Induced defenses of loblolly pine, Pinus taeda: potential impact on Dendroctonus frontalis within-tree mortality

Loblolly pine (Pinus taeda L.) produces an induced defensive hypersensitive response in inner bark colonized by the southern pine beetle, Dendroctonus frontalis Zimm. (Coleoptera: Scolytidae), and its associated fungi. Adult beetles forced to colonize the induced response tissue in a laboratory study constructed galleries that were the same length as adults boring in normal phloem. However, each female laid fewer eggs in the induced tissue. Larval and pupal mortality were also higher in this tissue when compared to surrounding phloem. Beetles colonizing trees in response to pheromone baits constructed less gallery and laid fewer eggs in induced tissue than in surrounding normal phloem. These results suggest that the lesions produced by the induced defense system in conifers may not only contain the growth of fungi inoculated into trees during the attack phase of beetle colonization, but may also affect survival of bark beetle progeny.

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Résumé Une réaction hypersensible de défense a été induite dans les couches profondes de l'écorce de P. taeda colonisée par D. frontalis et le champignon qui lui est associé. Au laboratoire, des adultes, contraints de coloniser les tissus où une réaction hypersensible e été induite, ont foré des galeries de même longueur que celles creusées dans du phloème sain. Cependant les femelles ont pondu moins d'oeufs dans les tissus induits; les mortalités larvaires et nymphales étaient aussi plus fortes dans ce tissu que dans le phloème voisin. Les scolytes, ayant colonisé les arbres après attraction par des pièges à phéromones, forent moins de galeries et pondent moins d'oeufs dans le tissu induit que dans le phloème sain voisin. Ces résultats suggèrent que les lésions, provoquées par le système de défense induit des conifères, peuvent non seulement limiter la croissance du champignon inoculé dans l'arbre au cours de la colonisation des scolytes, mais aussi affecter la survie des descendants dans l'écorce.

     

Evolution of the glycogen content and of glucose-6-phosphatase activity in the liver of Salmo gairdneri during development.

The evolution of the liver's glycogenic content, cytochemical characterization of the glycogen and glucose-6-phosphatase activity enable us to define three successive phases up to stage 36, just before the first feed. The grade which was low up to stage 24 is then due to beta-particles of ovule origin. Then, up to stage 27, there is a storage phase: alpha-particles appear and accumulate while the enzymatic activity remains non-existent. From the stage 28 to 36 the grade is progressively increasing, the enzymatic activity appears and increases. When the phase ends the liver is able to ensure glycemic regulation and to deal with exogenous nutritional contributions.     

Electron Microscopy of Pseudomonas φ6 Bacteriophage

phi6 bacteriophage from Pseudomonas phaseolicola has a pleomorphic shape due to an outer layer of lipid. This layer was removed with organic solvents or sodium dodecyl sulfate revealing a 50-nm cubic particle. The virus was found only in the central portion of the cell and not near the cell wall.