Abstract
Abstract. Seedlings of Zea mays L. were grown in the dark at 27°C. Four‐day‐old seedlings were then exposed for 3 days to solutions equilibrated with gas mixtures to give O 2 concentrations between 0.02 and 0.25 mol m −3 . Root growth was impaired just as severely at 0.06 as 0.02 mol O 2 m −3 while growth at 0.16 mol O 2 m −3 was about the same as in solutions in equilibrium with air (0.25 mol O 2 m −3 ). Growth of young seedlings at low O 2 concentrations was inhibited to the same extent in nutrient solution and 0.5 ml m −3 CaCl 2 , showing that the adverse effect of O 2 deficits on growth was not due to less uptake of inorganic nutrients. Furthermore, at low O 2 concentrations neither exposure of the shoots to a relative humidity of 100% (26.0 g H 2 O m −3 ) nor excision of the entire shoot enhanced root growth relative to that in plants with shoots at a relative humidity of 50% (13.0 g H 2 O m −3 ). Therefore, for these seedlings growing in the dark, impairment of root growth at low O 2 concentrations was not a consequence of water deficits in the shoot or of other shoot‐root interactions. Total soluble sugars and amino acid concentrations were generally greater at low (0.02–0.06 mol O 2 m −3 ) than at high O 2 concentrations (0.16–0.25 mol O 2 m −3 ). This applied specifically to the root apices (0–2 mm) and expanding (2–15 mm) tissue except in some experiments where sugar concentrations in expanding tissue were slightly greater at high than at low O 2 concentrations. Critical O 2 pressures for respiration of excised root segments were approximately 0.117 and 0.065 mol O 2 m −3 in the expanding and expanded zones of the roots, respectively. In contrast, the critical O 2 pressure exceeded 0.20 mol O 2 m −3 in the apex, suggesting that O 2 supply for metabolic processes is most likely to be sub‐optimal in this zone. Our results show clearly that the adverse effects of low O 2 concentrations are unlikely to be a consequence of substrate shortage for either respiration or synthesis of macromolecules; low rates of ATP regeneration in growing root tissues are the logical cause for impaired growth in young seedlings while they are being sustained by seed reserves.
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Claims 13
Claim · model-written summary
Root growth was equally impaired at 0.06 and 0.02 mol O 2 m −3.
- Treatment
- 0.06e1
- Outcome
- Root growthe1
- Direction
- impaired just as severelye1
- Comparator
- 0.02 mol O 2 m −3e1
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedlings of Zea mays L.”
e1“Root growth was impaired just as severely at 0.06 as 0.02 mol O 2 m −3”
Claim · model-written summary
Root growth at 0.16 mol O 2 m −3 was similar to growth in air-equilibrated solution.
- Treatment
- 0.16 mol O 2 m −3e1
- Outcome
- growthe1
- Direction
- about the samee1
- Comparator
- solutions in equilibrium with aire1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedlings of Zea mays L.”
e1“growth at 0.16 mol O 2 m −3 was about the same as in solutions in equilibrium with air (0.25 mol O 2 m −3 )”
Claim · model-written summary
Low oxygen inhibited growth equally in nutrient solution and dilute calcium chloride solution.
- Treatment
- low O 2 concentrationse1
- Outcome
- Growth of young seedlingse1
- Direction
- inhibited to the same extente1
- Comparator
- nutrient solution and 0.5 ml m −3 CaCl 2e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedlings of Zea mays L.”
e1“Growth of young seedlings at low O 2 concentrations was inhibited to the same extent in nutrient solution and 0.5 ml m −3 CaCl 2”
Claim · model-written summary
At low oxygen, 100% shoot humidity did not enhance root growth relative to 50% humidity.
- Treatment
- relative humidity of 100%e1
- Outcome
- root growthe1
- Direction
- nore1
- Comparator
- relative humidity of 50%e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedlings of Zea mays L.”
e1“at low O 2 concentrations neither exposure of the shoots to a relative humidity of 100% (26.0 g H 2 O m −3 ) nor excision of the entire shoot enhanced root growth relative to that in plants with shoots at a relative humidity of 50% (13.0 g H 2 O m −3 )”
Claim · model-written summary
At low oxygen, shoot excision did not enhance root growth relative to intact shoots at 50% humidity.
- Treatment
- excision of the entire shoote1
- Outcome
- root growthe1
- Direction
- nore1
- Comparator
- plants with shoots at a relative humidity of 50%e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedlings of Zea mays L.”
e1“at low O 2 concentrations neither exposure of the shoots to a relative humidity of 100% (26.0 g H 2 O m −3 ) nor excision of the entire shoot enhanced root growth relative to that in plants with shoots at a relative humidity of 50% (13.0 g H 2 O m −3 )”
Claim · model-written summary
Total soluble sugars were generally greater at low than high oxygen, particularly in apical and expanding root tissues.
- Organ / stage
- root apicese1
- Treatment
- low (0.02–0.06 mol O 2 m −3 )e1
- Outcome
- Total soluble sugarse1
- Direction
- greatere1
- Comparator
- high O 2 concentrations (0.16–0.25 mol O 2 m −3 )e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedlings of Zea mays L.”
e1“Total soluble sugars and amino acid concentrations were generally greater at low (0.02–0.06 mol O 2 m −3 ) than at high O 2 concentrations (0.16–0.25 mol O 2 m −3 ). This applied specifically to the root apices (0–2 mm) and expanding (2–15 mm) tissue”
Claim · model-written summary
Amino acid concentrations were generally greater at low than high oxygen in root apices and expanding tissue.
- Organ / stage
- root apicese1
- Treatment
- low (0.02–0.06 mol O 2 m −3 )e1
- Outcome
- amino acid concentrationse1
- Direction
- greatere1
- Comparator
- high O 2 concentrations (0.16–0.25 mol O 2 m −3 )e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedlings of Zea mays L.”
e1“Total soluble sugars and amino acid concentrations were generally greater at low (0.02–0.06 mol O 2 m −3 ) than at high O 2 concentrations (0.16–0.25 mol O 2 m −3 ). This applied specifically to the root apices (0–2 mm) and expanding (2–15 mm) tissue”
Claim · model-written summary
In some experiments, expanding-tissue sugars were slightly greater at high oxygen.
- Treatment
- highe1
- Outcome
- sugar concentrations in expanding tissuee1
- Direction
- slightly greatere1
- Comparator
- low O 2 concentrationse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedlings of Zea mays L.”
e1“in some experiments where sugar concentrations in expanding tissue were slightly greater at high than at low O 2 concentrations”
Claim · model-written summary
Critical oxygen pressure for respiration in expanding root segments was approximately 0.117 mol O 2 m −3.
- Organ / stage
- expandinge1
- Outcome
- Critical O 2 pressures for respiration of excised root segmentse1
- Value
- 0.117e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedlings of Zea mays L.”
e1“Critical O 2 pressures for respiration of excised root segments were approximately 0.117 and 0.065 mol O 2 m −3 in the expanding and expanded zones of the roots, respectively.”
Claim · model-written summary
Critical oxygen pressure for respiration in expanded root segments was approximately 0.065 mol O 2 m −3.
- Organ / stage
- expanded zonese1
- Outcome
- Critical O 2 pressures for respiration of excised root segmentse1
- Value
- 0.065 mol O 2 m −3e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedlings of Zea mays L.”
e1“Critical O 2 pressures for respiration of excised root segments were approximately 0.117 and 0.065 mol O 2 m −3 in the expanding and expanded zones of the roots, respectively.”
Claim · model-written summary
Critical oxygen pressure in the apex exceeded 0.20 mol O 2 m −3.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedlings of Zea mays L.”
e1“the critical O 2 pressure exceeded 0.20 mol O 2 m −3 in the apex”
Claim · model-written summary
The authors inferred that oxygen supply to metabolic processes was most likely suboptimal in root apices.
- Organ / stage
- apexe2
- Outcome
- O 2 supply for metabolic processese1
- Qualifier
- most likely to be sub‐optimale1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedlings of Zea mays L.”
e1“O 2 supply for metabolic processes is most likely to be sub‐optimal in this zone”
e2“in the apex”
Claim · model-written summary
The authors concluded that low ATP regeneration in growing roots caused impaired growth under low oxygen.
- Outcome
- impaired growth in young seedlingse1
- Qualifier
- low rates of ATP regeneration in growing root tissuese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedlings of Zea mays L.”
e1“low rates of ATP regeneration in growing root tissues are the logical cause for impaired growth in young seedlings while they are being sustained by seed reserves”
The same questions in other papers
humidity · growth · Zea mays (maize)Positive and negative results
3 papers in the same direction as this paper · 1 reporting no difference from an alternative
- positive
- no effect
- negative
1 paper more in this group
See all 5 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.