Abstract
The impact of allelopathic, nonpathogenic bacteria on plant growth in natural and agricultural ecosystems is discussed. In some natural ecosystems, evidence supports the view that in the vicinity of some allelopathically active perennials (e.g., Adenostoma fasciculatum, California), in addition to allelochemicals leached from the shrub's canopy, accumulation of phytotoxic bacteria or other allelopathic microorganisms amplify retardation of annuals. In agricultural ecosystems allelopathic bacteria may evolve in areas where a single crop is grown successively, and the resulting yield decline cannot be restored by application of minerals. Transfer of soils from areas where crop suppression had been recorded into an unaffected area induced crop retardation without readily apparent symptoms of plant disease. Susceptibility of higher plants to deleterious rhizobacteria is often manifested in sandy or so-called skeletal soils. Evaluation of phytotoxic activity under controlled conditions, as well as ways to apply allelopathic bacteria in the field, is approached. The allelopathic effect may occur directly through the release of allelochemicals by a bacterium that affects susceptible plant(s) or indirectly through the suppression of an essential symbiont. The process is affected by nutritional and other environmental conditions, some may control bacterial density and the rate of production of allelochemicals. Allelopathic nonpathogenic bacteria include a wide range of genera and secrete a diverse group of plant growth-mediating allelochemicals. Although a limited number of plant growth-promoting bacterial allelochemicals have been identified, a considerable number of highly diversified growth-inhibiting allelochemicals have been isolated and characterized. Some species may produce more than one allelochemical; for example, three different phyotoxins, geldanamycin, nigericin, and hydanthocidin, were isolated from Streptomyces hygroscopicus. Efforts to introduce naturally produced allelochemicals as plant growth-regulating agents in agriculture have yielded two commercial herbicides, phosphinothricin, a product of Streptomyces viridochromogenes, and bialaphos from S. hygroscopicus. Many species of allelopathic bacteria that affect growth of higher plants are not plant specific, but some do exhibit specificity; for example, dicotyledonous plants were more susceptible to Pseudomonas putida than were monocotyledons. Differential susceptibility of higher plants to allelopathic bacteria was noted also in much lower taxonomical categories, at the subspecies level, in different cultivars of wheat, or of lettuce. Therefore, when test plants are employed to evaluate bacterial allelopathy, final evaluation must include those species that are assumed to be suppressed in nature. The release of allelochemicals from plant residues in plots of ‘continuous crop cultivation’ or from allelopathic living plants may induce the development of specific allelopathic bacteria. Both the rate by which a bacterium gains from its allelopathic activity through utilizing plant excretions, and the reasons for the developing of allelopathic bacteria in such habitats, are important goals for further research.
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Claims 12
Claim · model-written summary
Phytotoxic microorganisms may amplify retardation of annuals near Adenostoma fasciculatum.
Verbatim
e0“in the vicinity of some allelopathically active perennials (e.g., Adenostoma fasciculatum, California), in addition to allelochemicals leached from the shrub's canopy, accumulation of phytotoxic bacteria or other allelopathic microorganisms amplify retardation of annuals”
Claim · model-written summary
Allelopathic bacteria may develop in successive single-crop agriculture with yield decline not restored by mineral application.
Verbatim
e0“allelopathic bacteria may evolve in areas where a single crop is grown successively, and the resulting yield decline cannot be restored by application of minerals”
Claim · model-written summary
Transfer of suppression-associated soil induced crop retardation in an unaffected area.
Verbatim
e0“Transfer of soils from areas where crop suppression had been recorded into an unaffected area induced crop retardation without readily apparent symptoms of plant disease”
Claim · model-written summary
Higher-plant susceptibility to deleterious rhizobacteria often appeared in sandy or skeletal soils.
- Taxon
- higher plantsEmbryophytae0
- Interactor
- deleterious rhizobacteriae0other
- Outcome
- Susceptibilitye0
- Setting
- sandy or so-called skeletal soilse0
Verbatim
e0“Susceptibility of higher plants to deleterious rhizobacteria is often manifested in sandy or so-called skeletal soils”
Claim · model-written summary
Bacterial allelochemical release may directly affect susceptible plants.
Verbatim
e0“The allelopathic effect may occur directly through the release of allelochemicals by a bacterium that affects susceptible plant(s)”
Claim · model-written summary
Suppression of an essential symbiont may indirectly cause bacterial allelopathy.
- Taxon
- higher plantsEmbryophytat0
- Interactor
- symbionte0symbiont
- Outcome
- suppression of an essential symbionte0
- Qualifier
- indirectlye0
Verbatim
e0“or indirectly through the suppression of an essential symbiont”
t0“Higher Plants”
Claim · model-written summary
Nutritional and environmental conditions may affect bacterial density and allelochemical production.
- Taxon
- Higher PlantsEmbryophytat0
- Outcome
- bacterial density and the rate of production of allelochemicalse0
- Qualifier
- nutritional and other environmental conditionse0
Verbatim
e0“The process is affected by nutritional and other environmental conditions, some may control bacterial density and the rate of production of allelochemicals”
t0“Higher Plants”
Claim · model-written summary
Some allelopathic bacteria affect growth of higher plants without plant specificity.
- Taxon
- higher plantsEmbryophytae0
- Interactor
- allelopathic bacteriae0other
- Outcome
- growth of higher plantse0
Verbatim
e0“Many species of allelopathic bacteria that affect growth of higher plants are not plant specific”
Claim · model-written summary
Dicotyledonous plants were more susceptible to Pseudomonas putida than monocotyledons.
- Taxon
- dicotyledonous plantse0
- Interactor
- Pseudomonas putida
Pseudomonas putidae0other - Outcome
- susceptiblee0
- Direction
- more susceptiblee0
- Comparator
- monocotyledonse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“dicotyledonous plants were more susceptible to Pseudomonas putida than were monocotyledons”
Claim · model-written summary
Wheat cultivars differed in susceptibility to allelopathic bacteria.
- Taxon
- wheat
Triticum aestivume0 - Interactor
- allelopathic bacteriae0other
- Outcome
- Differential susceptibilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Differential susceptibility of higher plants to allelopathic bacteria was noted also in much lower taxonomical categories, at the subspecies level, in different cultivars of wheat”
Claim · model-written summary
Lettuce cultivars differed in susceptibility to allelopathic bacteria.
- Taxon
- lettuce
Lactuca sativae0 - Interactor
- allelopathic bacteriae0other
- Outcome
- Differential susceptibilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Differential susceptibility of higher plants to allelopathic bacteria was noted also in much lower taxonomical categories, at the subspecies level, in different cultivars of wheat, or of lettuce”
Claim · model-written summary
Plant species expected to be suppressed in nature should be included in final bacterial allelopathy evaluation.
- Taxon
- Higher PlantsEmbryophytat0
- Outcome
- final evaluation must include those species that are assumed to be suppressed in naturee0
Verbatim
e0“final evaluation must include those species that are assumed to be suppressed in nature”
t0“Higher Plants”