Abstract
Experiments are described in which the normal geotropic responses of the roots of Pisum sativum seedlings have been compared with those obtained in the presence of auxins (indole-3-acetic acid and 2:4-dichlorophenoxyacetic acid) in the external medium. The courses of positive curvature resulting from short exposures (40 minutes) and also subsequent recovery phenomena on a horizontal klinostat have been followed. A photographic recording technique allowed the determination of absolute growth-rates of both upper and lower sides of the root during the course of each experiment. Positive curvature started at its maximum rate (0.30–0.32 deg./min.) after a reaction time of 11.5 minutes and continued constant at that rate for about 60 minutes after stimulation ceased. Recovery took place at a similar rate of curvature and was complete after a further 150–200 minutes. During the phase of positive curvature overall root growth-rates were considerably reduced and were slowly restored to normal during recovery. Low concentrations (1 part in 10 11 ) of both auxins increased the rate of positive curvature by 30–40 per cent. and shortened the reaction time roughly in proportion. The growth-rates of both sides of the root were increased to the same extent during both curvature and recovery. High concentrations (10 −8 IAA and 3.10 −8 2: 4-D) reduced the rates of curvature by 50 per cent., lengthened the reaction time, and inhibited the growth of both sides of the root during both curvature and recovery. Neither concentration of either auxin otherwise affected the time course of response and recovery. It is suggested that geotropic response is due to the de novo production of an endogenous inhibitor in the extending cells of the lower side of the root whence it may later spread to the upper side. The complete independence of the growth actions of this inhibitor and of the applied auxins suggests that it is not indole-3-acetic acid or any similar compound. Recovery may be very largely independent of both inhibitor and auxins and due to the action of another growth factor limiting cell length. The implications of these findings and of the attendant theories are fully discussed.
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Claims 14
Claim · model-written summary
Positive curvature started at a maximum rate of 0.30–0.32 deg./min.
- Taxon
- Pisum sativum
Lathyrus oleraceuse0 - Outcome
- maximum ratee1
- Value
- 0.30–0.32 deg./min.e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots of Pisum sativum seedlings”
e1“Positive curvature started at its maximum rate (0.30–0.32 deg./min.) after a reaction time of 11.5 minutes and continued constant at that rate for about 60 minutes after stimulation ceased”
Claim · model-written summary
Positive curvature had a reaction time of 11.5 minutes.
- Taxon
- Pisum sativumLathyrus oleraceuse0
- Outcome
- reaction timee1
- Value
- 11.5 minutese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots of Pisum sativum seedlings”
e1“Positive curvature started at its maximum rate (0.30–0.32 deg./min.) after a reaction time of 11.5 minutes and continued constant at that rate for about 60 minutes after stimulation ceased”
Claim · model-written summary
Recovery was complete after a further 150–200 minutes at a similar rate of curvature.
- Taxon
- Pisum sativumLathyrus oleraceuse0
- Outcome
- Recoverye2
- Value
- 150–200 minutese2
- Qualifier
- similar rate of curvaturee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots of Pisum sativum seedlings”
e2“Recovery took place at a similar rate of curvature and was complete after a further 150–200 minutes”
Claim · model-written summary
Overall root growth-rates were reduced during the phase of positive curvature.
- Taxon
- Pisum sativumLathyrus oleraceuse0
- Outcome
- overall root growth-ratese3
- Direction
- reducede3
- Qualifier
- During the phase of positive curvaturee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots of Pisum sativum seedlings”
e3“During the phase of positive curvature overall root growth-rates were considerably reduced and were slowly restored to normal during recovery”
Claim · model-written summary
Low concentrations of both auxins increased the rate of positive curvature by 30–40 per cent.
- Taxon
- Pisum sativumLathyrus oleraceuse0
- Treatment
- Low concentrationse4
- Outcome
- rate of positive curvaturee4
- Direction
- increasede4
- Value
- 30–40 per cente4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots of Pisum sativum seedlings”
e4“Low concentrations (1 part in 10 11 ) of both auxins increased the rate of positive curvature by 30–40 per cent”
Claim · model-written summary
Low concentrations of both auxins shortened the reaction time roughly in proportion.
- Taxon
- Pisum sativumLathyrus oleraceuse0
- Treatment
- Low concentrationse4
- Outcome
- reaction timee5
- Direction
- shortenede5
- Qualifier
- roughly in proportione5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots of Pisum sativum seedlings”
e4“Low concentrations (1 part in 10 11 ) of both auxins increased the rate of positive curvature by 30–40 per cent”
e5“shortened the reaction time roughly in proportion”
Claim · model-written summary
Low concentrations of both auxins increased growth-rates of both sides of the root to the same extent.
- Taxon
- Pisum sativumLathyrus oleraceuse0
- Treatment
- Low concentrationse4
- Outcome
- growth-rates of both sides of the roote6
- Direction
- increasede6
- Qualifier
- to the same extente6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots of Pisum sativum seedlings”
e4“Low concentrations (1 part in 10 11 ) of both auxins increased the rate of positive curvature by 30–40 per cent”
e6“The growth-rates of both sides of the root were increased to the same extent during both curvature and recovery”
Claim · model-written summary
High concentrations of both auxins reduced the rates of curvature by 50 per cent.
- Taxon
- Pisum sativumLathyrus oleraceuse0
- Treatment
- High concentrationse7
- Outcome
- rates of curvaturee7
- Direction
- reducede7
- Value
- 50 per cente7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots of Pisum sativum seedlings”
e7“High concentrations (10 −8 IAA and 3.10 −8 2: 4-D) reduced the rates of curvature by 50 per cent”
Claim · model-written summary
High concentrations of both auxins lengthened the reaction time.
- Taxon
- Pisum sativumLathyrus oleraceuse0
- Treatment
- High concentrationse7
- Outcome
- reaction timee6
- Direction
- lengthenede6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots of Pisum sativum seedlings”
e7“High concentrations (10 −8 IAA and 3.10 −8 2: 4-D) reduced the rates of curvature by 50 per cent”
e6“lengthened the reaction time, and inhibited the growth of both sides of the root during both curvature and recovery”
Claim · model-written summary
High concentrations of both auxins inhibited the growth of both sides of the root.
- Taxon
- Pisum sativumLathyrus oleraceuse0
- Treatment
- High concentrationse7
- Outcome
- growth of both sides of the roote6
- Direction
- inhibitede6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots of Pisum sativum seedlings”
e7“High concentrations (10 −8 IAA and 3.10 −8 2: 4-D) reduced the rates of curvature by 50 per cent”
e6“lengthened the reaction time, and inhibited the growth of both sides of the root during both curvature and recovery”
Claim · model-written summary
Neither auxin concentration otherwise affected the time course of response and recovery.
- Taxon
- Pisum sativumLathyrus oleraceuse0
- Treatment
- Neither concentration of either auxine7
- Outcome
- time course of response and recoverye7
- Direction
- no_changeinferrede7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots of Pisum sativum seedlings”
e7“Neither concentration of either auxin otherwise affected the time course of response and recovery”
Claim · model-written summary
Geotropic response is suggested to be due to de novo production of an endogenous inhibitor.
- Taxon
- Pisum sativumLathyrus oleraceuse0
- Outcome
- geotropic responsee7
- Qualifier
- de novo production of an endogenous inhibitore7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots of Pisum sativum seedlings”
e7“It is suggested that geotropic response is due to the de novo production of an endogenous inhibitor in the extending cells of the lower side of the root”
Claim · model-written summary
The inhibitor is suggested not to be indole-3-acetic acid or any similar compound.
- Taxon
- Pisum sativumLathyrus oleraceuse0
- Outcome
- growth actions of this inhibitore7
- Qualifier
- not indole-3-acetic acid or any similar compounde7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots of Pisum sativum seedlings”
e7“The complete independence of the growth actions of this inhibitor and of the applied auxins suggests that it is not indole-3-acetic acid or any similar compound”
Claim · model-written summary
Recovery may be largely independent of the inhibitor and auxins and due to another growth factor limiting cell length.
- Taxon
- Pisum sativumLathyrus oleraceuse0
- Outcome
- Recoverye7
- Qualifier
- another growth factor limiting cell lengthe7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“roots of Pisum sativum seedlings”
e7“Recovery may be very largely independent of both inhibitor and auxins and due to the action of another growth factor limiting cell length”