Ascophyllum nodosum extracts (ANE) are well-established plant biostimulants that improve stress tolerance and crop vigour, while also having been shown to stimulate soil microbes. The intersection of these two stimulatory activities, and how they combine to enhance plant health, however, remains poorly understood. In the present study, we aimed to evaluate: (1) the direct effect of ANE on the arbuscular mycorrhizal fungus Rhizophagus irregularis, and (2) whether ANE influences endomycorrhization in plants. ANE enhanced development of R. irregularis in vitro, showing greater spore germination, germ tube length, and hyphal branching. Greenhouse-grown Medicago truncatula drench-treated with ANE formed mycorrhizal associations faster (3.1-fold higher mycorrhization at week 4) and grew larger (29% greater leaf area by week 8) than control plants. Foliar applications of ANE also increased root colonization and arbuscular maturity, but did not appear to enhance plant growth. Nonetheless, following either foliar or drench application, M. truncatula genes associated with establishment of mycorrhizae were expressed at significantly higher levels compared to controls. These results suggest that ANE enhances mycorrhization through both direct stimulation of arbuscular mycorrhizal fungus growth and through stimulation of the plant’s accommodation of the symbiont, together promoting the establishment of this agriculturally vital plant–microbe symbiosis.

. 2002. Timing, magnitude and causes of flower and immature fruit loss in pin cherry and choke cherry. Can. J. Plant Sci. 82: 157-164. Pin cherry (Prunus pensylvanica L.) and choke cherry (Prunus virginiana L.) are two wild fruit species with potential for commercial production, but information about fruit production is limited. The objectives of this study were to determine, for both species, the timing and magnitude of flower and immature fruit loss, and to determine the primary causes of this loss, including the effects of pollen source and supplemental pollination. Sequential sampling of both pin cherry and choke cherry indicated that the primary period of abscission occurred during the first 3 wk following full bloom. Final fruit set ranged from 32.6 to 44.7% of flower number for pin cherry, and from 3.7 to 20.1% for choke cherry. Insect damage accounted for only 14% of the total observed flower and fruit abscissions in pin cherry and 7% in choke cherry. The major insect pest causing this loss in pin cherry was a sawfly (Hoplocampa sp., Tenthredinidae) and in choke cherry, a leafroller (Archips argyrospila, Tortricidae). A controlled pollination experiment was used to determine the effects of pollen source and supplemental pollination on pin cherry and choke cherry. Final fruit set for flowers that were cross-pollinated by hand in both pin cherry (mean of 51.3%) and choke cherry (mean of 56.9%) in most cases was significantly greater than flowers that were openpollinated, self-pollinated, or not pollinated. These data suggested that the majority of flower and immature fruit loss in both pin cherry and choke cherry resulted from a lack of pollination and/or fertilization. Les dommages attribuables aux insectes n'expliquent que 14 % des abscissions chez le cerisier de Pennsylvanie et 7 % chez le cerisier de Virginie. Le principal ravageur de la première espèce est un tenthrède (Hoplocampa sp., Tenthrénidés) tandis que chez la seconde, il s'agit d'une tordeuse de la feuille (Archips argyrospila, Tortricidés). Les auteurs ont effectué un essai de pollinisation contrôlée afin de déterminer les effets de l'origine du pollen et ont procédé à une sur-pollinisation chez les deux sortes d'arbre. Dans la plupart des cas, la nouaison est sensiblement plus importante (moyenne de 51,3 % pour le cerisier de Pennsylvanie et de 56,9 % pour le cerisier de Virginie) quand les fleurs sont fécondées à la main plutôt que lorsqu'il y a pollinisation libre, auto-pollinisation ou absence de pollinisation. Les données laissent croire que la chute des fleurs et des fruits immatures chez les deux espèces résulte surtout de l'absence de pollinisation et/ou de fécondation.Mots clés: Cerisier de Virginie, cerisier de Pennsylvanie, chute des fleurs, chute des fruits immatures, pollinisation, dommages dus aux insectesPrunus pensylvanica, pin cherry, and Prunus virginiana, choke cherry, are native fruit species occurring in abundance across Canada and the northern United States. The fruit of both species can be used to make jams, jellies, w...