Abstract
The survival of Azospirillum brasilense Cd and Sp-245 in the rhizosphere of wheat and tomato plants and in 23 types of plant-free sterilized soils obtained from a wide range of environments in Israel and Mexico was evaluated. Large numbers of A. brasilense cells were detected in all the rhizospheres tested, regardless of soil type, bacterial strain, the origin of the soil, or the amount of rainfall each soil type received prior to sampling. Survival of A. brasilense in soils without plants differed from that in the rhizosphere and was mainly related to the geographical origin of the soil. In Israeli soils from arid, semiarid, or mountain regions, viability of A. brasilense rapidly declined or populations completely disappeared below detectable levels within 35 days after inoculation. In contrast, populations in the arid soils of Baja California Sur, Mexico, remained stable or even increased during the 45-day period after inoculation. In soils from Central Mexico, viability slowly decreased with time. In all soils, percentages of clay, nitrogen, organic matter, and water-holding capacity were positively correlated with bacterial viability. High percentages of CaCO(inf3) and fine or rough sand had a highly negative effect on viability. The percentage of silt, pH, the percentage of phosphorus or potassium, electrical conductivity, and C/N ratio had no apparent effect on bacterial viability in the soil. Fifteen days after removal of inoculated plants, the remaining bacterial population in the three soil types tested began to decline sharply, reaching undetectable levels 90 days after inoculation. After plant removal, percolating the soils with water almost eliminated the A. brasilense population. Viability of A. brasilense in two artificial soils containing the same major soil components as the natural soils from Israel did was almost identical to that in the natural soils. We conclude that A. brasilense is a rhizosphere colonizer which survives poorly in most soils for prolonged periods of time; that outside the rhizosphere, seven abiotic parameters control the survival of this bacterium in the soil; and that disturbance of the soil (percolation with water or plant removal) directly and rapidly affects the population levels.
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Claims 11
Claim · model-written summary
Large Azospirillum populations occurred in all tested wheat and tomato rhizospheres regardless of soil or strain.
- Taxon
- wheat and tomato plants
Solanum lycopersicum
Triticum aestivume1 - Interactor
- A. brasilense
Azospirillum brasilensee0symbiont - Outcome
- Large numbers of A. brasilense cellse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Large numbers of A. brasilense cells were detected in all the rhizospheres tested, regardless of soil type, bacterial strain, the origin of the soil, or the amount of rainfall each soil type received prior to sampling.”
e1“rhizosphere of wheat and tomato plants”
Claim · model-written summary
Azospirillum survival in plant-free soil differed from survival in the rhizosphere and was mainly associated with soil origin.
- Taxon
- wheat and tomato plantsSolanum lycopersicumTriticum aestivume1
- Interactor
- A. brasilenseAzospirillum brasilensee0symbiont
- Outcome
- Survival of A. brasilensee0
- Setting
- geographical origin of the soile0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Survival of A. brasilense in soils without plants differed from that in the rhizosphere and was mainly related to the geographical origin of the soil.”
e1“rhizosphere of wheat and tomato plants”
Claim · model-written summary
Azospirillum viability in Israeli soils declined rapidly or disappeared within 35 days.
- Outcome
- viability of A. brasilensee0
- Direction
- rapidly declinede0
- Value
- 35 dayse0
- Setting
- Israeli soils from arid, semiarid, or mountain regionse0
Not reportedTaxon
Verbatim
e0“In Israeli soils from arid, semiarid, or mountain regions, viability of A. brasilense rapidly declined or populations completely disappeared below detectable levels within 35 days after inoculation.”
Claim · model-written summary
Azospirillum populations remained stable or rose in arid Baja California Sur soils over 45 days.
- Outcome
- populationse0
- Direction
- remained stable or even increasede0
- Value
- 45-day periode0
- Setting
- Baja California Sur, Mexicoe0
Not reportedTaxon
Verbatim
e0“populations in the arid soils of Baja California Sur, Mexico, remained stable or even increased during the 45-day period after inoculation.”
Claim · model-written summary
Azospirillum viability slowly declined in Central Mexican soils.
Not reportedTaxon
Verbatim
e0“In soils from Central Mexico, viability slowly decreased with time.”
Claim · model-written summary
Clay, nitrogen, organic matter and water holding capacity correlated positively with bacterial viability.
Not reportedTaxon
Verbatim
e0“percentages of clay, nitrogen, organic matter, and water-holding capacity were positively correlated with bacterial viability.”
Claim · model-written summary
Calcium carbonate and sand percentages negatively affected bacterial viability.
Not reportedTaxon
Verbatim
e0“High percentages of CaCO(inf3) and fine or rough sand had a highly negative effect on viability.”
Claim · model-written summary
Silt, pH, phosphorus, potassium, conductivity and C/N ratio had no apparent effect on bacterial viability.
Not reportedTaxon
Verbatim
e0“The percentage of silt, pH, the percentage of phosphorus or potassium, electrical conductivity, and C/N ratio had no apparent effect on bacterial viability in the soil.”
Claim · model-written summary
After inoculated plants were removed, bacterial populations declined sharply and became undetectable by day 90.
- Taxon
- wheat and tomato plantsSolanum lycopersicumTriticum aestivume1
- Treatment
- removal of inoculated plantse0
- Interactor
- bacterial populatione0symbiont
- Outcome
- remaining bacterial populatione0
- Direction
- decline sharplye0
- Value
- 90 dayse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Fifteen days after removal of inoculated plants, the remaining bacterial population in the three soil types tested began to decline sharply, reaching undetectable levels 90 days after inoculation.”
e1“rhizosphere of wheat and tomato plants”
Claim · model-written summary
Water percolation after plant removal almost eliminated Azospirillum.
- Taxon
- wheat and tomato plantsSolanum lycopersicumTriticum aestivume1
- Treatment
- percolating the soils with watere0
- Interactor
- A. brasilenseAzospirillum brasilensee0symbiont
- Outcome
- A. brasilense populatione0
- Direction
- almost eliminatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After plant removal, percolating the soils with water almost eliminated the A. brasilense population.”
e1“rhizosphere of wheat and tomato plants”
Claim · model-written summary
Azospirillum viability was almost identical in artificial and corresponding natural Israeli soils.
Not reportedTaxon
Verbatim
e0“Viability of A. brasilense in two artificial soils containing the same major soil components as the natural soils from Israel did was almost identical to that in the natural soils.”
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See all 65 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.