Gervais Rufyikiri

Uptake, Assimilation and Translocation of Mineral Elements in Monoxenic Cultivation Systems

While searching for optimal means to study the transport processes of nutrients and non-essential elements, diverse in vivo systems were developed using bi-compartmental containers where extraradical mycelium (ERM) of mycorrhizal fungi was separated from the plant roots. These systems generated some major results (reviewed in Smith and Read 1997), but suffered several limitations such as (1) the presence of undesirable micro-organisms which could influence element bioavailability or the transport processes; (2) the difficulty to visualize the ERM dynamic development and the bidirectional translocation processes in hyphae; (3) the difficulty to collect ERM and to distinguish thin hyphae of arbuscular mycorrhizal (AM) fungi from other fungi. As a consequence, some innovative approaches were tried out, such as the system of Pearson and Tinker (1975), used by Cooper and Tinker (1978) to study the transport of P, Zn and S by AM fungi. This system was based on a bi-compartment Petri plate in which a mycorrhizal plant (Trifolium repens L.) was grown on sterilized soil, while the ERM was allowed to cross the partition wall to develop in an agar medium without roots. This ingenious system kept the plant and the AM fungus (Glomus mosseae) under sterile conditions but, as the seedling developed, a hole was made in the lid and the plant grew out from it, making the system difficult to maintain free from other micro-organisms. This system was improved by St Arnaud et al. (1996), by growing the AM fungus in bi-compartmental Petri plates under monoxenic culture conditions on