Abstract
1. The effect of water economy on the plant growth was investigated in young tobacco plants with water level lowering of culture solutions. The 2cm.-, 4cm.-, 6cm.- and 8cm.-sets were prepared.2. The plant growth in dry weight was decreased in proportion to the water level lowering, i. e., the relative values of 100: 87.5: 78.9: 68.6 were observed at the 2cm.-, 4cm.-, 6cm.- and 8cm.-sets, respectively. Also the lowest net assimilation rate (NAR) was obtained at the 8cm.-set.3. The ratio of the dry weight of non-photosynthetic organs to the leaf area indicated no difference among the sets.4. With. lowering the water level, heavy water deficit was induced in leaves, but no deficit was observed in stems and roots. A clear relationship was discovered between the leaf water deficit and the ratio of submerged roots to leaf area (active root/leaf area ratio), which was used here as an indicator of the grade of water level lowering.5. The net assimilation decreased almost linearly with progress of the leaf water deficit, while no change was observed in respiratory activity of leaves as to water deficit and no special depression of nitrogen content in leaves was detected during the experimental period.6. The growth in dry weight at the 2cm.- and 8cm.-sets was calculated theoretically with the net assimilation, which was affected by the leaf water deficit caused by water level lowering. The agreement between the calculated and the observed proves that the primary cause of the growth depression with water level lowering is the suppressed photosynthesis of leaves.
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Claims 10
Claim · model-written summary
Plant dry weight decreased progressively across the 2, 4, 6 and 8 cm sets.
- Taxon
- tobacco plants
Nicotiana tabacume1 - Treatment
- water level loweringe0
- Outcome
- plant growth in dry weighte0
- Direction
- decreasede0
- Value
- 100: 87.5: 78.9: 68.6e0
- Comparator
- 2cm.-e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The plant growth in dry weight was decreased in proportion to the water level lowering, i. e., the relative values of 100: 87.5: 78.9: 68.6 were observed at the 2cm.-, 4cm.-, 6cm.- and 8cm.-sets, respectively.”
e1“young tobacco plants”
Claim · model-written summary
Net assimilation rate was lowest in the 8 cm set.
Not reportedTaxon
Verbatim
e0“the lowest net assimilation rate (NAR) was obtained at the 8cm.-set.”
Claim · model-written summary
The dry weight of nonphotosynthetic organs per leaf area did not differ among sets.
- Outcome
- ratio of the dry weight of non-photosynthetic organs to the leaf areae0
- Direction
- no differencee0
Not reportedTaxon
Verbatim
e0“The ratio of the dry weight of non-photosynthetic organs to the leaf area indicated no difference among the sets.”
Claim · model-written summary
Lower water levels induced heavy leaf water deficit.
Not reportedTaxonComparator
Verbatim
e0“With. lowering the water level, heavy water deficit was induced in leaves”
Claim · model-written summary
No water deficit was observed in stems or roots.
Not reportedTaxon
Verbatim
e0“but no deficit was observed in stems and roots.”
Claim · model-written summary
Leaf water deficit related to submerged-root area per leaf area.
Not reportedTaxonDirection
Verbatim
e0“A clear relationship was discovered between the leaf water deficit and the ratio of submerged roots to leaf area (active root/leaf area ratio)”
Claim · model-written summary
Net assimilation declined almost linearly as leaf water deficit progressed.
Not reportedTaxon
Verbatim
e0“The net assimilation decreased almost linearly with progress of the leaf water deficit”
Claim · model-written summary
Leaf respiratory activity showed no change with water deficit.
Not reportedTaxon
Verbatim
e0“no change was observed in respiratory activity of leaves as to water deficit”
Claim · model-written summary
Leaf nitrogen content showed no special depression.
Not reportedTaxon
Verbatim
e0“no special depression of nitrogen content in leaves was detected during the experimental period.”
Claim · model-written summary
Calculated and observed growth agreed, supporting suppressed leaf photosynthesis as the primary cause of growth depression.
- Treatment
- water level loweringe0
- Outcome
- growth depressione0
- Qualifier
- suppressed photosynthesis of leavese0
Not reportedTaxon
Verbatim
e0“The agreement between the calculated and the observed proves that the primary cause of the growth depression with water level lowering is the suppressed photosynthesis of leaves.”