The hidden world within plants: ecological and evolutionary considerations for defining functioning of microbial endophytes

All plants are inhabited internally by diverse microbial communities comprising bacterial, archaeal, fungal, and protistic taxa. These microorganisms showing endophytic lifestyles play crucial roles in plant development, growth, fitness, and diversification. The increasing awareness of and information on endophytes provide insight into the complexity of the plant microbiome. The nature of plant-endophyte interactions ranges from mutualism to pathogenicity. This depends on a set of abiotic and biotic factors, including the genotypes of plants and microbes, environmental conditions, and the dynamic network of interactions within the plant biome. In this review, we address the concept of endophytism, considering the latest insights into evolution, plant ecosystem functioning, and multipartite interactions.EU Cost Action [FA1103, 312117]; FWF (Austrian Science Foundation) [P26203-B22, P24569-B25]; Portuguese FCT (Foundation for Science and Technology) [SFRH/BPD/78931/2011]info:eu-repo/semantics/publishedVersio

Growth and root morphology of planted and naturally-regenerated Douglas fir and Lodgepole pine

Root system morphology and growth of Douglas fir (Pseudotsuga menziesii var glauca (Beissn) Franco) and Lodgepole pine (Pinus contorta var latifolia Engelm) saplings transplanted from containers to the field in 1979 were compared with naturally-regenerated saplings of the same species and age. Naturally-regenerated saplings of both species were significantly taller than planted trees, had greater leader growth in the previous year and height/diameter ratios, and smaller taproot diameters 10 cm below groundline. Naturally-regenerated saplings also had up to 2.3-fold the number of lateral roots compared with planted saplings. Seventy to 79% of all primary lateral roots of naturally-regenerated saplings occurred within the top 10 cm of the soil surface, compared with 30-42% for the planted trees. The depth of the first structural lateral root associated with naturally-regenerated saplings was also significantly less than that of planted saplings. The shape of the container in which seedlings were raised in the nursery was clearly evident when root system architecture of planted saplings was examined. Many container-initiated seedling root systems exhibited conical shaping with little lateral root egress. A variety of root deformities which included constriction, coiling and kinkiness were detected in planted, but not naturally-regenerated saplings. These results are discussed in relation to potential difficulties arising from artificial forest regeneration with pine and Douglas fir.Croissance et morphologie des systèmes racinaires de douglas et de pins de Murray élevés en conteneurs. La morphologie du système racinaire et la croissance de plants de douglas (Pseudotsuga menziesii var glauca (Beissn) Franco) et de pin de Murray (Pinus contorta var latifolia Engelm) éduqués en conteneurs et installés sur le terrain en 1979 ont été comparées avec celles de semis naturels de même essence et de même âge. Les semis naturels sont significativement plus grands et ont une dernière pousse plus importante. Le diamètre du pivot mesuré à 10 cm sous le niveau du sol est plus petit; ils possèdent 2,3 fois plus de racines latérales que les plants élevés en conteneurs; 70 à 79% de leurs racines principales se développent dans les 10 premiers centimètres du sol, contre 30 à 42% pour les plants élevés en conteneurs. La profondeur d'apparition des premières racines latérales est également plus faible. Chez les plants élevés en conteneurs, la forme de ce conteneur reste visible lors de l'examen de l'architecture du système racinaire. Un certain nombre de déformations (resserrements, enroulements, nœuds) visibles chez les plants produits en conteneurs sont absents chez les semis naturels. Ces résultats sont discutés en relation avec les problèmes susceptibles de se produire dans le cas de régénération artificielle des pins et du douglas