使用者:Xht88114/沙盒

Epacris pulchella，一種產於東澳的杜鵑花科植物。

長柱杜鵑(Rhododendron occidentale)是一種產於北美西方的杜鵑花菌根共生植物。

杜鵑花菌根是一類和杜鵑花科植物共生的菌根真菌，杜鵑花科植物通常生活在北方針葉林、沼澤和石楠荒原等酸性貧脊的土壤，因此這種共生關係對杜鵑花科植物適應環境十分重要。經過分子鐘技術推定這種共生關係大約起源於1.4億年前。

構造和功能

杜鵑花菌根能在杜鵑花科植物的髮根上形成疏鬆的菌根包附在表皮細胞上，, 穿入皮層細胞的細胞壁並在細胞間產生菌絲圈來將細胞緊緊包附。Ericoid mycorrhizas are characterized by fungal coils that form in the epidermal cells of the fine hair roots of ericaceous species. Ericoid mycorrhizal fungi establish loose hyphal networks around the outside of hair rootsfrom which they penetrate the walls of cortical cells to form intracellular coils that can densely pack individual plant cells. 但並不穿入細胞膜However, the fungi do not penetrate plasma membranes of plant cells. 這種構造只能持續幾周，不久後便會崩壞分解。Evidence suggests that coils only function for a period of a few weeks before the plant cell and fungal hyphae begin to degrade.

菌絲圈是真菌用來交換來自土壤的養分和植物光合作用的醣類The coil is the site where fungi exchange nutrients obtained from the soil for carbohydrates fixed through photosynthesis by the plant. 有產生酵素來分解複雜有機物的能力Ericoid mycorrhizal fungi have been shown to have enzymatic capabilities to break down complex organic molecules. 這讓一些蘭花菌根能進行腐生This may allow some ericoid mycorrhizal fungi to act as saprotrophs. 最初的功能是取得有機形式的營養，例如氮，However, the primary function of these enzymatic capabilities is likely to access organic forms of nutrients, such as nitrogen, whose mineralized forms are in very limiting quantities in habitats typically occupied by ericaceous plants.

真菌共生體

從Woollsia pungens分離的杜鵑花菌根Gamarada debralockiae。

The majority of research with ericoid mycorrhizal fungal physiology and function has focused on fungal isolates morphologically identified as Rhizoscyphus ericae, in the Ascomycota order Helotiales, now known to be a Pezoloma species.

In addition to Rhizoscyphus ericae, it is currently recognized that culturable Ascomycota such as Meliniomyces (closely allied with Rhizoscyphus ericae), Cairneyella variabilis, Gamarada debralockiae and Oidiodendron maius form ericoid mycorrhizas. The application of DNA sequencing to fungal isolates and clones from environmental PCR has uncovered diverse fungal communities in ericoid roots, however, the ability of these fungi to form typical ericoid mycorrhizal coils has not been verified and some may be non-mycorrhizal endophytes, saprobes or parasites.

In addition to ascomycetes Sebacina species in the phylum Basidiomycota are also recognized as frequent, but unculturable, associates of ericoid roots, and can form ericoid mycorrhizas. Similarly, basidiomycetes from the order Hymenochaetales have also been implicated in ericoid mycorrhizal formation.

Geographic and host distribution分佈

The ericoid mycorrhizal symbiosis is widespread. 除了南極洲以外皆有分佈Ericaceae species occupy at least some habitats on all continents except Antarctica. 有少數杜鵑花科植物並沒有和杜鵑花菌根共生A few lineages within the Ericaceae do not form ericoid mycorrhizas, 而是形成其他種類的菌根and instead form other types of mycorrhizas,包含 including manzanita (Arctostaphylos), madrone (Arbutus), and the Monotropoidiae. The geographic distribution of many of the fungi is uncertain, primarily because the identification of the fungal partners has not always been easy, especially prior to the application of DNA-based identification methods. Fungi ascribed to Rhizoscyphus ericae have been identified from Northern and Southern Hemisphere habitats, but these are not likely all the same species. Some studies have also shown that fungal communities colonizing ericoid roots can lack specificity for different species of ericoid plant, suggesting that at least some of these fungi have a broad host range.

經濟重要性

杜鵑花菌根和多種作物及觀賞植物產生共生關係，包含藍莓、小紅莓和杜鵑花屬植物，能增加]植物吸收營養的能力。

小紅莓是一種和杜鵑花菌根共生的作物。

Northern highbush blueberries, Vaccinium corymbosum, an ericoid mycorrhizal crop

外部連結

• Mycorrhiza Literature Exchange