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Description of the subject. Essential oils are volatile fractions produced through the special metabolism of plants. One significant biological application of essential oils in recent years has been their use as bioherbicides, due to their important biocide effect. Objectives. This study aims to identify the chemical constituents of Aloysia gratissima (Gillies & Hook.) Tronc. essential oil and assess its biocide potential. Method. This study describes, for the first time, the chemical constitution of the essential oils from seeds of A. gratissima. To verify possible biocide effect, lettuce seeds were submitted to different concentrations of essential oils from A. gratissima leaves (AG-LE-EO), flowers (AG-FL-EO), and seeds (AG-SE-EO) to evaluate germination percentage, mean germination time, synchrony of germination, and seedling length. . Results. At concentrations of 800 µl l-1, synchrony was positively influenced by (AG-LE-EO), increasing from 0.38 to 0.54. On the other hand, AG-SE-EO at concentrations of 800 µl·l-1 reduced lettuce germination from 90.8% to 64.4% and seedling length from 1.35 to 0.8 cm, besides increasing mean germination time, indicating biocide effects. Conclusions. These results are expected to lead to further trials to understand how the constituents of A. gratissima essential oils inhibit germination, making them a potential bioherbicide.

Description of the subject. Spanish sage or chia (Salvia hispanica) has attracted increasing interest over the last decade due to the composition of its seeds. It is now cultivated in several European countries. Objectives. The aims of this study were to investigate the oil content and composition of seeds from chia cultivated over a three-year period in South-West France. Method. The cultivar Oruro (Panam, France) was used for this study. It was cultivated in 2014, 2015 and 2017 at Villemur-sur-Tarn (South-West France). Oil, ash and protein contents (Kjeldahl) was assessed, fatty acids (GC-FID), sterols (GC), tocopherols (HPLC) composition was determined on seeds. Results. Cultivation year affected oil, protein and ash contents, and the content and composition of fatty acid, sterols and tocopherols. Oil (range of 30.6-34.7%) and ash (4.8-5.2%) contents were higher in 2014 and 2015 (higher rainfall than 2017). Protein content was higher in 2017 (21.7%) than in the other two years (17.5-19.9%). This trend was expected, given the negative correlation between oil and protein contents. Polyunsaturated fatty acids predominated, and their levels were highest in 2015 and lowest in 2017. Saturated and monounsaturated fatty acid levels followed the opposite pattern (lowest in 2015 and highest in 2017). Sterols and tocopherols accumulated to higher levels in the seeds in 2014 than in 2017. Conclusions. All the seed quality traits of chia cultivated in France were affected by the climatic conditions of the year of cultivation. Effet de l'année de culture sur la teneur en huile et la composition en acides gras des graines de chia (Salvia hispanica L.) en France Description du sujet. La sauge espagnole ou chia (Salvia hispanica) a suscité, en raison de la composition de ses graines, un intérêt croissant au cours de la dernière décennie. Elle est maintenant cultivée dans plusieurs pays européens. Objectifs. Les buts de cette étude étaient d'examiner la teneur en huile et la composition des graines de chia cultivées durant trois années dans le sud-ouest de la France. Les teneurs en huile, en cendres et en protéines ont été évaluées, la composition en acides gras, stérols et tocophérols a été déterminée dans les graines. Methode. Le cultivar Oruro (Panam, France) a été utilisé et cultivé en 2014, 2015 et 2017 à Villemur-sur-Tarn (sud-ouest de la France). Resultats. L'année de culture a affecté les teneurs en huile, en protéines (Kjeldahl) et en cendres, ainsi que la teneur et la composition en acides gras (GC-FID), en stérols (GC) et en tocophérols (HPLC). Les teneurs en huile (comprises entre 30,6 et 34,7 %) et en cendres (4,8-5,2 %) étaient plus élevées en 2014 et 2015 (pluviométrie plus importante qu'en 2017). La teneur en protéines était plus élevée en 2017 (21,7 %) que les deux autres années (17,5 et 19,9 %). Cette tendance était attendue, étant donné la corrélation négative entre les teneurs en huile et en protéines. Les acides gras polyinsaturés ont prédominé et leurs teneurs étaient les plus élevées en 2015 et les plus faibles en 2017. Les teneurs en acides gras saturés et monoinsaturés ont suivi le schéma inverse (les plus faibles en 2015 et les plus élevées en 2017). Les stérols et les tocophérols se sont accumulés à des niveaux plus élevés dans les graines en 2014 qu'en 2017. Conclusions. Ainsi, tous les traits de qualité des graines de chia cultivées en France ont été affectés par les conditions climatiques de l'année de culture.

We developed a model of hardwood tree colonization in forest patches. We began with a basic model of species' recruitment density calculated as a function of seed production and juvenile survivorship. Survivorship probability was expressed as a function of seed size, using seed-sowing data for a wide variety of species. To account for dispersal, we used an exponential distancedecay function based on empirical colonization data for species classified by dispersal mechanism and seed mass. The basic model reasonably predicted observed recruitment densities at or near forest edges, except for small seeded, wind-dispersed species with strong establishment constraints, for which it over-predicts. Our dispersal term yielded predictions that were not statistically different from observed colonization. However, species with large seeds and unspecialized dispersal mechanism appear to have distinct thresholds beyond which no dispersal occurs. Further research should better account for establishment constraints among small-seeded species, dispersal constraints among large-seeded species and unspecialized dispersers, and improve the dispersal functions to better reflect vectors such as birds. Nevertheless, the present model is adequate for the prediction of colonization probabilities in fragmented forests, requiring only an estimate of the abundance of source trees of a species and the mean inter-fragment distances.

Native seed is often collected en masse from remnant ecosystems to supply landscape-scale restoration. Successful large-scale restoration depends on sustained seed yields but also on donor population persistence. Native plants that reproduce solely by seed are especially sensitive to harvesting practices. We addressed the challenge of procuring sufficient seed from remnant sources to restore landscapes while also maintaining remnant populations of native plants. We evaluated: 1) the sustainability of seed harvest at varying intensities in Rudbeckia hirta, a seedreliant plant; and 2) the contribution of fire in promoting sustainability of seed donor populations. We planted seedlings of R. hirta in a field experiment that manipulated management type (burned or unburned) and harvest intensity (0, 50%, or 100% seed removed), and measured changes in seedling recruitment and seed production among treatments. Moderate intensity harvest and burning did not significantly reduce seedling recruitment, but high intensity harvest with burning reduced recruitment by 95% compared to controls. Seed production nearly doubled in burned treatments. In unburned prairie, recruitment is negligible, and harvest intensity does not have an effect on recruitment. For harvest-sensitive prairie species, a strategy incorporating moderate intensity seed harvest with burning is most likely to provide seed for large-scale restoration sustainably.

This study investigated the effect of high temperature and drought (during grain-filling) on the quality and components yield of five winter wheat varieties. Drought and drought + heat were found to have a much greater influence on the yield and quality than heat stress alone. Averaged over the varieties, the yield losses were 57% after drought, 76% after drought + heat, and only 31% after heat stresses. The reductions in the unextractable polymeric protein fraction and glutenin-to-gliadin ratio indicated a poorer grain yield quality, despite the higher protein content. Quality deterioration was observed after drought or drought + heat, while high temperatures alone resulted in no change or in a better ratio of protein components. A significant negative correlation was observed between starch granule size and relative protein content after drought.

The testa of higher plant seeds protects the embryo against adverse environmental conditions. Its role is assumed mainly by controlling germination through dormancy imposition and by limiting the detrimental activity of physical and biological agents during seed storage. To analyze the function of the testa in the model plant Arabidopsis, we compared mutants affected in testa pigmentation and/or structure for dormancy, germination, and storability. The seeds of most mutants exhibited reduced dormancy. Moreover, unlike wild-type testas, mutant testas were permeable to tetrazolium salts. These altered dormancy and tetrazolium uptake properties were related to defects in the pigmentation of the endothelium and its neighboring crushed parenchymatic layers, as determined by vanillin staining and microscopic observations. Structural aberrations such as missing layers or a modified epidermal layer in specific mutants also affected dormancy levels and permeability to tetrazolium. Both structural and pigmentation mutants deteriorated faster than the wild types during natural aging at room temperature, with structural mutants being the most strongly affected.

Seed dispersal by animals is a key interaction, with effects on the population ecology and evolution of many plant lineages. Despite the fact that infrequent seed dispersers can potentially provide important services to plant populations, little attention has been paid so far to scarce mutualists. We assessed different aspects of quantity and quality of seed dispersal from fruit removal to seed germination in the Iberian pear, Pyrus bourgaeana, finding that fruit consumers markedly differed in the nature of their interaction with the tree. Whereas the abundant rodents, rabbits, and deer damaged all seeds eaten, the uncommon carnivores badger and fox and the abundant boars dispersed a large fraction of ingested seeds as viable propagules, acting as legitimate seed dispersers. Despite low rates of visitation by badgers to fruiting trees, they transported more viable seeds than the abundant boars, due to better seed treatment and a higher feeding rate on pears. Seed dispersal by all 3 legitimate dispersers, especially the badger, enhanced post-dispersal P. bourgaeana seed survival, supporting the “escape” predation hypothesis. Pyrus bourgaeana showed relatively high frequencies of visits by a myriad of frugivores; however, it relied on the dispersal service provided by an infrequent carnivore, the badger, rather than on those provided by the abundant mammalian herbivores. Therefore, under some circumstances, uncommon animal counterparts play major roles in their mutualistic interactions with flowering plants. Nomenclature: Váldes et al., 2007.

Studies of tree recruitment are many, but they provide few general insights into the role of recruitment limitation for population dynamics. That role depends on the vital rates (transitions) from seed production to sapling stages and on overall population growth. To determine the state of our understanding of recruitment limitation we examined how well we can estimate parameters corresponding to these vital rates. Our two-part analysis consists of (1) a survey of published literature to determine the spatial and temporal scale of sampling that is basis for parameter estimates, and (2) an analysis of extensive data sets to evaluate sampling intensity found in the literature. We find that published studies focus on fine spatial scales, emphasizing large numbers of small samples within a single stand, and tend not to sample multiple stands or variability across landscapes. Where multiple stands are sampled, sampling is often inconsistent. Sampling of seed rain, seed banks, and seedlings typically span <1 yr and rarely last 5 yr. Most studies of seeding establishment and growth consider effects of a single variable and a single life history stage. By examining how parameter estimates are affected by the spatial and temporal extent of sampling we find that few published studies are sufficiently extensive to capture the variability in recruitment stages. Early recruitment stages are especially variable and require samples across multiple years and multiple stands. Ironically, the longest duration data sets are used to estimate mortality rates, which are less variable (in time) than are early life history stages. Because variables that affect recruitment rates interact, studies of these interactions are needed to assess their full impacts. We conclude that greater attention to spatially extensive and longer duration sampling for early life history stages is needed to assess the role of recruitment limitation in forests.

Interactions between ants and vertebrate-dispersed fleshy fruits are common on the floor of tropical forests. These interactions are considered beneficial to seeds if ants clean the seed (which may prevent fungal contamination and/or increase germination success) or act as secondary fine-scale dispersers (depositing the seed in nearby nutrient-enriched nest sites). Benefits to seeds, however, may be constrained by limited ant access to fruits. Here, we experimentally tested whether ant access to fallen fleshy fruits of Psychotria suterella (Rubiaceae) can be affected by previous handling (including ingestion) by birds. We found that mandibulated fruits and fruits embedded in feces are more prone to be visited by ants compared to entirely intact fruits. Moreover, the number of ant species per station was higher for vertebrate-handled fruit categories. We suggest that ongoing vertebrate loss in tropical forests may affect this highly opportunistic and potentially mutualistic interaction.