Further Studies of Osmotic and Permeability Relations in Parasitism

mentioning

confidence: 99%

Detrimental Effect of Rust Infection on the Water Relations of Bean

Duniway

Durbin

1971

“…Because S. sclerotiorum is reported to induce drastic permeability increases well in advance of lesions, this system was chosen for further study (27,28). As my results show, original interpretations (27,28) Sunflower (Helianthus annuus) seedlings were grown in the greenhouse (22-28 C). When seedlings were 15 to 20 days old (three sets of true leaves; hypocotyl diameter at soil level, 0.5-0.7 cm), they were inoculated with mycelial blocks (3 X 3 mm) cut from margins of fungal colonies grown on potato dextrose agar in Petri plates.…”

mentioning

confidence: 99%

Changes in Cell Membrane Permeability in Sunflower Hypocotyls Infected with Sclerotinia sclerotiorum

Hancock

1972

Influx and efflux of water and urea and electrolyte leakage are less for sunflower (Helianthus annuus) hypocotyl sections above lesions caused by Sclerotinia sclerotiorum than for those from healthy plants. Urea uptake by sections above lesions is reduced (celery, squash, and tomato) or unchanged (bean) in other hosts after Sclerotinia infection. Efflux of urea from sunflower hypocotyls is biphasic, suggesting diffusion in series from two cellular compartments (cytoplasm and vacuole). Efflux during the fast phase was 7 to 20 times greater than that during the slow phase. No difference was noted in urea efflux from healthy and diseased tissues during the slow phase. However, efflux during the fast phase from diseased tissues was slower than from healthy tissues, suggesting that the increased resistance to diffusion of urea in host cells above lesions resides in the plasmalemma. Water movement across cell membranes of healthy and diseased sunflower hypocotyls was reduced when tissues were treated with p-hydroxymercuriben. Increases in host cell permeability often occur at sites of infection by facultative parasites (11,14,31). Increases in permeability may be caused by pathogen elaborated products or host cell responses to infection. When membrane permeability is drastically altered, cell death follows shortly.The effects of disease on cell permeability in tissues further removed from lesions is still poorly documented. Some workers have reported increases in cell permeability large distances from lesions (14, 27), while others report no differences in permeability between host cells bordering lesions and those in healthy plants (7,11). In one disease, decreases in the permeability of host cells bordering lesions were observed (28).Thatcher's (27) studies on permeability changes in diseases caused by Sclerotinia sclerotiorum and Botrytis cinerea have emphasized increases in host cell permeability some distance from sites of pathogen activity. He reported that permeability was greatly increased in celery petiole cells "inches away from any sign of necrosis" in soft rots caused by these fungi. The "action in advance" phenomenon observed in these diseases has been the subject of much attention since it could relate to processes unique to pathogenesis and account for certain ' The author is indebted to Professor R. K. S. Wood and the De-partment of Botany, Imperial College, London, for providing facilities for part of this investigation. This work was supported partially by funds received from Hatch Project No. 2376. changes in host physiology. The action of host specific toxins (21, 31) and extracellular enzymes (9, 14, 17, 24) on plant cells lends credibility to the notion that permeability increases well in advance of infection sites.More studies on cell permeability in infected plants are needed to clarify the nature and significance of permeability changes in host cells. Because S. sclerotiorum is reported to induce drastic permeability increases well in advance of lesions, this system was chosen for ...

“…Increases in host membrane permeability are detectable prior to symptom *expression during infection by Rhizoctonia solani Kuhn (13) and well in advance of lesions in other diseases (21,22,24 …”

mentioning

confidence: 99%

“…But Clues to mechanisms of pathogenicity of plant pathogenic fungi and bacteria may be obtained from early physiological and biochemical symptoms. Though an indirect approach to studies on physiology of pathogen!icitv must be applied cautiously, studies oIn early stages of infection can provide new information onl processes peculiar to pathogenesis.Changes in cell membrane permeability are an early symptom in many plant diseases (9,13,22,24,25). Increases in host membrane permeability are detectable prior to symptom *expression during infection by Rhizoctonia solani Kuhn (13) and well in advance of lesions in other diseases (21,22,24 …”

mentioning

confidence: 99%

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Effect of Infection by Hypomyces solani f. sp. Cucurbitac on Apparent Free Space, Cell Membrane Permeability, and Respiration of Squash Hypocotyls

Hancock

1968

Abstract. Initial symptoms and increases in respiration, apparent free space, and rate of leakage of amino acids occurred concomitantly in squash (Cucurbita maxima Dcne) hypocotyls infeoted by Hypomyces solani f. sp. cucurbitae Snyd. and Hans. Young, rapidly expanding lesions had greater respiratory rates and apparent free space than comparable tissues from healthy plants.Hypocotyl tissues a,bove (145 mm) lesions possessed greater endogenous respira,torv rates (2-3 times) and lower respiratory quotients than similar tissues from 'healthy plants. But Clues to mechanisms of pathogenicity of plant pathogenic fungi and bacteria may be obtained from early physiological and biochemical symptoms. Though an indirect approach to studies on physiology of pathogen!icitv must be applied cautiously, studies oIn early stages of infection can provide new information onl processes peculiar to pathogenesis.Changes in cell membrane permeability are an early symptom in many plant diseases (9,13,22,24,25). Increases in host membrane permeability are detectable prior to symptom *expression during infection by Rhizoctonia solani Kuhn (13) and well in advance of lesions in other diseases (21,22,24