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Enzymes in the Environment: Activity, Ecology and Applications - Chapter 5

Nấm trên mặt đất có thể áp dụng các chiến lược cuộc sống khác nhau để khai thác nguồn chất dinh dưỡng. Họ phát triển như saprotrophs trên chất nền hữu cơ đơn giản hay phức tạp, hoặc họ có thể thiết lập một mối quan hệ dinh dưỡng với các nhà máy cao hơn, hoặc như là biotrophs hoặc như necrotrophs. Các hiệp hội rễ tương tác quan trọng nhất biotrophic hỗ sinh giữa (1). Hơn 80% thực vật có hoa mạch máu có khả năng tham gia vào các hiệp hội cộng sinh với nấm arbuscular mycorrhizal (AM). | 5 Enzymes in the Arbuscular Mycorrhizal Symbiosis Jose Manuel Garcia-Garrido Juan Antonio Ocampo and Inmaculada Garcia-Romera Estacion Experimental del Zaidin CSIC Granada Spain I. INTRODUCTION Terrestrial fungi can adopt different life strategies to exploit nutrient sources. They grow as saprotrophs on simple or complex organic substrates or they can establish a nutritional relationship with higher plants either as biotrophs or as necrotrophs. Mycorrhizal associations are the most important mutualistic biotrophic interactions 1 . Over 80 of vascular flowering plants are capable of entering into symbiotic associations with arbuscular mycorrhizal AM fungi 2 . The fungi that form these associations are members of the zygomycetes and the current classification places them all into one order Glomales 3 . They are strictly dependent on their host plant to complete their life cycle whereas other mycorrhizal fungi such as ericoid fungi can be grown in pure culture 4-6 . The AM association is a relatively nonspecific highly compatible long-lasting mutuality from which both partners derive benefit. The plant supplies the fungus with carbon on which it is entirely dependent. The fungal contribution is more complex. Although it is clear that the fungi assist the plant with the acquisition of phosphate and other mineral nutrients from the soil AM fungi also may influence the plant s resistance to invading pathogens 7 . In addition to its ecological significance the association also may have applications in agriculture. This is particularly important for developing more sustainable systems 8 because mycorrhizae create an intimate link between the soil and the plant and may be manipulated to improve plant nutrition efficiency and soil conservation. The interaction begins when fungal hyphae arising from spores in the soil and on adjacent colonized roots or hyphae contact the root surface. Here they differentiate to form appressoria and penetrate the root. The formation of .