Éléments de philosophie scientifique : à l'usage des élèves de mathématiques, de philosophie et des candidats à Saint-Cyr / par Pierre-F. Pécaut,...

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Pollinisation de l'artichaut (Cynara scolymus L.) par l'abeille domestique (Apis mellifera L.) en production de semences hybrides sous abris grillagés

Pollination of globe artichoke (Cynara scolymus L.) by honey bees (Apis mellifera L.) to produce hybrid seed under enclosure. Globe artichoke is currently multiplied mainly by vegetative means, but the planting of seeds could lead to easier cropping practices and improved yields. This is especially true with hybrid seeds which could be produced using the two genetic male-sterility systems available. For two years, we studied the effectiveness of honey bees as pollinators to produce hybrid seeds of globe artichoke under insect-proof enclosures. We used two adjacent $10 \times 6$ m tunnels covered with 1-mm mesh screen and planted with 2 male-fertile (MF) and 7 male-sterile (MS) lines (tab. I). Each tunnel was provided with a colony of 3,500 bees at the onset of MF flowering. Flowering of MS and MF lines was well synchronized (fig. 1), and the number of flower heads per plant was similar for all lines. Yet, there were over 10-fold differences in both years in the density of foragers that visited the various lines with extremes of 0.04 to 1.18 honey bees per head (fig. 2). Some foragers collected pollen, but these were rarely seen on MS heads. The ranking of MS lines in terms of forager density was similar over both seasons, which suggests that the differences in attractiveness among these lines were of genetic origin and probably resulted from differences in nectar availability or composition. Yield of achenes per plant also varied significantly among lines (fig. 3). The proportion of heads that were empty ranged from 23% to 100% among MS lines, and for each season was negatively correlated with the average forager density on each line (fig. 4). The number of achenes per head in the flower heads which were not empty did not vary significantly among MS lines (tab. II), which suggests that the pollination effectiveness of honey bee visits was similar among these different lines. This achene content was greater in MF heads, which is consistent with a greater pollination effectiveness of honey bees in this inflorescence due to the presence of pollen and some self-fertility in MF lines. The overall forager density was similar between the two seasons as was the proportion of empty MS heads, but the achene content of non-empty MS heads was significantly greater in the second year than in the first one (tab. II). This suggests that the pollination effectiveness of individual visits was greater in the second year. Pollen availability was similar in both seasons, but there were 5 times fewer foragers collecting pollen in the second year compared to the first one. The pool of pollen is limited when producing hybrid seed, especially in confined environments, and our results suggest that in these situations the level of pollen collection may negatively affect the pollination activity of honey bee colonies.On a étudié le butinage des abeilles domestiques (Apis mellifera) et leur efficacité pollinisatrice avec 2 lignées mâle fertiles (MF) et 7 lignées mâle stériles (MS) d'artichaut (Cynara scolymus) sous cages " insectproof "pendant 2 ans. Les floraisons MF et MS étaient synchrones et la floribondité de toutes les lignées était comparable. Néanmoins, les densités de butineuses ont varié selon les lignées avec des extrêmes allant de 0,04 à 1,18 abeilles par capitule et le classement des lignées était similaire lors des 2 années. La proportion de capitules MS sans akène a varié de 23 à 100 % et elle était corrélée négativement avec la densité de butineuses, ce qui souligne l'importance de l'attractivité des lignées MS pour leur pollinisation. Le nombre d'akènes des capitules pourvus d'akènes était plus élevé pour les lignées MF que MS, mais il était uniforme pour toutes les lignées MS à chaque saison, ce qui suggère que l'efficacité pollinisatrice des visites d'abeilles était constante sur ces lignées

Pollinisation de l'artichaut (Cynara scolymus L.) par l'abeille domestique (Apis mellifera L.) en production de semences hybrides sous abris grillagés

Pollination of globe artichoke (Cynara scolymus L.) by honey bees (Apis mellifera L.) to produce hybrid seed under enclosure. Globe artichoke is currently multiplied mainly by vegetative means, but the planting of seeds could lead to easier cropping practices and improved yields. This is especially true with hybrid seeds which could be produced using the two genetic male-sterility systems available. For two years, we studied the effectiveness of honey bees as pollinators to produce hybrid seeds of globe artichoke under insect-proof enclosures. We used two adjacent $10 \times 6$ m tunnels covered with 1-mm mesh screen and planted with 2 male-fertile (MF) and 7 male-sterile (MS) lines (tab. I). Each tunnel was provided with a colony of 3,500 bees at the onset of MF flowering. Flowering of MS and MF lines was well synchronized (fig. 1), and the number of flower heads per plant was similar for all lines. Yet, there were over 10-fold differences in both years in the density of foragers that visited the various lines with extremes of 0.04 to 1.18 honey bees per head (fig. 2). Some foragers collected pollen, but these were rarely seen on MS heads. The ranking of MS lines in terms of forager density was similar over both seasons, which suggests that the differences in attractiveness among these lines were of genetic origin and probably resulted from differences in nectar availability or composition. Yield of achenes per plant also varied significantly among lines (fig. 3). The proportion of heads that were empty ranged from 23% to 100% among MS lines, and for each season was negatively correlated with the average forager density on each line (fig. 4). The number of achenes per head in the flower heads which were not empty did not vary significantly among MS lines (tab. II), which suggests that the pollination effectiveness of honey bee visits was similar among these different lines. This achene content was greater in MF heads, which is consistent with a greater pollination effectiveness of honey bees in this inflorescence due to the presence of pollen and some self-fertility in MF lines. The overall forager density was similar between the two seasons as was the proportion of empty MS heads, but the achene content of non-empty MS heads was significantly greater in the second year than in the first one (tab. II). This suggests that the pollination effectiveness of individual visits was greater in the second year. Pollen availability was similar in both seasons, but there were 5 times fewer foragers collecting pollen in the second year compared to the first one. The pool of pollen is limited when producing hybrid seed, especially in confined environments, and our results suggest that in these situations the level of pollen collection may negatively affect the pollination activity of honey bee colonies.On a étudié le butinage des abeilles domestiques (Apis mellifera) et leur efficacité pollinisatrice avec 2 lignées mâle fertiles (MF) et 7 lignées mâle stériles (MS) d'artichaut (Cynara scolymus) sous cages " insectproof "pendant 2 ans. Les floraisons MF et MS étaient synchrones et la floribondité de toutes les lignées était comparable. Néanmoins, les densités de butineuses ont varié selon les lignées avec des extrêmes allant de 0,04 à 1,18 abeilles par capitule et le classement des lignées était similaire lors des 2 années. La proportion de capitules MS sans akène a varié de 23 à 100 % et elle était corrélée négativement avec la densité de butineuses, ce qui souligne l'importance de l'attractivité des lignées MS pour leur pollinisation. Le nombre d'akènes des capitules pourvus d'akènes était plus élevé pour les lignées MF que MS, mais il était uniforme pour toutes les lignées MS à chaque saison, ce qui suggère que l'efficacité pollinisatrice des visites d'abeilles était constante sur ces lignées

Lanthanide(III) complexation by the ligand 1,3,5-triamino-1,3,5-trideoxy-cis-inositol: an unusual thermodynamic behaviour across the rare-earth series.

International audienc

Revisiting doping mechanisms of n-type organic materials with N-DMBI for thermoelectric applications: Photo-activation, thermal activation, and air stability

International audienceUnderstanding doping mechanisms is essential for optimizing the doping efficiency and rationally designing next generations of dopants and organic materials. Over the last years, N-DMBI became a reference solution-processed n-type dopant, affording decent air-stability and record power factor for thermoelectric energy generation. Nevertheless, a complet