Abstract
Abstract The utilization of plant‐ and soil‐C by the microbial biomass in the rhizosphere of maize plants was investigated as a function of root proximity. The plants were cultivated in pots with divided root chambers and their shoots supplied with 14 CO 2 for 23 days. Subsequently the individual soil zones were analyzed for organic C, 14 C, biomass C and biomass 14 C. Plant roots induced a 197% increase in microbial biomass and a 5.4% decrease in soil organic C compared with an 1.2% decrease in the unplanted control soil. The contributions of plant‐ and soil‐C to this increased microbial growth amounted to 68% and 32% respectively. Biomass‐ 14 C corresponded to 1.6% of the total photosynthetically fixed 14 C, to about 15% of the organic 14 C‐input into the rhizosphere and to 58% of the plant carbon remaining in soil after the removal of roots. 20% of this biomass‐ 14 C was found outside the immediate root zone. These results demonstrate that growing roots are a significant C‐source for the microbial biomass and render an additional fraction of soil‐C available to microbial utilization. The efficiency of C‐utilization by the rhizosphere biomass is lower than values obtained with liquid cultures in laboratory experiments. The supply of plant‐C to the microbial biomass outside the immediate root vicinity indicates that the overall volume of the maize rhizosphere is greater than what has been supposed so far.
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Claims 9
Claim · model-written summary
Maize roots induced a 197% increase in microbial biomass relative to unplanted soil.
- Treatment
- Plant rootse1
- Outcome
- microbial biomasse1
- Direction
- increasee1
- Value
- 197%e1
- Comparator
- unplanted control soile1
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the rhizosphere of maize plants”
e1“Plant roots induced a 197% increase in microbial biomass and a 5.4% decrease in soil organic C compared with an 1.2% decrease in the unplanted control soil”
Claim · model-written summary
Maize roots caused a 5.4% decrease in soil organic C, compared with a 1.2% decrease in unplanted soil.
- Treatment
- Plant rootse1
- Outcome
- soil organic Ce1
- Direction
- decreasee1
- Value
- 5.4%e1
- Comparator
- unplanted control soile1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the rhizosphere of maize plants”
e1“Plant roots induced a 197% increase in microbial biomass and a 5.4% decrease in soil organic C compared with an 1.2% decrease in the unplanted control soil”
Claim · model-written summary
Plant-derived carbon accounted for 68% of the increased microbial growth in the maize rhizosphere.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the rhizosphere of maize plants”
e2“to this increased microbial growth amounted to 68% and 32% respectively”
Claim · model-written summary
Soil-derived carbon accounted for 32% of the increased microbial growth in the maize rhizosphere.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the rhizosphere of maize plants”
e2“to this increased microbial growth amounted to 68% and 32% respectively”
Claim · model-written summary
Microbial biomass 14C corresponded to 1.6% of the total photosynthetically fixed 14C.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the rhizosphere of maize plants”
e3“corresponded to 1.6% of the total photosynthetically fixed 14 C”
Claim · model-written summary
Microbial biomass 14C was about 15% of the organic 14C input into the rhizosphere.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the rhizosphere of maize plants”
e4“to about 15% of the organic 14 C”
Claim · model-written summary
About 58% of the plant carbon remaining in soil after root removal was found in microbial biomass.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the rhizosphere of maize plants”
e5“to 58% of the plant carbon remaining in soil after the removal of roots”
Claim · model-written summary
About 20% of the microbial biomass 14C was found outside the immediate root zone.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the rhizosphere of maize plants”
e6“20% of this biomass‐ 14 C was found outside the immediate root zone”
Claim · model-written summary
The efficiency of C utilization by rhizosphere biomass is lower than in liquid laboratory cultures.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the rhizosphere of maize plants”
e7“The efficiency of C‐utilization by the rhizosphere biomass is lower than values obtained with liquid cultures in laboratory experiments”