Lecture notes 13

Plants of family monotropaceae lack chlorophyll

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Unformatted text preview: pacridaceae •  Both families produce coils of hyphae termed “hair roots” •  Fungi that produce this mycorrhiza are free ­ living saprotrophs in soil –  Ascomycota Fig. 13.10. Sec8on through part of the protocorm (basal stem region) of an orchid, Neo4a, showing coils of hyphae (termed 'peletons') within the orchid cells.The plant cells were alive at the 8me of sec8oning, evidenced by presence of nuclei (the dark granular structures) in two of the orchid cells. [� Jim Deacon] Ericoid Mycorrhizas •  Grown in culture –  Produce septate hyphae with fragmented zigzag growth •  Primary role –  To provide host plants with nitrogen •  Secrete proteinase –  Release amino acids from soil organic mafer Orchid Mycorrhizas •  Parasi8c on fungus •  Orchid seeds –  Small, consists of embryo and few nutrient reserves –  Triggered to germinate •  Produce few root hairs •  Must be colonized by a fungus at an early stage or seedling will die 4 11/23/09 Orchid Mycorrhizas •  Fungus penetrates orchid embryo and produces hyphal coils –  Peletons •  Only last a few days •  Degenerate and replaced by further coils in other cells •  Repeated process provides main source of sugar to developing orchid Monotropoid Mycorrhizas •  Plants of family Monotropaceae lack chlorophyll –  Dependent on mycorrhiza fungi for all their nutrients •  Found in shade beneath forest trees •  Fungi involved are Basidiomycota Orchid Mycorrhizas •  Provide orchids with sole source of carbohydrates during early years of life –  Most do not emerge above ground or produce chlorophyll un8l 3 ­5 years old –  As many as 200 species never...
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