| Rhizobia, the root-nodule endosymbionts of leguminous plants, also form natural endophytic associations with roots of important cereal plants. Regardless this association occurs widely,much remains unknown about rhizobial colonization to cereals and molecular interaction between them. In this study, we applied a multidisciplinary approach including microscopy (LCSM), molecular techniques and proteomics to explore the mechanism of plant growth promotion from their interaction.We inoculated rice, tobacco and legumes of alfalfa, sesbania etc. with four species of gfp-tagged rhizobia using LCSM combined with viable plating experiments to examine their infection, dissemination, and colonization in these plant tissues, and their influence on the growth physiology of plants. The results are indicated as follows:1. The infection of rhizobia to rice was a dynamic process beginning with surface colonization of the rhizoplane (especially at lateral root emergence), followed by endophytic colonization within roots, and then ascending endophytic migration into the stem base, leaf sheath, and leaves where they developed high populations. Rice plants inoculated with certain test strains of gfp-tagged rhizobia produced significantly higher root and shoot biomass; increased their photosynthetic rate, stomatal conductance, transpiration velocity, water utilization efficiency, and flag leaf area (considered to possess the highest photosynthetic activity); and accumulated higher levels of indoleacetic acid and gibberellin growth regulating phytohormones.2. Rhizobia could perform a dynamic colonization process in both below-ground and above-ground tissues of tobacco plants via two routes: internal movement and surface movement, and made alternating epiphytic–endophytic– epiphytic lifestyles: Rhizobia entry into root and growth within the root interior, followed by ascending endophytic migration within stems up into leaf tissues, and finally exiting through...
|
PDF Full Text Request