Pathological Changes in Ultrastructure: Effects of Victorin on Oat Roots

Abstract

Cells in the interior of susceptible oat roots treated with the disease‐inducing agent victorin exhibit many of the ultrastructural features which characterize the epidermal or outermost root cap cells of untreated roots. An increase in electron density of cell walls fixed in permanganate is the first effect of victorin seen in the root interior. Other early victorin‐induced changes are formation of enlarged, densely stained vesicles by the Golgi apparatus and organization of the endoplasmic reticulum into roughly parallel profiles. All of these features are characteristic of untreated epidermal cells. Victorin also induces the formation of large numbers of lomasome‐like wall lesions and causes a marked increase in the number of nearly spherical, membrane‐bounded structures tentatively identified as spherosomes. Similar lomasome‐ and spherosome‐like structures are much more abundant in the outermost cells of the root cap than in other regions of untreated roots. This suggests that these structures may be characteristic of cells destined to undergo disintegration. Victorin‐induced lesions appear to arise within the cell wall as the result of an activation of wall‐degrading enzymes. An early change which makes the unit structure of the plasma membrane visible over extended areas may account for victorin‐induced changes in permeability. Disrupted plasma membranes and swollen mitochondria are found only in cells heavily damaged by victorin. Many of the effects of victorin resemble those of calcium deficiency and calcium is known to suppress victorin‐induced disease symptoms. This suggests that calcium nutrition may play a role in the pathological changes induced by victorin.

Localization of Crystals in Diseased Oats Treated with Uranyl Acetate

“…Effects on chlorenchyma cells outside the vascular bundle were slight, although occasional plasmolysis, chloroplast damage, and cell wall lesions were observed. These effects were similar to those previously described (5)(6)(7).…”

Effect of a host-specific toxin (AM-toxin I) produced by Alternaria mali, an apple pathogen, on the ultrastructure of plasma membrane of cells in apple and Japanese pear leaves

“…Six hours after treatment, susceptible cells showed many invaginations of the plasma membrane (Figs. [6][7][8]. However, the changes in the ~l a s m a membrane were not evident at 30 min after treatment.…”

“…Although permeability changes were not always recognized in many ultrastructural studies, similar structural changes at the interfaces of plasma membrane and cell wall were observed. Similar structural changes were variously termed lomasome-like structures or lomasomes (4), paramural bodies (9), boundary formation (24), wall appositions (8), callose deposition (I), cell wall lesion (6), cell border lesion (lo), wall blisterlike structures (12), and depositions of darkly stained materials (7). The writers consider plasma membrane modifications in the infection process to be common changes in plant cells for which a change in permeability has been induced.…”

Microscopy of soybean seeds: cellular and subcellular structure during germination, development and processing with emphasis on lipid bodies

“…Electron microscopy There is disagreement on which of the cytoplasmic bodies visible in the electron microscope represent spherosomes Mix, 1962, 1963;Frey-Wyssling et al, 1963;Hanchey et al, 1968;Hohl, 1960a;Peveling, 1962). According to Frey-Wyssling et al (1963), spherosomes were identified as irregular sacs containing a characteristic granulation, which was referred to as the stroma of the spherosome.…”