Features of Mycorrhizal Infection in Some Malayan Orchids

Abstract

Summary In the roots of most species of terrestrial and epiphytic Malayan orchids examined, mycorrhizal infection was spasmodic and confined to a small proportion of the root cortex cells. Only a few terrestrial species exhibited the pattern of dense infection seen in north temperate orchids. Chlorophyllous tissue in the roots of some terrestrial and epiphytic species was invaded and cytological changes, including fragmentation and disappearance of the chloroplasts, occurred in some instances. Measurements of host cell nuclei indicated that nuclear hypertrophy occurred not only in infected cells but also in many non‐infected cells localized around pockets of infection.

Occurrence and intensity of mycorrhizal infections in cultivated orchids in some New Zealand nurseries

“…Similarly, aerial roots of 12-year-old Vanda cristata (Table 1) had no mycorrhizal infection whereas the soil roots of the same plant showed 23% infection. This supports an earlier observation made by Hadley and Williamson (1972) in some Malaysian orchids. Warcup (1981) pointed out that non-mycorrhizal aerial roots were an effect of lack of root contact with the substrate (potting mix harbouring mycorrhizal fungi) rather than one of the chlorophyll, because green roots attached to a substrate may be well infected.…”

“…There were very low mycorrhizal infection levels (2-4%) in Lycaste (Jason x Koelene) and Pleione hookerianum (Table 1) probably because of the high frequency of root shedding in these 2 plants. Very low mycorrhizal infections (often with 0% infections in different segments of the root) have been reported in some tropical orchids (Hadley & Williamson 1972). Intensity of mycorrhizal infection in different hybrids of the same genus seem to "Vary, as could be seen in different Cymbidium hybrids of similar age raised in the same glasshouse (Table 1).…”

“…Four root sections were randomly selected for each plant sample, cold-stained with trypan blue, and examined under the microscope at x 200 magnification. Percentage infection intensity in each root section was assessed by eye as the number of infected cortical cells out of the total number of cells available for infection (Hadley & Williamson 1972). The percent infection data presented in Table 1 are mean values from the sections examined for each orchid sample ..…”

Anatomia de raízes de espécies de Orchidaceae do Parque Estadual da Serra do Brigadeiro, Minas Gerais

“…Foram visualizadas micorrizas nas espécies estudadas, assemelhando-se aos pélotons descritos por Hadley & Williamson (1972) e Benzing & Friedman (1981). A ocorrência de micorrizas em Orchidaceae é indiscutivelmente aceita (Hadley & Williamson 1972).…”

“…A ocorrência de micorrizas em Orchidaceae é indiscutivelmente aceita (Hadley & Williamson 1972). As orquídeas possuem dependência de associação de fungos micorrízicos para germinação das sementes e, quando adultas, pode-se verificar infecções no sistema radicular de muitos indivíduos (Benzing & Friedman 1981).…”