Effects of endomycorrhizal development and light regimes on the growth of Dicorynia guianensis Amshoff seedlings

Abstract

-The influence of mycorrhizal infection rate and light environment on growth traits was examined for 50-week-old Dicorynia guianensis Amshoff tree seedlings. The seedlings were grown on two soil substrates (control and inoculated) in shade tunnels under three relative light levels (50%, 14% and 1% of full sunshine). For seedlings growing under 1% of full sunlight no significant differences between control and inoculated plants were observed in plant traits though a high rate of endomycorrhizal infection was recorded. In partial shaded sunlight, 14% and 50%, the rate of mycorrhizal infection was positively related to the growth performances of seedlings. The optimal growth was obtained under 14% of full sunlight, showing a greater efficiency of the mycorrhizas. tropical rainforest / Dicorynia guianensis / seedlings / endomycorrhizas / light / experimental approach Résumé -Effet des mycorhizes et de la lumière sur la croissance des semis de Dicorynia guianensis Amshoff, une césalpinia-cée de la forêt tropicale humide de Guyane française. Des semis de D. guianensis ont été cultivés en pots sur un sol désinfecté, inoculé ou non avec du sol forestier, dans des serres tunnels sous trois régimes lumineux (1 %, 14 %, 50 % du plein découvert). Des paramètres de croissance des plants et la colonisation endomycorhizienne des racines ont été mesurés au bout de 50 semaines. Les semis soumis à 1% d'éclairement et croissant sur les deux types de sol ne présentaient aucune différence significative pour aucun des caractères mesurés, bien qu'un taux élevé de mycorhization aie été noté chez les plants sur sol inoculé. En éclairement partiel, 14 et 50 %, les performances de croissance des semis étaient positivement reliées au taux d'infection mycorhizienne. L'optimum de croissance était obtenu pour l'intensité lumineuse moyenne (14 %), montrant ainsi une meilleure efficacité des mycorhizes.forêt tropicale humide / Dicorynia guianensis / semis / endomycorhizes / lumière / approche expérimentale

How does light and phosphorus fertilisation affect the growth and ectomycorrhizal community of two contrasting dipterocarp species?

“…A number of other studies with dipterocarp species have found that, this is indeed the case, with seedlings grown in the understorey having a lower level of EcM colonisation than those in canopy gaps (Becker 1983;Ingleby et al 1998). It appears that the highest levels of mycorrhizal colonisation occur under the light levels where the greatest growth, and hence carbon fixation, of the host plant is found (Prajadinata and Santoso 1993; Béreau et al 2000). However, many EcM fungi are capable of a certain amount of saprotrophic growth and may not, therefore, be totally reliant upon plant carbohydrates leading to the lack of effect of the light conditions on EcM colonisation in this present study.…”

The effect of plant light environment on mycorrhizal colonisation in field‐grown seedlings of podocarp‐angiosperm forest tree species

“…However, Johnson (1976) observed no decrease in colonisation when the light demanding species Leptospermum scoparium and Coprosma robusta were heavily shaded. In another glasshouse study, Bereau et al (2000) found high levels of colonisation in heavily shaded seedlings of the tropical forest tree Dicorynia guianensis. There have been few studies that have investigated the mycorrhizal colonisation of field-grown seedlings of the same species in different light environments.…”

Phosphorus limitation, soil‐borne pathogens and the coexistence of plant species in hyperdiverse forests and shrublands

“…Tropical rainforest tree seedlings are much more likely to succumb to damping-off pathogens in the shade than in light gaps, especially near conspecific mature trees (Augspurger, 1984;Hood et al, 2004), and susceptibility to pathogens is greater for less shade-tolerant species (McCarthy-Neumann & Kobe, 2008). Moreover, seedlings often show reduced AM colonization and are generally less responsive (in terms of growth) to AM colonization at low irradiance (Bereau et al, 2000;Gehring, 2003). AM fungi can even reduce seedling survival and growth of shade-tolerant tropical tree species (McCarthy-Neumann & Kobe, 2008).…”