The influence of the ectomycorrhizal fungus Rhizopogon subareolatus on growth and nutrient element localisation in two varieties of Douglas fir (Pseudotsuga menziesii var. menziesii and var. glauca) in response to manganese stress

Acidification of forest ecosystems leads to increased plant availability of the micronutrient manganese (Mn), which is toxic when taken up in excess. To investigate whether ectomycorrhizas protect against excessive Mn by improving plant growth and nutrition or by retention of excess Mn in the hyphal mantle, seedlings of two populations of Douglas fir (Pseudotsuga menziesii), two varieties, one being menziesii (DFM) and the other being glauca (DFG), were inoculated with the ectomycorrhizal fungus Rhizopogon subareolatus in sand cultures. Five months after inoculation, half of the inoculated and non-inoculated seedlings were exposed to excess Mn in the nutrient solution for further 5 months. At the end of this period, plant productivity, nutrient concentrations, Mn uptake and subcellular compartmentalisation were evaluated. Non-inoculated, non-stressed DFM plants produced about 2.5 times more biomass than similarly treated DFG. Excess Mn in the nutrient solution led to high accumulation of Mn in needles and roots but only to marginal loss in biomass. Colonisation with R. subareolatus slightly suppressed DFM growth but strongly reduced that of DFG (−50%) despite positive effects of mycorrhizas on plant phosphorus nutrition. Growth reductions of inoculated Douglas fir seedlings were unexpected since the degree of mycorrhization was not high, i.e. ca. 30% in DFM and 8% in DFG. Accumulation of high Mn was not prevented in inoculated seedlings. The hyphal mantle of mycorrhizal root tips accumulated divalent cations such as Ca, but not Mn, thus not providing a barrier against excessive Mn uptake into the plants associated with R. subareolatus

In vitro mycorrhization of micropropagated plants: studies on Castanea sativa Mill.

In vitro mycorrhization can be made by several axenic and nonaxenic techniques but criticism exists about their artificiality and inability to reproduce under natural conditions. However, artificial mycorrhization under controlled conditions can provide important information about the physiology of symbiosis. Micropropagated Castanea sativa plants were inoculated with the mycorrhizal fungus Pisolithus tinctorius after in vitro rooting. The mycorrhizal process was monitored at regular intervals in order to evaluate the mantle and hartig net formation, and the growth rates of mycorrhizal and nonmycorrhizal plants. Plant roots show fungal hyphae adhesion at the surface after 24 hours of mycorrhizal induction. After 20 days a mantle can be observed and a hartig net is forming although the morphology of the epidermal cells remains unaltered. At 30 days of root–fungus contact the hartig net is well developed and the epidermal cells are already enlarged. After 50 days of mycorrhizal induction, growth was higher for mycorrhizal plants than for nonmycorrhizal ones. The length of the major roots was lower in mycorrhizal plants after 40 days. Fresh and dry weights were higher in mycorrhizal plants after 30 days. The growth rates of chestnut mycorrhizal plants are in agreement with the morphological development of the mycorrhizal structures observed at each mycorrhizal time. The assessment of symbiotic establishment takes into account the formation of a mantle and a hartig net that were already developed at 30 days, when differences between fresh and dry weights of mycorrhizal and nonmycorrhizal plants can be quantified. In vitro conditions, mycorrhization influences plant physiology after 20 days of root–fungus contact, namely in terms of growth rates. Fresh and dry weights, heights, stem diameter and growth rates increased while major root growth rate decreased in mycorrhizal plants.Springe

Mycorrhizal synthesis between Pisolithus arhizus and adult clones of Arbutus unedo in vitro and in nursery

Arbutoid mycorrhizae were synthesized between adult selected clones of Arbutus unedo L. and Pisolithus arhizus. Two micropropagated clones were tested: AL1, in vitro and C1 (acclimatized plants) in nursery and later in a field trial. In vitro, rooted shoots were transferred to test tubes containing the substrate previously inoculated with mycelium cultured on agar. In the nursery, two inoculation treatments were tested (vegetative inocula or dry sporocarps) and compared to control plants. In the field trial, plants from nursery inoculation treatments were compared and an additional control treatment using seedlings was implemented. Plant height was evaluated 4 months later in the nursery and 20 months later in the field trial. Roots were examined by morphological and histological studies: a) in vitro plantlets one month after inoculation and nine months after acclimatization; and b) 20 months after the field trial was established. Arbutoid mycorrhizae were observed in vitro one month after inoculation, indicating compatibility between A. unedo and P. arhizus. These showed the presence of a mantle, Hartig net, and intracellular hyphal complexes confined to the epidermal root cells. Arbutoid mycorrhizae were also observed nine months after acclimatiza- Fund project: This work was supported by a PhD fellowship (SFRH/BD/37170/2007) from the Portuguese Foundation for Science and Technology (FCT) The online version is available at http://link.springer.com Filomena Gomes ( ) • Esteban San Martin Filomena Gomes. CERNAS, Dep. Recursos Florestais, Escola Superior Agrária Coimbra, Bencanta, 3040-316, Coimbra, Portugal, Tel: 351 239 802940, Fax: 351 239 802979, Email: [email protected] Helena Machado INIAV, Instituto Nacional de Investigação Agrária e Veterinária, IP., Av. República, Quinta do Marquês 2780-159 Oeiras, Portugal A. Portugal • Jorge M. Canhoto Centre of Functional Ecology, Department of Life Sciences, University of Coimbra, Ap. 3046, 3001-401 Coimbra, Portugal. Corresponding editor: Chai Ruihai tion in inoculated and control plants. In order to confirm the identity of mycorrhizae, molecular techniques were used, in previously inoculated in vitro plants, 12 months after acclimatization. Thelephora and Hebeloma mycorrhizae, two types of highly competitive and widespread mycorrhizae on nurseries were identified. In the nursery, dry sporocarp treatment improved plant height after four months. In a field trial (20 months later), plants growth did not show significant differences. By this time, mycorrhized roots with Cenococcum geophilum and other types were identified. These results and their implications on A. unedo breeding program are discussed.F. Gomes was supported by a PhD fellowship (SFRH/BD/37170/2007) from the Portuguese Foundation for Science and Technology (FCT)

The Development of Coordinated Communication in Infants at Heightened Risk for Autism Spectrum Disorder

This study evaluated the extent to which developmental change in coordination of social communication in early infancy differentiates children eventually diagnosed with ASD from those not likely to develop the disorder. A prospective longitudinal design was used to compare 9 infants at heightened risk for ASD (HR) later diagnosed with ASD, to 13 HR infants with language delay, 28 HR infants with no diagnosis, and 30 low risk infants. Hierarchical Linear Modeling (HLM) analyses revealed that ASD infants exhibited significantly slower growth in coordinations overall and in gestures coordinated with vocalizations, even relative to HR infants with language delay. Disruption in the development of gesture-vocalization coordinations may result in negative cascading effects that negatively impact later social and linguistic development