communities of seasonally dry forest at Southwestern Ecuador. This area is part of the Tumbesian region, one of the most important areas of endemism, but also one of the most threatened areas around the world. Climate is characterized by a dry season from May to November, and a rainy season from December to April. For the whole area an average temperature between 20 ° and 26 ° C, and an average annual rainfall between 300 and 700 mm are estimated. Fieldwork was carried out between February 2009 and September 2012. During a first step information about native woody species of dry forests of southwestern Ecuador was gathered, enabling to assign a dispersal syndrome to each species to determine the seed dispersal spectrum. In a second step, available information from 109 established plots along four municipalities in Loja province, which hold the highest and best conserved dry forest remanants, was analyzed to establish the relationship between dispersal syndromes and environmental conditions. The relationships between dispersal syndromes and species spatial patterns; and between dispersal syndromes and seed rain and seed bank patterns, were studied within a permanent plot of 9 ha, in the Arenillas Ecological Reserve. Within this plot one transect of approximately 3.4 km was set to collect monthly deer droppings, which were used to latter analyze the rol of this group as seed dispersers. The results showed that a large variety of plants in tropical dry forest of Southwestern Ecuador require animal assistance to dispers their seeds. However, an analysis of seed dispersal spectrum considering not only species richness, but also the relative abundance of species, allowed to determine that despite the high variety of zoochorous species, most individuals in the community corresponds to anemochoruos species. This shift may be due to the relative abundance of habitats that are suitable for species with different dispersal syndromes. Moreover, quantitative data analysis showed that environmental conditions affect the structure of seed dispersal spectrum in the studied community. The analysis of relative importance of dispersal syndrome, and the environmental heterogeneity on formation of adult trees spatial patterns, indicated that environmental heterogeneity exert an additional (or was the only) effect limiting the distribution of most species in this forest. The findings showed differences in spatial patterns related to dispersal syndrome, but also showed a large variation in spatial patterns even among species sharing the same dispersal syndrome. Simultaneous analysis of seed rain and seed bank patterns of a woody community, and their relationship with established vegetation, suggested that seed rain is temporally variable in species number and seeds abundance, and that variation is related to the dispersal syndrome. Dispersal syndrome also influenced on the formation of seed banks, being species with limited dispersal abilities (autochorous) the ones with highest species richness and seed abundance. Deer were found as a key element in the seed dispersal process. At least to eight woody species were dispersed legitimately by ingestion. Diaspores of most dispersed species had no obvious adaptations to seed dispersal, therefore, seed ingestion by deer represents a potential pathway for long-distance dispersal, and hence, improves the chances to colonizing new sites and to maintain gene flow. Overall, these results provide new evidence for understanding the importance of seed dispersal processes in the structure of Neotropical dry forests. One of the major findings from these four chapters is that spatial patterns of species, and the strategies used to disperse their seeds and to deal with the adverse conditions (i.e. seed rain or seed bank) are related with dispersal syndromes, and the intensity of that relation depends in turn, on environmental conditions.

Census, reproductive biology, and germination of Astragalus gines-lopezii (Fabaceae),a narrow and endangered endemic species of SW Spain.

Astragalus gines-lopezii Talavera, Podlech, Devesa & F.M.Vazquez (Fabaceae) is a threatened endemic species with a distribution restricted to a very small area in Badajoz Province (Extremadura Region, SW Spain) and only 2 populations are known.This species was catalogued in the "Endangered" category in the 2008 Red List and the 2010 Threatened Spanish Vascular Flora List. Despite its status as an endangered species, at present very little is known about the distribution, census, and reproductive biology of this species. In this study we have carried out anexhaustive census of A. gines-lopezii, and we have evaluated the production of flowers, fruits, and seeds and the existence or not of intra- and interpopulation variability in seed germination. Results have highlighted the high reproductive capacity of this species on the basis of a high production of flowers, fruits, and seeds. Mechanical scarification of seeds was effective for increasing germination. Thus, initial germination (22%-60%) was increased to 97%-99% when seeds were rubbed with sandpapers. A high intra- and interpopulation variability in seed germination was found in this species. A. gines-lopezii produces seeds with different degrees of physical dormancy, varying this grade among different individuals within a population.

Regenerative morphological traits in a woody species community in Tumbesian tropical dry forest.

The study of functional morphological traits enables us to know fundamental aspects of the dynamics of plant communities in local and global habitats. Regenerative morphological traits play an important role in defining plant history and ecological behavior. Seed and fruit characteristics determine to a large extent the patterns for dispersal, germination, establishment and seedling recruitment a given species exhibits on its natural habitat. Despite their prominent role, seed and fruit traits have been poorly studied at the community level of woody plant species in neo-tropical dry forests. In the present study we aimed at i) evaluate the functional role of morphological traits of seeds, fruits and embryo in woody plant species; ii) determine which are the morphological patterns present in seeds collected from the community of woody species that occur in neo-tropical dry forests; and iii) compare woody plant species seed mass values comparatively between neo-tropical dry and tropical forests. To do so, mature seeds were collected from 79 plant species that occur in the Tumbesian forest of Southwest Ecuador. The studied species included the 42 and 37 most representative tree and shrubbery species of the Tumbesian forest respectively. A total of 18 morphological traits (seven quantitative and 11 qualitative) were measured and evaluated in the seeds, fruits and embryos of the selected species, and we compared the seeds mass with other forest types. Our results showed a huge heterogeneity among traits values in the studied species. Seed mass, volume and number were the traits that vary the most at the community level, i.e. seed length ranged from 1.3 to 39 mm, and seed width from 0.6 to 25 mm. Only six embryo types were found among the 79 plant species. In 40 % of the cases, fully developed inverted embryos with large and thick cotyledons to store considerable amount of nutrients were recorded. We concluded that highly variable and functionally complementary morphological traits occur among the studied woody plants of the dry Tumbesian forest. The latter favors a plethora of behavioral mechanisms to coexist among woody species of the dry forest in response to the environmental stress that is typical of arid areas.

(Tables 1,2) Viability of Poa trivialis seeds transported to Antarctica from different locations

Antarctic ecosystems are at risk from the introduction of invasive species. The first step in the process of invasion is the transportation of alien species to Antarctic in a viable state. However, the effect of long-distance human-mediated dispersal, over different time-scales, on propagule viability is not well known. We assessed the viability of Poa trivialis seeds transported to Antarctica from the UK, South Africa and Australia by ship or by ship and aircraft. Following transportation to the Antarctic Treaty area, no reduction in seed viability was found, despite journey times lasting up to 284 days and seeds experiencing temperatures as low as -1.5°C. This work confirms that human-mediated transport may overcome the dispersal barrier for some propagules, and highlights the need for effective pre-departure biosecurity measures.

Seed characteristics of 42 economically important species of Solanaceae in the United States /

Bibliography: p. 31-32.

Direct seeding to restore rainforest species: Microsite effects on the early establishment and growth of rainforest tree seedlings on degraded land in the wet tropics of Australia

Reforestation in tropical areas is usually attempted by planting seedlings but, direct seeding (the artificial addition or sowing of seed) may be an alternative way of accelerating forest recovery and successional processes. This study investigated the effects of various sowing treatments (designed to create different microsite conditions for seed germination) and seed sizes on the early establishment and growth of directly sown rainforest tree species in a variety of experimental plots at three sites in the wet tropical region of north-cast Queensland, Australia. The different sowing treatments were found to have significant effects on seedling establishment. Broadcast sowing treatments were ineffective and resulted in very poor seedling establishment and high seed wastage. Higher establishment rates occurred when seeds were buried. Seed size was found to be an important factor affecting establishment in relation to micro-site condition. In general, larger seeded species had higher establishment rates at all three sites than species of small and intermediate seed size, but only in sowing treatments where seeds were buried. Overall these results suggest that direct sowing of seed can be used as a too] to accelerate recolonisation of certain rainforest tree species on degraded tropical lands, but initial success will be dependent on the choice of sowing method and its suitability for the seed types selected. The results also indicate that the recruitment of naturally dispersed tree species at degraded sites is likely to be severely limited by the availability of suitable microsites for seed germination. Consequently the natural recovery of degraded sites via seed rain can be expected to be slow and unpredictable, particularly in areas where soil compaction has occurred. (c) 2006 Elsevier B.V. All rights reserved.

Study of the effects of climate warming on seed germination and seed longevity of snowbed species

Understanding how climate change will affect the distribution and the phenology of plants is becoming an increasingly important topic in ecological studies. In response to climate warming, there are documented upward shift and alterations of phenology and physiology of several plant species. Despite this, the effects of climate change on plant regeneration from seeds have largely been neglected. However, regeneration from seeds, a key event in the plant life cycle, could be significantly affected by climate warming. In this regard, we investigated how climatic changes will affect the seasonal dynamics of seed germination and seedling survival in two different alpine context. The first part refers to five species inhabiting a snowbed located at the Gavia pass (Parco Naturale dello Stelvio). Here, plants were exposed, in the field, to natural conditions and to artificial warming using Open Top Chambers proposed by the ITEX (International Tundra Experiment). The germination curves of seeds produced were compared in order to highlight differences in seed germination ecology and in seed physiology induced by the climate warming. In the second part, we considered two tree species that form the treeline in Davos (Switzerland). As a surrogate of climate warming we used the natural thermal gradient driven by the altitude and we compared the germination behavior of the species studied in three sites at three different elevations in order to evaluate the likelihood of treeline shift under the predicted climate warming.

Seed and vegetative propagation methods for the rare Florida native species Chionanthus pygmaeus (pygmy fringetree)

Chionanthus pygmaeus Small (pygmy fringetree) (Oleaceae) is an endemic and rare Florida species, which has an attractive, small habit giving it great potential for use in managed landscapes. Members of the genus Chionanthus are difficult to propagate via cuttings and possess complex seed dormancies that are not well understood. Conservation of pygmy fringetree and its potential for commercial propagation for use in managed landscapes is contingent on a better understanding of its complex seed dormancy and enhancement of its propagation. I conducted two experiments to assess sexual and asexual propagation methods for pygmy fringetree. The first experiment was conducted to determine what factors are involved in overcoming seed dormancy. Various scarification treatments, which mimicked conditions seeds are exposed to in the wild, were investigated to determine their effects on germination of 20-year-old seeds originally collected from the species’ native range. Treatments included endocarp removal, sulfuric acid, boiling-water, and smoke-water treatments. Prior to treatment initiation, seed viability was estimated to be 12%. Treated seeds went through two cold- and two warm-stratification periods of 4°C and 25°C, respectively, in a dark growth chamber. After 180 days, none of the treatments induced early germination. Seeds were then tested for viability, which was 11%. Seed dormancy of the species is apparently complex, allowing some of the seeds to retain some degree of viability, but without dormancy requirements satisfied. The second experiment was conducted to assess if pygmy fringetree could be successfully propagated via hardwood or root cuttings if the appropriate combination of environmental conditions and hormones were applied. Hardwood and root cuttings were treated with either 1000 ppm IBA talc, 8000 ppm IBA talc, or inert talc. All cuttings were placed on a mist bench in a greenhouse for 9 weeks. Hardwood cuttings were supplemented with bottom heat at 24 °C. No treatments were successful in inducing adventitious root formation. I conclude that pygmy fringetree seeds possess complex dormancy that was not able to be overcome by the treatments utilized. However, this result is confounded by the age of the seeds used in the experiment. I also conclude that vegetative propagation of pygmy fringetree is highly dependent on the time of year cuttings are harvested. Further research of both seed and asexual propagation methods need to be explored before pygmy fringetree can be propagated on a commercial scale.

Characterisation of accessions and species of Macadamia to stem infection by Phytophthora cinnamomi

Phytophthora cinnamomi is a major pathogen in most macadamia plantations worldwide. Due to stem lesions, stem cankers and leaf defoliation it results in loss of productivity and tree death. In this study we examined accessions of the four Macadamia species and their hybrids, produced via rooted stem cuttings or germinated seeds, for susceptibility to stem canker and necrotic lesion caused by P. cinnamomi. Plants were wound-inoculated with agar containing P. cinnamomi. The symptoms produced in inoculated plants were used to characterize host susceptibility variation within and among the population. Lesion lengths and severity of stem canker were recorded. The four species and hybrids differed significantly in stem canker severity (P < 0.001) and lesion length (P = 0.04). M. integrifolia and M. tetraphylla hybrids were the most susceptible. M. integrifolia had the greatest stem canker severity and the most extensive lesions above and below the site of inoculation. Restricted lesion sizes were observed in M. ternifolia and M. jansenii. The effects of basal stem diameter and the method of propagation either from cuttings or seed were not significant. The genetic variation in the reactions of macadamia accessions to stem infection by P. cinnamomi is discussed.

Prevalence of colonizing bacteria and their association with primary bacteremias in hemodialysis of a university hospital

to be from 2.5 to 5.5 cases per 1,000 catheter-day. the clinical impact is relevant and increases the cost of the HD Unit. Methods: The present study is the irst of 2 phases. It was conducted from January to December of 2012, and included all patients and nurses who were in the HD Unit. The prevalence of Gramnegative bacilli (GNB) and methicillin-resistant Staphylococcus aureus (MrSA) colonizing the nasal passages and the skin is described. Also, phenotypic association was sought by genus, species and sensitivities between colonizing bacterial strains and blood cultures with GNB and MRSA. Results: the study included 70 patients and 10 nurses. the prevalence of nasal colonization in patients by GNB was 9% and 6% in the pericatheter, and no nursing GNB colonization was discovered. The prevalence of MRSA nasal colonization was 19% and 6% in the pericatheter for patients and in the nurses the nasal colonization was 50% and 10% in the hands. We identiied 29 cases of primary bacteremia. The primary bacteremia rate is 1.5 per 1,000 catheter-day or 0.4 episodes per patient per year. Conclusion: We demonstrated a high prevalence of MrSA colonization in patients and nurses in the HD Unit. No relationship was found between primary bacteremia by GNB and patients and nurses’ bacteria colonization by the phenotypic comparison.