الصفحة 1
الصفحة 1
Mycorrhizae : Sustainable Agriculture and Forestry
This book discusses and goes into detail on a number of topics: the molecular basis of nutrient exchange between arbuscular mycorrhizal (AM) fungi and host plants; the role of AM fungi in disease protection, alleviation of soil stresses and increasing grain production; interactions of AM fungi and beneficial saprophytic mycoflora in terms of plant growth promotion; the role of AM fungi in the restoration of native ecosystems; indirect contributions of AM fungi and soil aggregation to plant growth and mycorrhizosphere effect of multitrophic interaction; the mechanisms by which mycorrhizas change a disturbed ecosystem into productive land; the importance of reinstallation of mycorrhizal systems in the rhizosphere is emphasized and their impact on landscape regeneration, and in bioremediation of contaminated soils; Ectomycorrhizae (ECM) and their importance in forest ecosystems and associations of ECM in tropical rain forests function to maintain tropical monodominance; in vitro mycorrhization of micro-propagated plants, and visualizing and quantifying endorhizal fungi; the use of mycorrhizae, mainly AM and ECM, for sustainable agriculture and forestry.
Microorganisms in soils : Roles in genesis and functions
The following key topics are covered: Microorganisms in bioerosion, humification, mineralization and soil aggregation; Microbial energetics and microbes in biogeochemical processes such as carbon and nitrogen cycles and phosphorus bio-availability; Interactions in the mycorrhizosphere, e.g. between mycorrhizal fungi and bacteria; Impact of microbes on plant nutrient cycling and the possible effects of transgenic rhizospheres on soil fungi; Functions of microbes in specific soil compartments such as soil surface or toxic metal polluted soils; Regulation of microbial activities in functional domains that are influenced by biotic or abiotic factors; Use of marker genes and isotopes as examples for modern techniques in soil microbiology.
Microbial Activity in the Rhizosphere
The rhizosphere is a very complex environment in which the effects of the plant on soil microorganisms and the effects of the microorganisms on the plant are interacting and are interdependent. Plant root exudates and breakdown products attract microbes and feed them and, in turn, the plants often benefit from the microbes. Interactions among microorganisms and plant roots are essential for nutritional requirements of the plant. Plant growth, development and productivity are largely dependent on the soil environment in the root region rhizosphere. The new techniques of studying the rhizosphere enables us to get a much better understanding of the dynamics of the rhizosphere population, such rhizosphere studies being of interest to agriculturists, soilbiologists, chemists, microbiologists and molecular biologists. The rhizosphere microbes in?uence the root environment in several ways. They may change the oxidation-reduction potential, influence the availability of moisture and nutrients, produce growth inhibiting or growth promoting substances in the form of exudates, provide competition and possibly induce many other effects. My corrhizal associations are beneficial in mineral uptake and in increasing root surface area for effective ion absorption. Antagonism, ompetition and synergism in soil and the rhizoplane (rhizosphere) are the most important microbial interactions to consider in the study of rhizosphere biology. With the growing information on the production of growth regulators, competitiveness of the microbes in the rhizosphere, microsymbionts, and other factors, their effect upon plant growth will become more evident. Experiments on the introduction of microbes or their products in the rhizosphere will help to improve our understandingofthebiologyoftherhizosphere.
