Photosynthesis in green-islands on powdery mildewinfected barley leaves

Coghlan, S.; Walters, Dale R.

doi:10.1016/0885-5765(92)90069-8

Cited by 21 publications

(13 citation statements)

References 16 publications

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“…The induction of senescence may be a response to pathogen attack; the chlorosis of leaves that often occurs 607 around the sites of pathogen invasion would support this hypothesis. Some invading pathogens, such as rust and mildew, synthesise cytokinins, resulting in the so called 'green islands' surrounding sites of infection [7,35]. Since cytokinins are known to delay leaf senescence in many species [42], this action by the pathogen may be a precaution to inhibit the plant's response to invasion.…”

Section: Discussionmentioning

confidence: 99%

Leaf senescence in Brassica napus: expression of genes encoding pathogenesis-related proteins

1996

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Genes that are expressed during leaf senescence in Brassica napus were identified by the isolation of representative cDNA clones. DNA sequence and deduced protein sequence from two senescence-related cDNAs, LSC94 and LSC222, representing genes that are expressed early in leaf senescence before any yellowing of the leaves is visible, showed similarities to genes for pathogenesis-related (PR) proteins: a PR-1a-like protein and a class IV chitinase, respectively. The LSC94 and LSC222 genes showed differential regulation with respect to each other; an increase in expression was detected at different times during development of healthy leaves. Expression of both genes was induced by salicylic acid treatment. These findings suggest that some PR genes, as well as being induced by pathogen infection, may have alternative functions during plant development, for example in the process of leaf senescence.

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Section: Discussionmentioning

confidence: 99%

Leaf senescence in Brassica napus: expression of genes encoding pathogenesis-related proteins

1996

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“…In many fungal infections (Klecan and Buchanan, 1988;McDonald and Strobel, 1970;Mirocha and Zaki, 1966), starch also accumulates inside infected lesions, particularly those described as dark green islands (Coghlan and Waiters, 1992;Scholes and Farrar, 1986;Wang, 1961). It is believed that this is because fungal growth causes the lesions to become sinks for photosynthate produced in surrounding uninfected regions of the leaf.…”

Section: T I M E P O S T -I N F E C T I O N (D)mentioning

confidence: 99%

Complex, localized changes in CO₂ assimilation and starch content associated with the susceptible interaction between cucumber mosaic virus and a cucurbit host

et al. 1994

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SummaryInfection of the cotyledons of Cucurbita pepo L. with cucumber mosaic virus (CMV) results in the formation of chlorotic, starch-containing lesions. To characterize the physiological changes occurring within lesions, the distribution of the virus was examined by immunolocalization and correlated with starch accumulation, 14CO2 assimilation and chlorophyll a fluorescence quenching. These techniques resolved the lesion into a complex and reproducible arrangement of cell types of diveree physiology. The region of infected cells extended beyond specific circular zones of cells which variously showed enhanced rates of CO2 assimilation, enhanced chlorophyll a fluorescence quenching, starch accumulation, starch degradation and chlorosis. This indicates a series of physiological changes occurring over several days following viral replication within a cell. Starch accumulation in the lesion was shown to result from photosynthetic activity of cells within the lesion and not from the import of photosynthate from surrounding uninfected areas of the cotyledon.

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“…83%, of incident light (as suggested in Harley et al, 1992). However, many foliar diseases reduce light absorption by either a reduction in chlorophyll content or fungal hyphae on needle surfaces blocking light penetration (Wood et al, 1988; Coghlan and Walters, 1992; Scholes and Rolfe, 1996). While light absorption was not directly measured in this study, it appears that light absorption was not influenced by P. gaeumannii infection, because similar chlorophyll contents and a linear relationship between calculated ETR and A net were observed for both control and infected foliage.…”

Section: Discussionmentioning

confidence: 99%

Energy Dissipation and Photoinhibition in Douglas‐Fir Needles with a Fungal‐Mediated Reduction in Photosynthetic Rates

Manter¹

2002

Journal of Phytopathology

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The dissipation of absorbed light and potential for photooxidative damage was explored in Douglas‐fir (Pseudotsuga menziesii ) seedlings with and without Phaeocryptopus gaeumannii infection. The presence of P. gaeumannii significantly reduced net CO2 assimilation rates from ca. 6 μmol/m2/s to 1.5 μmol/m2/s, without any significant impact on chloroplast pigments. The partitioning of absorbed light‐energy to photochemistry or thermal dissipation was determined from chlorophyll fluorescence measurements. Maximum thermal dissipation for both control and infected needles was ca. 80%, consistent with the similar xanthophyll pool sizes in the two treatments. At high photosynthetic photon flux density (PPFD), when thermal dissipation was maximized, the lower photochemical utilization in infected needles resulted in greater amounts of excess absorbed light (ca. 20 and 10% for the infected and control needles, respectively). A second experiment, monitoring changes in photosystem II (PSII) efficiency (Fv/Fm) in response to a 1 h high light treatment (PPFD=2000 μmol/m2/s) also suggests that infected needles absorb greater amounts of excess light. In this experiment, declines in Fv/Fm were 1.5 times greater in infected needles, despite the similar xanthophyll pool sizes. Furthermore, increases in minimum fluorescence (178 and 122% of initial values for the infected and control needles, respectively) suggest that the reduction in PSII efficiency is largely attributable to photooxidative damage. Finally, reductions in PSII efficiency under high light conditions provide a plausible explanation for the greater pathogenicity (e.g. premature needle abscission) of P. gaeumannii in sun‐exposed foliage.

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Photosynthesis in green-islands on powdery mildewinfected barley leaves

Cited by 21 publications

References 16 publications

Leaf senescence in Brassica napus: expression of genes encoding pathogenesis-related proteins

Leaf senescence in Brassica napus: expression of genes encoding pathogenesis-related proteins

Complex, localized changes in CO₂ assimilation and starch content associated with the susceptible interaction between cucumber mosaic virus and a cucurbit host

Energy Dissipation and Photoinhibition in Douglas‐Fir Needles with a Fungal‐Mediated Reduction in Photosynthetic Rates

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Photosynthesis in green-islands on powdery mildewinfected barley leaves

Cited by 21 publications

References 16 publications

Leaf senescence in Brassica napus: expression of genes encoding pathogenesis-related proteins

Leaf senescence in Brassica napus: expression of genes encoding pathogenesis-related proteins

Complex, localized changes in CO2 assimilation and starch content associated with the susceptible interaction between cucumber mosaic virus and a cucurbit host

Energy Dissipation and Photoinhibition in Douglas‐Fir Needles with a Fungal‐Mediated Reduction in Photosynthetic Rates

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Complex, localized changes in CO₂ assimilation and starch content associated with the susceptible interaction between cucumber mosaic virus and a cucurbit host