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1

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Nitrogen availability and susceptibility of tomato leaves to Botrytis cinerea (1999)

Hoffland, Ellis ; van Beusichem, Marinus L. ; Jeger, Michael J.

Springer

Plant and soil 210 (1999), S. 263-272

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ISSN: 1573-5036

Keywords: Botrytis cinerea ; Lycopersicon esculentum ; nitrogen availability ; pathogen resistance ; relative growth rate ; α-tomatine

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract The aim of this study was to investigate the effect of nitrogen availability on susceptibility of tomato leaves to the fungal pathogen Botrytis cinerea. Plants with varying nitrogen availability were grown by adding N daily in exponentially increasing amounts to a nutrient solution at different rates. Leaves of plants grown at low nitrogen availability had a high leaf C/N ratio (21 g g-1) and were about 2.5 times more susceptible to primary lesion formation by B. cinerea compared to plant grown at high nitrogen availability, which had a low leaf C/N ratio (11 g g-1). Leaf C/N ratio accounted for 95% of variation in susceptibility. This relationship between C/N ratio and susceptibility persisted when plants were grown with exponential P addition and optimal N supply, and was thus independent of plant growth rate or related factors. We could not explain the effect of nitrogen availability by variation in the most obvious N-based resistance compound α-tomatine because more susceptible leaves with a high C/N ratio contained more α-tomatine. These leaves also contained more soluble carbohydrates. The level of soluble carbohydrates correlated positively with susceptibility, independent of the growth method. We therefore suggest that the effect of N availability on susceptibility must be explained by variation in levels of soluble carbohydrates and speculate about the role of these carbohydrates in the infection process.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004661913224

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2

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Effect of nitrogen supply rate on disease resistance in tomato depends on the pathogen (2000)

Hoffland, Ellis ; Jeger, Michael J. ; van Beusichem, Marinus L.

Springer

Plant and soil 218 (2000), S. 239-247

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ISSN: 1573-5036

Keywords: disease resistance ; Fusarium oxysporum ; Lycopersicum esculentum ; nitrogen supply ; Oidium lycopersicum ; Pseudomonas syringae

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract The aim of this study was to investigate the effect of tissue nitrogen concentration, as a consequence of nitrogen supply rate, on the susceptibility of tomato plants to three pathogens. We varied tissue N concentration by supplying N at different rates by adding nitrate in different, exponentially increasing amounts to the nutrient solution on which the tomato plants were grown. Separate experiments were carried out to test susceptibility of tomato plants to the bacterial speck-causing Pseudomonas syringae pv tomato, to the wilt agent Fusarium oxysporum f.sp. lycopersici and to tomato powdery mildew caused by Oidium lycopersicum. The effect of tissue N concentration appeared to be highly pathogen-dependent: there was no effect on susceptibility to F. oxysporum, but susceptibility to P. syringae and O. lycopersicum increased significantly with increasing N concentration. We have previously demonstrated the opposite for susceptibility to Botrytis cinerea: decreasing susceptibility with increasing N concentration. The apparent contradictory effects are discussed in relation to the effect of N supply on both the nutritional value of the plant tissue to the pathogen and on the concentration of resistance-related compounds. We conclude that the effect of changing both characteristics on disease susceptibility is highly pathogen-specific and is probably dependent on differences in resource requirements of the pathogen or the sensitivity of the pathogen to plant resistance reactions or on both these factors.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1014960507981

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3

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Quantitative evaluation of the role of organic acid exudation in the mobilization of rock phosphate by rape (1992)

Hoffland, Ellis

Springer

Plant and soil 140 (1992), S. 279-289

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ISSN: 1573-5036

Keywords: Brassica napus L. ; citric acid ; malic acid ; pH gradient ; phosphate uptake ; rhizosphere ; rock phosphate ; root exudation ; root hairs ; simulation

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Phosphorus-deficient rape plants appear to acidify part of their rhizosphere by exuding malic and citric acid. A simulation model was used to evaluate the effect of measured exudation rates on phosphate uptake from Mali rock phosphate. The model used was one on nutrient uptake, extended to include both the effect of ion uptake and exudation on rhizosphere pH and the effect of rhizosphere pH on the solubilization of rock phosphate. Only the youngest zones of the root system were assumed to exude organic acids. The transport of protons released by organic acids was described by mass flow and diffusion. An experimentally determined relation was used describing pH and phosphate concentration in the soil solution as a function of total soil acid concentration. Model parameters were determined in experiments on organic acid exudation and on the uptake of phosphate by rape from a mixture of quartz sand and rock phosphate. Results based on simulation calculations indicated that the exudation rates measured in rape plants deficient in phosphorus can provide the roots with more phosphate than is actually taken up. Presence of root hairs enhanced the effect of organic acid exudation on calculated phosphate uptake. However, increase of root hair length without exudation as an alternative strategy to increase phosphate uptake from rock phosphate appeared to be less effective than exudation of organic acids. It was concluded that organic acid exudation is a highly effective strategy to increase phosphate uptake from rock phosphate, and that it unlikely that other rhizosphere processes play an important role in rock phosphate mobilization by rape.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00010605

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4

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Nitrogen Availability and Defense of Tomato Against Two-spotted Spider Mite (2000)

Hoffland, Ellis ; Dicke, Marcel ; Van Tintelen, Willeke ; [et al.]

Springer

Journal of chemical ecology 26 (2000), S. 2697-2711

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ISSN: 1573-1561

Keywords: Lycopersicon esculentum ; tomato ; Tetranychus urticae ; spider mite ; nitrogen availability ; defense ; trichome ; odor ; volatile ; phenolics ; resource availability

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract The aim of this work was to study how nitrogen availability affects within-plant allocation to growth and secondary metabolites and how this allocation affects host selection by herbivores. Tomato plants (Lycopersicon esculentum) were grown at six levels of nitrogen availability. When nitrogen availability increased, plant relative growth rate increased, but tissue carbon/nitrogen ratio in the second oldest true leaf and allocation to large glandular trichomes (type VI) as well as to the defense compounds rutin and chlorogenic acid decreased. Leaf protein concentration increased. Two-spotted spider mite (Tetranychus urticae) females responded significantly to these changes: in dual choice tests they preferred leaf disks from plants grown at high nitrogen availability, with a low C/N ratio. This preference persisted in an olfactometer in which the mites were offered only the odors released by leaves with damaged trichomes. We conclude that in a tomato leaf increased nitrogen availability leads to decreased allocation to defenses, and that repellent volatiles released by trichomes play a key role in affecting leaf selection by two-spotted spider mite females.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1026477423988

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5

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Solubilization of rock phosphate by rape (1989)

Hoffland, Ellis ; Findenegg, Günter R. ; Nelemans, Jacob A.

Springer

Plant and soil 113 (1989), S. 155-160

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ISSN: 1573-5036

Keywords: Brassica napus ; Ca uptake ; cation-anion balance ; rock phosphate ; split pot experiments

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Rape and sunflower were compared with respect to their rock phosphate mobilizing capacities, cationanion balance and uptake of Ca and NO3 at P-starvation. Rape was able to mobilize P from rock phosphate, whereas sunflower was not. When grown on a complete nutrient solution with NO3 as the only nitrogen source, both species took up more nutrient anions than cations. Withholding phosphate from the nutrient solution did not change the uptake pattern of rape, but sunflower took up more nutrient cations than anions at P-starvation, due to a strong decline in NO3 uptake. With both species, Ca uptake was not affected by phosphate in the nutrient solution. In split pot experiments, with rock phosphate supplied spatially separated from other nutrients, rape was still able to mobilize rock phosphate. A high Ca concentration had no effect on this capacity. The results indicated that in our experiments rock phosphate mobilization by rape was not associated with an excess of cation over anion uptake and neither with a high Ca uptake rate.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02280175

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6

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Solubilization of rock phosphate by rape (1989)

Hoffland, Ellis ; Findenegg, Günter R. ; Nelemans, Jacob A.

Springer

Plant and soil 113 (1989), S. 161-165

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ISSN: 1573-5036

Keywords: agar plate technique ; Brassica napus ; citric acid ; malic acid ; phosphate nutrition ; rhizosphere acidification

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Local rhizosphere acidification by rape as a reaction to P-starvation was visualized by means of an agar plate technique. By means of a modification of this technique local differences in cation-anion uptake and organic acid exudation along intact roots of rape were observed for plants grown on nutrient solution with or without added P. No differences in uptake rates of K-, NO3- and Ca-ions could be detected between P-starved and P-supplied plants. However, exudation of malic and citric acid was distinctly higher in acidified root zones of P-starved plants, coinciding with higher levels of malate in the corresponding root tissue. Organic acid exudation is indicates as the cause of local rhizosphere acidification by rape as a reaction to P-starvation and as a possible mechanism of its phosphate-solubilizing capacity.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02280176

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