The roots and mycorrhizas of herbaceous woodland plants

Abstract

SUMMARYThe morphology of vesicular-arbuscular (VA) mycorrhizas in the roots of five species of herbaceous woodland plants, in which root growth and mycorrhiza formation were quantified in the first part of this study was examined, i he root anatomy of these species was also examined in detail, using various staining procedures to observe cell wall structure, especially in the region where mycorrhizal colonization was initiated. The morphology of mycorrhizal colonies within the roots of these species was observed at different stages of development using light microscopy. It was found that modifications of endodermal and exodermal cell-walls could determine the way in which fungi entered the roots. It was also found that properties of the cortex considerably infiuenced the localization of hyphae and arbuscules within roots. Features of VA mycorrhizas that were probably associated with particular endophytes were also noted. It is considered likely that some aspects of root structure have evolved means of regulating the efficiency of mycorrhizal associations.

Structural diversity in (vesicular)–arbuscular mycorrhizal symbioses

“…However, despite the lack of quantitative measurements of surface areas, there is no doubt whatsoever that the intracellular hyphal coils can be extremely extensive compared with arbuscules, as shown by illustrations in many publications (e.g. Brundrett & Kendrick, 19906;Whitbread et al, 1996;Widden, 1996), and as we have found with our own observations . If there is spatial separation of transfer, the coils could be the site of transfer of organic C, with transfer of P across the localized arbuscular interface.…”

“…The elegant iUustrations in the recent papers (light and scanning electron micrographs) show the presence of arbuscules associated with intracellular hyphal coils. Brundrett & Kendrick (19906) suggested that it is not yet clear which class is the most common. This comment has led to our surveying the literature in an attempt to assess the extent of P«r/5-types in relation to Arumtypes.…”

Branched absorbing structures (BAS): a feature of the extraradical mycelium of symbiotic arbuscular mycorrhizal fungi

“…Arbuscules develop along intraradical, intercellular ' runner ' hyphae or intracellular coils (3-4 µm, Bonfante-Fasolo (1984) Brundrett & Kendrick (1990) ;Widden, (1996)), their number being proportional to the amount of intercellular hyphae growing along the internal cortex of the host root (Arum-type arbuscular mycorrhiza, Bennett, (1986) ; Toth et al (1990)). It is interesting to note that the formation of both structures is repeated along fungal hyphae, growing either intraradical or extraradically.…”

Diversity of Arbuscular Mycorrhizae Fungi from Orchard Ecosystem

“…Firstly, disparity in sporulation ability of different AM fungi species can result in unevenness of spore density [39]. Secondly, the occurrence of interspecific competition among AM fungi is possible in the soil and within roots [40]. Also seasonality, spatial and temporal variation, complex below ground structure, host-preference and disturbance are generally thought to coincide with the variation of AM fungi distribution and community structure [41][42][43][44][45].…”