Ecophysiology and Seedlings Nutrient Contents of Forest Species Ricinodendron heudelotii (Mull. Arg.) and Cola acuminata (P. Beauv.) Influenced by Biofertilizer and Salinity

Abstract

Ricinodendron heudelotii and Cola acuminata, are important plants species whose exploitation became abusive over the years due to the high utilization of their fruits as Non-Timber Forest Products (NTFP). They face to multiple challenges: a recalcitrance of seeds and salinity that limits regeneration. Therefore, regeneration seems an appropriate corridor for domestication with the optimization of plant mycorrhizal symbiosis otherwise called arbuscular mycorrhizal fungi (AMF). But alongside this domestication can be added constraints due to salinity of the soils in coastal region. This justify the aim of this work which was to study dynamics and evaluate the effect of salinity and mycorrhizal biofertilizers on the Ricinodendron heudelotii and Cola acuminata seedlings. To undergo this purpose, data were collected in two villages (Kendje and Njombeng) in Mungo division, and assay were conducted in greenhouse at the Faculty of Science, University of Douala-Cameroon. In the field, the identification of species was assessed over an area of 1600 m² as well as the circumference of the trees, the individual number of Ricinodendron heudelotii and Cola acuminata among other species in order to assess their maturity and rarity in the forest. The second part was carried out in the greenhouse for the purpose of germination, obtaining seedlings and evaluating the effects of arbuscular mycorrhizal fungi (Gisgaspora margarita) as biofertilizers on the seedlings in saline conditions (0, 50, 100 and 200 mM of NaCl). Some parameters were determined on seedlings (plant growth, dry weight, distribution of ions in plant organs, chlorophyll and carotenoid content) over a period of twenty-six weeks. Globally Cola acuminata is more present in the forest (5.88%) than Ricinodendron heudelotii (1.47%) with average circumference of 105cm for both species. AMF-biofertilizer alleviates the deleterious effect of salt stress on plants growth parameters depending of concentration. Moreover, for those species, the distribution of Na⁺ is more accumulated in the root’s plants unlike K⁺ and P which are more concentrated in the leaves.