The number of points with an arbuscle
or vesicle in the cells examined was converted to percent infection.
Endomycorrhizae usually form two distinct structures that develop in the plant root: an arbuscle
, which is a very fine, highly branched invagination into the cell, and a vesicle, which is a spherical structure forming between cells (Figure 9-21).
(1990) and roots that had vesicles, spores, hyphae and arbuscles
were considered colonized.
One-hundred colored root segments were separated for visualization of fungal structures (arbuscles
, vesicles and hyphae) using a stereomicroscope (40x).
RNA gel blot analysis showed the expression of LHA1 and LHA4 genes encoding H+-ATPase in cortical cells containing arbuscles
of Lycopersicon esculentum colonized by Glomus intraradices (Rosewarne et al., 2007).
may be a more informative measure of AMF functioning, and we were unable to definitively identify arbuscules in root samples.
The fungus penetrates the primary roots and spreads forming intra-cellular linear grouped hyphae in the rhizodermis and in the outermost cortical cell layers of the roots, developing hyphal enlargements at the distal hyphal tip, increasing the AMF surface; these structures look like incipient arbuscles (Fig.
Within the gametophyte chlorophillic cells, intracellular fungal hyphae were reported; the hyphae branched covering most of the prothallic cells and, in some cases, the hyphae managed to trespass the cell wall, establishing inter-cellular hyphae; however, no arbuscles were registered.
Mycorrhizae are formed with the roots of most vascular plants, taking the form of ectomycorrhizae (characterised by dense mycelial sheaths around the roots and intercellular hyphal invasion of the root cortex), which are mostly limited to temperate forest trees, or endomycorrhizae (characterised by external hyphal networks in the soil and extensive growth of arbuscles
(and commonly vesicles) within the root cortex cells of the host), which are formed by nearly all other plants.
The total percentage of root length colonized by AMF and the root length occupied by arbuscles
and vesicles are referred to as "fungal variables" in this study.
In an apparent answer to this question, Stubblefield and her colleagues report in the July 3 SCIENCE that they have found fossilized fungal organs, called arbuscles
, which Stubblefield says are the most definitive structural evidence for symbiosis.