Influence of Plant Exudates on Root-Infecting Fungi

Schroth, and M N; Hildebrand, D. C.

doi:10.1146/annurev.py.02.090164.000533

Cited by 157 publications

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“…A number of common amino acids, including homoserine, were exuded by the growing seeding root in an early stage and were partly reabsorbed later. A number of uncommon amino acids, including several isoxazolin-5-one derivatives, uracil alanines, ia-yglutamyl-D-alanine, and a-aminoadipic acid were exuded at different rates.The range of compounds exuded by the roots of higher plants includes sugars, amino acids, enzymes, vitamins, nucleotides, growth hormones, terpenoids, flavanones, organic acids, and inorganic ions (22,24). By means of these exudates, the plants can affect the microflora in the rhizosphere by selective stimulation or inhibition of certain bacteria, fungi, or nematodes.…”

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“…The range of compounds exuded by the roots of higher plants includes sugars, amino acids, enzymes, vitamins, nucleotides, growth hormones, terpenoids, flavanones, organic acids, and inorganic ions (22,24). By means of these exudates, the plants can affect the microflora in the rhizosphere by selective stimulation or inhibition of certain bacteria, fungi, or nematodes.…”

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Isoxazolin-5-ones and Amino Acids in Root Exudates of Pea and Sweet Pea Seedlings

Kuo

Lambein²,

Ikegami³

et al. 1982

Plant Physiol.

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Seeds of Pisum sativum L. cv Finale and Lathyrs odoratus L. cv Spencer were germinated asepticafly in moistened sand in the dark. At several stages, the amino acid composition of the exudate and of the corresponding roots was analyzed. A number of common amino acids, including homoserine, were exuded by the growing seeding root in an early stage and were partly reabsorbed later. A number of uncommon amino acids, including several isoxazolin-5-one derivatives, uracil alanines, ia-yglutamyl-D-alanine, and a-aminoadipic acid were exuded at different rates.The range of compounds exuded by the roots of higher plants includes sugars, amino acids, enzymes, vitamins, nucleotides, growth hormones, terpenoids, flavanones, organic acids, and inorganic ions (22,24). By means of these exudates, the plants can affect the microflora in the rhizosphere by selective stimulation or inhibition of certain bacteria, fungi, or nematodes. There is also evidence that the root exudates of some plants inhibit the germination of some seeds or are toxic to roots of neighboring plants (22). It is generally believed that this root exudation is an uncontrolled process caused by damage to the cells at the root cap, at the sites where lateral roots emerge, and by infection of the root by microorganisms (23).Pea root exudates have been investigated in several laboratories (1,2,5,20,21,25). Some authors mentioned the presence of unknown amino acids (1,2,25). Rovira (20) showed the presence of UV-absorbing substances in 10-d-old and 21-d-old pea root exudates. Fries and Forsman (5) found some low mol wt UVabsorbing substances in the exudate from excised pea roots, besides adenine, guanine, uridine, and cytidine.A group of heterocyclic products, mostly amino acids, was isolated in our laboratory from pea seedlings and sweet pea seedlings: the uracil alanines willardiine and isowillardiine (15) and eight derivatives of the isoxazolin-5-one ring (13). (See Fig. 1 for the chemical structures.) Possibly, these products are the unknown compounds mentioned earlier by other authors (1, 2, 25).A preliminary study has shown the presence of some of these heterocycic products in root exudates of both pea and sweet pea seedlings (11). The differences in amino acid composition of the exudate and the corresponding root extract suggest that in some cases this exudation may be a specific phenomenon. This paper presents more detailed information on the exudation ofisoxazolin-5-one derivatives and other amino acids by intact roots ofetiolated pea and sweet pea seedlings under axenic conditions. MATERIALS AND METHODS Culture Conditions. Pea (Pisum sativum L. cv Finale) and sweet pea (Lathyrus odoratus L. cv Spencer) seeds were surface-sterilized with ethanol and were washed thoroughly with sterile distilled H20. After imbibing in sterile H20 for 16 h, the seeds were germinated in individual autoclaved glass tubes (20 x 2.8 cm), containing sterile quartz sand (5-cm height) moistened with distilled H20. The tubes were incubated at 25°C in the dark.Preparation...

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confidence: 99%

Isoxazolin-5-ones and Amino Acids in Root Exudates of Pea and Sweet Pea Seedlings

Kuo

Lambein²,

Ikegami³

et al. 1982

Plant Physiol.

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“…Most materials found in root cells are subject to such loss. Usually the simple sugars, organic acids, and alkaloids predominate, but minor cellular constituents such as inorganic ions and vitamins are also found (19).…”

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“…Considerable information relates the loss of organic substances from plant roots with increased population of soil microorganisms in the root zone (19). The relationship has been further extended to show correlations between levels of solute loss and disease incidence.…”

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Stimulation of Solute Loss from Radicles of Gossypium hirsutum L. by Chilling, Anaerobiosis, and Low pH

1970

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The loss of organic substances from cotton (Gossypium hirsutum L.) MATERIALS AND METHODS The seeds of Gossypium hirsutum L. used were from a selfpollinated M-8 genetic selection, a colchicine-doubled haploid from a Deltapine cultivar. Seed coats were removed to reduce germination variability due to differential permeability of seed coats to water.Seeds were germinated in gerniination paper rolls wet with distilled water. After sufficient germination time at 31 C to produce 2 cm long radicles (usually 24-26 hr), uniform seedlings were selected from the paper rolls, surface-sterilized with 0.1 % hypochlorite solution, rinsed in sterile water, and placed in stainless steel racks in Petri dishes with 1 cm of the seedling axis immersed in sterile solution. Each rack contained 20 seedlings; five racks were used for each treatment (five replications). The treatments were conducted in darkness. After completion of the assigned treatment (see below), the liquid in each dish was filtered, and the water was removed by freeze-drying. Preliminary assays and thin layer chromatographic studies showed that much of the dried residue consisted of carbohydrates and amino acids; these materials were, therefore, assayed and used as a measure of solute loss. The dried residue was redissolved in a small volume of 60 % methanol, and the solution was filtered and assayed for carbohydrates by the anthrone method (20). Ninhydrin-positive substances were determined by the method of Moore and Stein (14).The treatments applied to seedlings follow. RESULTS AND DISCUSSION Effect of Chilling, pH, and Anaerobic Conditions on Solute Loss. Low temperature induced large increases of solute loss from radicles (Fig. 1). The quantity of sugars and amino acids lost from roots held at 5 C increased with duration of chilling time. Thin layer chromatographs of the carbohydrates in the solution indicated that glucose, fructose, and sucrose were lost from roots at 5 C, whereas roots at 31 C lost only sucrose. Similar but more complex patterns were found on chromatograms 53 www.plantphysiol.org on April 27, 2019 -Published by Downloaded from

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Responses of Fungi to Nutrient-Limiting Conditions and to Inhibitory Substances in Natural Habitats

Lockwood

Filonow

1981

Advances in Microbial Ecology

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Influence of Plant Exudates on Root-Infecting Fungi

Cited by 157 publications

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Isoxazolin-5-ones and Amino Acids in Root Exudates of Pea and Sweet Pea Seedlings

Isoxazolin-5-ones and Amino Acids in Root Exudates of Pea and Sweet Pea Seedlings

Stimulation of Solute Loss from Radicles of Gossypium hirsutum L. by Chilling, Anaerobiosis, and Low pH

Responses of Fungi to Nutrient-Limiting Conditions and to Inhibitory Substances in Natural Habitats

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