Search

Bambara groundnut (Vigna subterranean (L) Verdc) is an indigenous African crop. In South Africa, the crop is grown by rural subsistence farmers. This crop is classified as a drought-tolerant crop and it can produce good yields in poor soil conditions. However, statistics show that Bambara groundnut production is currently neglected by industries due to the lack of research on the crop focused on postharvest technologies, and agro-processing. Current research on the crop is mostly focused on agronomic and growing characteristics. Data on the physical properties and processing equipment for the Bambara groundnuts are limited. The objectives of this study were to investigate the effect of moisture contents on both Bambara groundnut seeds (shelled) and pods (unshelled). The physical properties of the pods and seeds were measured at three moisture content levels. The finding showed that axial dimensions, geometric mean diameter, sphericity, volume, and weight increase as moisture content increases. The static coefficient of friction of seeds and pods increased from 0.15 to 0.19 and 0.29 to 0.31, respectively. Simirlarly, the bulk density of shelled and unshelled groundnuts increased from 500 to 955, and 355 to 422 kg.[m.sup.-3], respectively. The results also showed that the true density of seeds rose from 994 to 1832 kg.[m.sup.-3] and for the unshelled groundnuts it increased linearly from 532 to 655 kg.[m.sup.-3]. The required forces for cracking both bambara groundnut seeds and kernels showed a declining trend as moisture increased from 6 to 20%. The cracking forces required for Bambara groundnuts kernels at 6, 15, and 20 % are 32.5 [+ or -]12 N, 29.9 [+ or -]15.3 N, and 28.9 [+ or -]9 N, respectively. As the moisture increased, the data deviation from the mean decreased from 16.30 to 10.1 N. In terms of designing agro processing eqiupment or machinary such as a shelling machine, the physical properties from the lower moisture content are recommended. Key words: cracking force, physical properties, moisture content, Bambara groundnuts, INTRODUCTION Bambara groundnut (Vigna subterranean (L) Verdc) is an African legume crop that is currently neglected by commercial farms [1, 2]. This crop serves as a cheap and high-quality protein [...]

In many but not all recalcitrant Quercus seeds, water loss during drying only occurs through the scar. Consequently, the embryo axis sitting on the opposite side of the scar is well protected from desiccation. However, whether such a mechanism is common throughout Fagaceae species is unexplored. Similarly, little is known about the desiccation response of other Fagaceae genera. Germination and desiccation tolerance of Castanopsis sclerophylla (Lindl. & Paxton) Schottky (Fagaceae) were studied by drying the seeds with silica gel. Fresh seeds had a moisture content (MC) of 36% and germinated to 92.5% when incubated at 15/20 [degrees]C. Drying seeds to 22.5% and 20.7% MC decreased germination to 27% and 5%, respectively, indicating that seeds are recalcitrant. X-ray computed tomography and photomicrographs showed that the embryo axis of C. sclerophylla is located just below the scar. Regardless of drying occurring either through only the scar or the whole pericarp, embryo drying was deemed unavoidable. Nevertheless, germination percentage during drying showed exceptional similarities with the other Fagaceae species. Key words: Quercus, pericarp, embryo position, morphology, recalcitrant. Dans de nombreuses graines recalcitrantes de Quercus, mais pas toutes, la perte d'eau pendant le sechage se produit uniquement par la cicatrice. Par consequent, l'axe de l'embryon situe du cote oppose de la cicatrice est bien protege de la dessiccation. Cependant, la question de savoir si un tel mecanisme est commun a toutes les especes de Fagaceae n'a pas ete exploree. De meme, on sait peu de choses sur la reponse a la dessiccation des autres genres de Fagaceae. La germination et la tolerance a la dessiccation de Castanopsis sclerophylla (Lindl. & Paxton) Schottky (Fagaceae) ont ete etudiees en sechant les graines avec du gel de silice. Les graines fraiches comportaient un taux d'humidite de 36 % et germaient a 92,5 % lorsqu'elles etaient incubees a 15[degrees]/20 [degrees]C. Le sechage des graines a 22,5 % et 20,7 % d'humidite reduisait la germination a 27 % et 5 %, respectivement, ce qui indique que les graines sont recalcitrantes. La tomographie a rayons X assistee par ordinateur et les photomicrographies ont montre que l'axe de l'embryon de C. sclerophylla est situe juste en dessous de la cicatrice. Independamment du fait que le sechage se produise soit a travers la cicatrice seulement, soit a travers le pericarpe entier, le sechage de l'embryon a ete juge inevitable. Neanmoins, le pourcentage de germination pendant le sechage montrait une remarquable similitude avec les autres especes de Fagaceae. [Traduit par la Redaction] Mots-cles : Quercus, pericarpe, position de l'embryon, morphologie, recalcitrant., Introduction Two broad groups of seeds have been recognized by Roberts (1973) for their ability to withstand drying. One group includes nearly 90% of the known plant species with seeds [...]

To understand the reproductive ecology of a plant species with both selfing and outcrossing reproductive systems, it is important to know how selfed individuals contribute to the maintenance of a population. Further, examination of the magnitude of inbreeding depression after pollination is essential for the accurate measurement of reproductive success. In this study, we investigated the characteristics of viable seeds and seedlings of Rhododendron kaempferi Planch. in a region where the bumblebee pollinator Bombus ardens Smith, 1879 are abundant. In a hand-pollination experiment, the fruit set from self-pollination was 32%, significantly lower than that from outcross-pollination (81%). The number of seeds per fruit from self-pollination was one sixth the number from outcross-pollination. However, the number of seeds per fruit was negatively correlated with the mass per seed. In addition, the germination rate was low when the seed mass was light. Although selfed seeds could germinate, 89% of the seedlings died within a year. The inbreeding depression coefficient one year after sowing was very high (0.89). These results indicate that R. kaempferi shows extremely strong selection for outcrossing but maintains a slight selfing potential in a natural population in central Japan. Key words: bumblebee, germination, inbreeding depression, rhododendron, seed. Afin de comprendre l'ecologie de la reproduction d'especes vegetales dont les systemes de reproduction sont a la fois endogames et par croisements eloignes, il est important de savoir comment les individus endogames contribuent au maintien d'une population. De plus, l'examen de l'ampleur de la depression de consanguinite apres la pollinisation est essentiel pour mesurer precisement le succes de la reproduction. Dans cette etude, les auteurs ont examine les caracteristiques des graines et des plantules viables de Rhododendron kaempferi Planch. dans une region ou le bourdon pollinisateur Bombus ardens Smith, 1879 est abondant. Lors d'une experience de pollinisation manuelle, la nouaison issue de l'autopollinisation etait de 32 %, soit nettement moins que celle issue de la pollinisation croisee (81 %). Le nombre de graines par fruit provenant de l'autopollinisation etait un sixieme de celui provenant de la pollinisation croisee. Cependant, le nombre de graines par fruit etait correle negativement avec le poids par graine. Par ailleurs, le taux de germination etait faible lorsque le poids des graines etait leger. Bien que les graines endogames aient pu germer, 89 % des plantules mouraient au cours de la premiere annee. Le coefficient de depression de consanguinite un an apres le semis etait tres eleve (0,89). Ces resultats indiquent que R. kaempferi presente une selection extremement forte pour les croisements eloignes, mais maintient un leger potentiel d'autofecondation dans une population naturelle du centre du Japon. [Traduit par la Redaction] Mots-cles : bourdon, germination, depression de consanguinite, rhododendron, graine., Introduction Inbreeding depression, defined as the reduction in fitness of progeny derived from inbreeding relative to that of progeny derived from outcrossing, has long been an important topic in the [...]

We used microsatellite genetic markers to evaluate the mating system of western red cedar (Thuja plicata Donn ex D. Don) under various seed orchard pollen management schemes. We primarily examined whether supplemental mass pollination (SMP) can reduce the observed selfing rates. Pollen blowing and 'hooding' were also examined in smaller tests. Only SMP was consistently effective in reducing the selfing rate, from 30% to 20%. The correlation of paternity was quite high (60%-90%) in two of three orchards, and in these two orchards the application of SMP reduced this correlation by about 10% as well. The correlation of paternity is the fraction of full-sibling vs. half-sibling progeny, and unbiased estimates can be obtained with few loci, even single loci, in contrast to other types of paternity analysis. We also find the microsatellite amplicon sizes should be pooled into 'bins' of 2-4 nucleotides, owing to unintended errors of assay; otherwise the estimates are biased. This new feature of mating system estimation was incorporated into the computer program MLTR. Key words: self-fertilization, correlated paternity, supplemental mass pollination, western red cedar. Les auteurs ont utilisé des marqueurs génétiques microsatellites afin d'évaluer le système de fécondation du thuya géant (Thuja plicata Donn ex D. Don) dans le cadre de divers programmes de gestion du pollen de vergers à graines. Ils ont d'abord examiné si une pollinisation de masse supplémentaire (PMS) peut réduire les taux d'autofécondation observés. Le soufflage et le << capuchonnage >> (<< hooding >>) du pollen ont aussi été examinés lors de tests à plus petite échelle. Seule la PMS était efficace de façon constante pour réduire le taux d'autofécondation de 30% à 20%. La corrélation de la paternité était relativement élevée (60-90%) dans deux des trois vergers et dans ces deux vergers, l'application de la PMS réduisait aussi cette corrélation d'environ 10%. La corrélation de la paternité consiste en la fraction de pleins germains par rapport à la demi-fratrie dans la progéniture, et des estimations non biaisées peuvent être obtenues avec peu de locus, et même un seul locus, comparativement aux autres types d'analyse de paternité. Les auteurs ont aussi constaté que les tailles des amplicons microsatellites devraient être regroupées en << classes >> (bins) de 2-4 nucléotides, en raison d'erreurs involontaires du test; sinon, les estimations sont biaisées. Cette nouvelle caractéristique du système de fécondation a été incorporée au programme informatique MLTR. [Traduit par la Rédaction] Mots-clés : autofécondation, paternité corrélée, pollinisation de masse supplémentaire, thuya géant., Introduction Seed orchards connect the generations between domesticated trees and deliver genetically improved trees to natural populations. In British Columbia, there are seed orchards for two species of angiosperms and [...]

In this study, salt tolerance during germination of Aeluropus lagopoides (L.) Trin. was tested using fresh seeds collected from three different maternal habitats under three thermoperiods and two light regimes. Additionally, we tested the ability of non-germinated seeds that had been exposed to different concentrations of NaCl to recover their germination in distilled water. The results showed a significant effect of seed source, temperature, and salinity, and some of their two- and three-way interactions on final germination and recovery percentage. The seeds from non-saline provenances had the highest percentages for germination (ca. 79%) under the 35/25 [degrees]C temperature regime, whereas the lowest percentages for germination (ca. 21%) was recorded for seeds from saline conditions under the 25/15 [degrees]C treatment. Additionally, percent germination was significantly lower for the seeds incubated in the saline solutions (100, 200, 400, and 600 mmol/L NaCl) and germinated under colder conditions (15/25 [degrees]C), compared with the seeds incubated in non-saline solutions (control group, 0 mmol/L NaCl) and germinated under warmer conditions (35/25 [degrees]C). The highest recovery percentage was recorded for seeds of the hyper-saline habitat incubated at 35/25 [degrees]C. Thus, seeds maintained their viability despite experiencing a range of saline conditions and were able to germinate upon the arrival of suitable conditions, which can be an adaptation to its saline arid desert habitat. Key words: Aeluropus lagopoides, germination recovery, maternal habitat, photoperiod, salinity, thermoperiod. Resume : Dans cette etude, la tolerance au sel lors de la germination de Aeluropus lagopoides (L.) Trin. a ete testee sur des semences fraiches recoltees de trois habitats maternels differents, selon trois thermoperiodes et deux regimes de luminosite. De plus, la capacite de semences non germees de recuperer leur potentiel de germination dans l'eau distillee apres avoir ete soumises a differentes concentrations de NaCl a ete testee. Les resultats ont montre un effet significatif de la source des semences, de la temperature et de la salinite prises separement, deux a deux ou toutes les trois, sur la germination et le pourcentage de recuperation. Les semences provenant d'habitats non salins presentaient la germination la plus elevee (environ 79 %) a un regime de temperature de 35/25 [degrees]C, alors que la germination la plus faible (environ 21 %) etait enregistree chez les semences en conditions salines a des temperatures de 25/15 [degrees]C. Par ailleurs, la germination etait significativement plus faible a partir d'une incubation dans une solution non saline - controle (0 mmol/L NaCl) a des temperatures plus chaudes (35/25 [degrees]C) vers une incubation dans des solutions salines (100, 200, 400 et 600 mmol/L NaCl) a des temperatures plus froides (15/25 [degrees]C). Le pourcentage de recuperation le plus eleve etait enregistre chez les semences provenant d'un habitat hypersalin incubees a 35/25 [degrees]C. Ainsi, les semences maintenaient leur viabilite malgre le fait d'etre exposees a un spectre de conditions salines et elles etaient capables de germer lors de l'arrivee de conditions adequates, ce qui peut constituer une adaptation a leur habitat aride salin desertique. [Traduit par la Redaction] Mots-cles : Aeluropus lagopoides, recuperation de la germination, habitat maternel, photoperiode, salinite, thermoperiode., Introduction Desert plants generally experience extreme aridity, large fluctuations of water availability, and a relatively short growing season (Omar and Bhat 2008). For several desert plant species, the availability of [...]

Pre-harvest soybean seeds in the field are susceptible to high temperature and humidity (HTH) stress, leading to pre-harvest seed deterioration, which will result in a reduction in grain quality, yield, and seed vigor. To understand the gene expression involved in seed deterioration response under HTH stress, in this study, we conducted an RNA-Seq analysis using two previously screened soybean cultivars with contrasting seed deterioration resistance. HTH stress induced 1081 and 357 differentially expressed genes (DEGs) in the sensitive cultivar Ningzhen No. 1 and resistant cultivar Xiangdou No. 3, respectively. The majority of DEGs in the resistant cultivar were up-regulated, while down-regulated DEGs were predominant in the sensitive cultivar. KEGG pathway analysis revealed that metabolic pathways, biosynthesis of secondary metabolites, and protein processing in endoplasmic reticulum were the predominant pathways in both cultivars during seed deterioration under HTH stress. The genes involved in photosynthesis, carbohydrate metabolism, lipid metabolism, and heat shock proteins pathways might contribute to the different response to seed deterioration under HTH treatment in the two soybean cultivars. Our study extends the knowledge of gene expression in soybean seed under HTH stress and further provides insight into the molecular mechanism of seed deterioration as well as new strategies for breeding soybean with improved seed deterioration resistance. Key words: soybean, high temperature and humidity, RNA-Seq, pre-harvest seed deterioration. Avant la recolte, les graines de soja au champ sont sensibles a un stress cause par une temperature et une humidite elevees (HTH), ce qui peut entrainer une deterioration des grains en pre-recolte, laquelle diminue la qualite des grains, le rendement et la vigueur des graines. Pour comprendre les profils d'expression genique associes a cette deterioration en reponse au stress HTH, les auteurs ont realise une etude RNA-Seq sur deux cultivars prealablement identifies comme presentant une resistance contrastee a cette deterioration. Le stress HTH a permis d'identifier, respectivement, 1081 et 357 genes a expression differentielle (DEG) chez le cultivar sensible Ningzhen No. 1 et le cultivar resistant Xiangdou No. 3. La majorite des DEG chez le cultivar resistant etaient exprimes a la hausse, tandis que les genes moins fortement exprimes etaient predominants chez le cultivar sensible. Une analyse des sentiers KEGG a revele que les 'sentiers metaboliques', la 'biosynthese des metabolites secondaires' et la 'maturation des proteines dans le reticulum endoplasmique' etaient les sentiers predominants touches lors de la deterioration des graines soumis a un stress HTH. Les genes impliques dans la photosynthese, le metabolisme des hydrates de carbone, le metabolisme des lipides et les proteines de choc thermique pourraient contribuer a la reponse differente observee entre les deux cultivars soumis a un traitement de stress HTH. Cette etude accroit les connaissances sur l'expression genique chez les graines de soja en reponse au stress HTH et fournit un eclairage sur le mecanisme moleculaire de la deterioration des graines ainsi que sur de nouvelles strategies pour selectionner des sojas dotes d'une meilleure resistance a la deterioration des graines. [Traduit par la Redaction] Mots-cles : soja, temperature et humidite elevees, RNA-Seq, deterioration des graines en pre-recolte., Introduction Soybean seeds provide major sources of oil and protein globally for human consumption and animal feed (Saha and Sultana 2008). Seed quality is determined by its composition of protein, [...]

Synthyris bullii (Plantaginaceae; Besseya bullii-, kittentails) is a rare endemic of the Midwestern U.S.A. Although seed germination studies have been conducted for this species, limited information is available regarding seed viability after prolonged seed storage. The main goal of this study was to re-assess seed germinability of Synthyris bullii seeds collected from 2008 to 2011 across its range. Overall, we found regardless of seed age, locality (i.e., site and state), and maternal environment (i.e.. open, semi-shaded, and shaded) seeds are still viable. Although values were low for seed germination and seedling survivorship, the results of this study are encouraging and point to seed harvesting and storage as one way to preserve this species., Introduction Synthyris bullii (Plantaginaceae; Besseya bullir, kittentails) is a rare endemic perennial prairie-savanna species of the Midwestern U.S.A. and states listed across its range [Iowa, Illinois, Indiana, Michigan, Minnesota, Ohio [...]

Seed dormancy and germination have been studied in the genetic model Brachypodium species complex in cooler, moist higher latitudes. Studying environmental factors in arid mountains affecting dormancy and germination in Brachypodium complex could determine the factors controlling these processes. This study assesses the impacts of temperature during seed maturation, seed after-ripening, drought, photoperiod, and thermoperiod on final germination and germination rate index of B. hybridum in the Arabian Desert. Seeds were germinated under dark or light conditions and under different ratios of red:far-red light, with three diurnal thermoperiods. The final germination percentage was significantly greater at 15/25 [degrees]C and 20/30 [degrees]C than at 25/35 [degrees]C and in light rather than in darkness. Seeds that reached maturity at 15/25 [degrees]C attained greater germination rates and faster germination than those that reached maturity at 20/30 [degrees]C. One-year after-ripening enhanced the final germination percentage and reduced photoperiod requirements. Light quality did not affect final germination percentage. The seeds tolerated drought of up to -0.8 MPa polyethylene glycol. The tolerance of B. hybridum seeds produced at higher thermoperiods to moderate levels of osmotic stress and their higher dormancy indicate that this species has the potential to survive the projected global warming in its native and introduced ranges. Key words: after-ripening, dormancy, germination requirements, maternal thermoperiod, grasses. La dormance et la germination des graines ont ete etudiees dans le modele genetique offert par le complexe d'especes Brachypodium a des latitudes elevees, plus froides et humides. L'etude des facteurs environnementaux des montagnes arides qui affectent la dormance et la germination du complexe des Brachypodium pourrait permettre de determiner ceux qui controlent ces processus. Cette etude evalue les impacts de la temperature durant la maturation des graines, la post-maturation des graines, la secheresse, la photoperiode et la thermoperiode sur la germination finale et l'indice du taux de germination de B. hybridum dans le desert Arabique. Les graines ont germe a la noirceur et a la lumiere, et sous differents ratios de lumiere rouge : rouge lointain, selon trois photoperiodes diurnes. Le pourcentage final de germination etait significativement plus eleve a 15/25 [degrees]C et 20/30 [degrees]C qu'a 25/35 [degrees]C, et a la lumiere comparativement a la noirceur. Les graines qui atteignaient la maturite a 15/25[degrees] C germaient mieux et plus rapidement que celles qui atteignaient la maturite a 20/30 [degrees]C. Une post-maturation d'une annee accroissait le pourcentage final de germination et reduisait le besoin de photoperiode. La qualite de la lumiere n'affectait pas le pourcentage final de germination. Les graines toleraient la secheresse jusqu'a -0,8 MPa en polyethylene glycol. La tolerance des graines de B. hybridum obtenue a des thermoperiodes plus elevees, a des niveaux moderes de stress osmotique et leur dormance elevee indiquent que cette espece a le potentiel de survivre au rechauffement climatique planetaire anticipe dans les regions ou elle est indigene ou introduite. [Traduit par la Redaction] Mots-cles : post-maturation, dormance, conditions de germination, thermoperiode maternelle, herbes., Introduction Seed traits, such as dormancy and germination behavior, are important components that modulate plant fitness. These traits are regulated by the plants' genotype and the maternal environment (Luzuriaga et [...]

Like other outcrossing species, Scots pine (Pinus sylvestris L.) is thought to carry a 'genetic load' of deleterious recessive alleles. When these alleles occur as homozygotes in inbred progeny, their expression can give rise to 'inbreeding depression'. Although this phenomenon has been studied in several conifer species through selfing, few studies have quantified inbreeding depression in crosses with lower levels of relatedness between parents. We report here on the generation of a set of F3 study materials in Scots pine in which 142 families arose from a mating design among 49 F2 parents, representing nine levels of expected inbreeding coefficients between 0.0 and 0.5, and repeated over two consecutive seasons. Whereas the numbers of extractable seeds were unaffected by inbreeding, the proportion with fully developed embryos was strongly affected. This was expressed as inbreeding depression in the yield of full seeds per cone but not in their mean mass. Levels of germination of these full seeds were affected by inbreeding, but the depression was rather small and only weakly significant. The roles of pollen competition and polyembryony in mitigating the impact of inbreeding depression are discussed. The materials have been outplanted for future assessment of inbreeding depression on growth and survival. Key words: genetic load, inbreeding, inbreeding depression, Pinus sylvestris, tree breeding. Comme plusieurs especes a pollinisation croisee, le pin sylvestre (Pinus sylvestris L.) est repute etre porteur d'un <> cause par des alleles recessifs deleteres. Lorsque ces alleles se presentent sous la forme d'homozygotes chez la progeniture consanguine, leur expression peut donner lieu a ce que l'on appelle une << depression consanguine >>. Bien que ce phenomene ait ete etudie chez plusieurs especes de coniferes par autofecondation, peu d'etudes ont quantifie la depression consanguine chez des croisements presentant des niveaux d'apparentement plus faibles entre les parents. Cette etude porte sur la production d'un ensemble de descendants F3 chez le pin sylvestre, pour lequel 142 familles ont ete constituees a l'aide d'un plan de croisements impliquant 49 parents F2, representant neuf niveaux de consanguinite attendue entre 0,0 et 0,5. Les croisements ont ete repetes pendant deux saisons consecutives. Bien que le nombre de graines pouvant etre recuperees n'ait pas ete affecte, la consanguinite a fortement reduit la proportion d'embryons pleinement developpes. Cela s'est exprime comme une depression consanguine sur le rendement en graines pleines par cone, mais pas sur leur poids moyen. La germination de ces graines pleines a ete affectee par la consanguinite, mais la depression etait plutot faible et seulement faiblement significative. Les roles de la competition du pollen et de la polyembryonie dans l'attenuation de l'impact de la depression consanguine sont discutes. Le materiel issu des croisements a ete plante pour l'evaluation future de la depression consanguine sur la croissance et la survie. Mots-cles: fardeau genetique, consanguinite, depression consanguine, Pinus sylvestris, amelioration des arbres., 1. Introduction It is well known that the individuals of an outcrossing species typically carry a 'genetic load' of deleterious recessive alleles. In natural outbreeding populations, the excess frequency of [...]

Animal populations often decline due to habitat disturbance, but the initial response of organisms to human-induced environmental change is usually behavioral. Intra- and inter-specific interactions can restrict or facilitate access to resources, resulting in changes to individual fitness, and resource depletion may affect the frequency and strength of interactions. In birds, it is often assumed that feeding in groups increases foraging efficiency. We assessed how the reduction of seed resources provoked by cattle grazing affected different properties of seed-eating bird flocks in woodlands having the same structural characteristics but differing in seed abundance. Under lower availability of grass seeds (i.e., under grazing), flocks were smaller and less rich and birds showed a lower flocking propensity. This pattern could be explained by three non-exclusive hypotheses. Food reduction caused by grazing (i) decreases the number of seed-eating birds and concomitantly generates smaller flocks; (ii) reduces the density of nuclear species, decreasing the group cohesion in large flocks; (iii) makes large flocks less attractive by increasing individual competence for food. Our results provide evidence that cattle grazing affect the interactions of seed-eating birds and suggest the importance of understanding flocking behavior to bring about management actions. Key words: winter desert flocks, seed-eating birds, grazed woodland, flock structure, nuclear species. Si des declins de populations animales sont souvent causes par des perturbations de l'habitat, la reaction initiale des organismes a des changements induits par les humains est generalement de nature comportementale. Les interactions au sein d'especes et entre elles peuvent restreindre ou faciliter l'acces aux ressources, entraînant des modifications de l'aptitude des individus, et l'appauvrissement des ressources peut avoir une incidence sur la frequence et la force des interactions. Chez les oiseaux, il est souvent presume que l'alimentation en groupe accroît l'efficacite de la quete de nourriture. Nous avons evalue l'incidence de la reduction des ressources en graines provoquee par le paturage de betail sur differentes proprietes de groupes d'oiseaux granivores dans des zones boisees ayant les memes caracteristiques structurales, mais differentes abondances de graines. Dans des conditions de faible disponibilite de graines de graminees (c.-a-d., des conditions de paturage), les groupes d'oiseaux etaient plus petits et moins riches, et les oiseaux presentaient une plus faible propension a se regrouper. Cela pourrait s'expliquer par trois hypotheses non exclusives. La diminution de la nourriture causee par le paturage (i) reduit le nombre d'oiseaux granivores et, parallelement, produit de plus petits groupes, (ii) reduit la densite des especes nucleaires, reduisant du coup la cohesion des grands groupes, et (iii) fait en sorte que les grands groupes sont moins attrayants parce qu'ils accroissent la competition entre individus pour la nourriture. Nos resultats fournissent des preuves de l'incidence du paturage du betail sur les interactions d'oiseaux granivores et soulignent l'importance de comprendre le comportement de regroupement pour assurer l'efficacite des mesures de gestion. [Traduit par la Redaction] Mots-cles : groupes hivernaux du desert, oiseaux granivores, region boisee paturee, structure du groupe, espece nucleaire., Introduction Conservation biology is increasingly concerned with preserving interactions among species and individuals facing anthropogenic change (e.g., Bertiller et al. 2009; Valiente-Banuet et al. 2015; Zou et al. 2018). Bird [...]

Seed germination requirements for S. alata were investigated using cold stratification and phytohormones. Treatments included no stratification (control), two week, three week, four week, five week, and six week cold stratification. Hormone treatments included no stratification with cytokinin, no stratification with gibberellins, no stratification with cytokinin and gibberellins, no stratification with auxin, and one with six week stratification with abscisic acid. Three weeks cold stratification was required to yield a significant increase in percent germination. Gibberellin was the only hormone which caused a significant increase in germination in S. alata seeds. Keywords: abscisic acid, auxin, cytokinin, gibberellin, pitcher plant, Carnivorous plants have specialized traps to capture and digest animal prey for nutrient assimilation. Sarracenia alata, a pitcher plant native to regions in south eastern North America, including parts of [...]