Abstract
The effects of the foliar application of phytocidal concentrations of 2-methyl-4-chlorophenoxyacetic acid (MCPA) on change in total dry weight, and in ‘available carbohydrate’ (starch, ‘total’ and ‘reducing’ sugars), total nitrogen, phosphorus, potassium, calcium, and magnesium of ‘tops’ and roots of tomato plants have been followed over a period of 14 days following spraying. There were two main treatments—‘nutrient’ (nutrient supply to roots continued after spraying) and ‘water’ (distilled water only supplied to roots after spraying) and ‘water’ (distilled water only supplied to roots after spraying)—the sub-treatments consisting of ‘MCPA’ versus ‘no-MCPA’ for each of the main treatments. Twelve different times of sampling were used. In analysing the present data, the quantity ‘residual dry weight’ (total dry weight less ‘available carbohydrate’), which was originally introduced by Mason and Maskell as a basis of reference for analyses of plant organs in short-period experiments not involving appreciable growth, has been used as an estimate of the permanent structure of plant growth. This new use of the ‘residual dry weight’ basis has brought out important features which were obscured when the data were left in their primary form (as percentages of total dry weight or amounts per plant). Growth, as measured by increase in ‘residual dry weight’, was greatly inhibited by 2-methyl-4-chlorophenoxyacetic acid shortly after spraying, in both the presence and the absence of nutrient. In the presence of 2-methyl-4-chlorophenoxyacetic acid, net assimilation rate (estimated as rate of increase in total dry weight per gram ‘residual dry weight’ of the ‘tops’) was greatly diminished while uptake of total nitrogen and of P2O5 (estimated as increase in total nitrogen or of P2O5 of the whole plant per day per 1 g. ‘residual dry weight’ of the roots) appeared to undergo a similar but much smaller diminution. It seemed probable, however, that in the presence of MCPA a larger proportion of the carbohydrate actually formed was utilized for synthesis of aminoacids and protein. In the plant as a whole there was no evidence of actual depletion of ‘available carbohydrate’ as a result of MCPA treatment, this fraction showing a steady increase in all treatments throughout the experiment. The rate of increase was, however, much reduced by MCPA treatment. The ‘tops’ presented much the same picture as the whole plant, but for the roots the situation was quite different. While the roots of the ‘no-MCPA’ plants and also of the ‘MCPA-water’ plants showed a steady increase in available carbohydrate, those of the ‘MCPA-nutrient’ plants rose only very slightly (from the initial value of 8 mg. per plant to about 10 mg.) during the first 2 days, and then in the next 2 days declined to a value (about 6 mg.) below the initial and remained at this low level for the rest of the experiment. It is suggested that the phytocidal effect of 2-methyl-4-chlorophenoxyacetic acid in the presence of nutrient may be due to depletion of the ‘available carbohydrate’ supplies in the roots, which is shown to be brought about, in part, by reduced transport from the tops, and partly by the relatively greater utilization of the carbohydrate present. These results offer an explanation for the facts that plants showing vigorous growth are more easily killed by MCPA and that perennial plants, particularly those with storage tissues in their roots, are more resistant. Further, they suggest the useful practical application that MCPA treatment should be given when the carbohydrate reserves of the roots are at a minimum. For perennial plants, conditions might be expected to be optimal for the application of MCPA in late spring, at a time when the first ‘flush’ of growth is slowing down and before any appreciable new reserves of carbohydrate have been accumulated. It was also shown that 2-methyl-4-chlorophenoxyacetic acid prevented the net synthesis of starch, but still permitted an appreciable net formation of sucrose. 2-methyl-4-chlorophenoxyacetic acid appeared to have no effect on the uptake of potassium, calcium, or of magnesium. The lack of effect on potassium is contrasted with the previous observation by Rhodes, Templeman, and Thruston (1950) that sub-lethal concentrations of MCPA, applied over a relatively long period to the roots of tomato plants, specifically depressed the uptake of potassium.
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Claims 20
Claim · model-written summary
Residual dry weight revealed features obscured by conventional reporting bases.
- Taxon
- Solanum lycopersicum (Tomato)
Solanum lycopersicumt0 - Outcome
- important featurese0
- Comparator
- percentages of total dry weight or amounts per plante0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This new use of the ‘residual dry weight’ basis has brought out important features which were obscured when the data were left in their primary form (as percentages of total dry weight or amounts per plant).”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
MCPA greatly inhibited tomato growth measured as residual dry weight soon after spraying, with and without nutrients.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Treatment
- 2-methyl-4-chlorophenoxyacetic acide0
- Outcome
- Growth, as measured by increase in ‘residual dry weight’e0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Growth, as measured by increase in ‘residual dry weight’, was greatly inhibited by 2-methyl-4-chlorophenoxyacetic acid shortly after spraying, in both the presence and the absence of nutrient.”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
MCPA greatly diminished tomato net assimilation rate.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Treatment
- 2-methyl-4-chlorophenoxyacetic acide0
- Outcome
- net assimilation ratee0
- Direction
- diminishede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the presence of 2-methyl-4-chlorophenoxyacetic acid, net assimilation rate (estimated as rate of increase in total dry weight per gram ‘residual dry weight’ of the ‘tops’) was greatly diminished”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
MCPA appeared to diminish total nitrogen uptake to a smaller extent.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Treatment
- MCPAe1
- Outcome
- uptake of total nitrogene0
- Direction
- diminutione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“uptake of total nitrogen and of P2O5 (estimated as increase in total nitrogen or of P2O5 of the whole plant per day per 1 g. ‘residual dry weight’ of the roots) appeared to undergo a similar but much smaller diminution.”
t0“Solanum lycopersicum (Tomato)”
e1“in the presence of MCPA a larger proportion of the carbohydrate actually formed was utilized for synthesis of aminoacids and protein.”
Claim · model-written summary
MCPA appeared to diminish P2O5 uptake to a smaller extent.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Treatment
- MCPAe1
- Outcome
- P2O5e0
- Direction
- diminutione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“uptake of total nitrogen and of P2O5 (estimated as increase in total nitrogen or of P2O5 of the whole plant per day per 1 g. ‘residual dry weight’ of the roots) appeared to undergo a similar but much smaller diminution.”
t0“Solanum lycopersicum (Tomato)”
e1“in the presence of MCPA a larger proportion of the carbohydrate actually formed was utilized for synthesis of aminoacids and protein.”
Claim · model-written summary
The authors inferred a larger share of carbohydrate was used for amino-acid and protein synthesis under MCPA.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Treatment
- MCPAe0
- Compound
- carbohydratee0
- Outcome
- synthesis of aminoacids and proteine0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the presence of MCPA a larger proportion of the carbohydrate actually formed was utilized for synthesis of aminoacids and protein.”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
MCPA did not show evidence of depleting whole-plant available carbohydrate.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Treatment
- MCPA treatmente0
- Outcome
- ‘available carbohydrate’e0
- Direction
- no evidence of actual depletione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there was no evidence of actual depletion of ‘available carbohydrate’ as a result of MCPA treatment”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
Available carbohydrate rose steadily in every treatment throughout the experiment.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Outcome
- this fractione0
- Direction
- increasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this fraction showing a steady increase in all treatments throughout the experiment.”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
MCPA greatly reduced the rate of increase in available carbohydrate.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Treatment
- MCPA treatmente0
- Outcome
- rate of increasee0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The rate of increase was, however, much reduced by MCPA treatment.”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
Root available carbohydrate increased steadily without MCPA.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Organ / stage
- rootse0
- Treatment
- ‘no-MCPA’e0
- Outcome
- available carbohydratee0
- Direction
- increasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the roots of the ‘no-MCPA’ plants and also of the ‘MCPA-water’ plants showed a steady increase in available carbohydrate”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
Root available carbohydrate increased steadily under MCPA with water only.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Organ / stage
- rootse0
- Treatment
- ‘MCPA-water’e0
- Outcome
- available carbohydratee0
- Direction
- increasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the roots of the ‘no-MCPA’ plants and also of the ‘MCPA-water’ plants showed a steady increase in available carbohydrate”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
Under MCPA with nutrients, root available carbohydrate rose from 8 to about 10 mg per plant over two days.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Organ / stage
- rootse1
- Treatment
- ‘MCPA-nutrient’e0
- Outcome
- rose only very slightlye0
- Value
- about 10 mg.e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“those of the ‘MCPA-nutrient’ plants rose only very slightly (from the initial value of 8 mg. per plant to about 10 mg.) during the first 2 days”
t0“Solanum lycopersicum (Tomato)”
e1“While the roots of the ‘no-MCPA’ plants”
Claim · model-written summary
Under MCPA with nutrients, root available carbohydrate then fell to about 6 mg and stayed low.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Organ / stage
- rootse1
- Treatment
- MCPAe1
- Outcome
- declined to a valuee0
- Value
- about 6 mg.e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“and then in the next 2 days declined to a value (about 6 mg.) below the initial and remained at this low level for the rest of the experiment.”
t0“Solanum lycopersicum (Tomato)”
e1“the roots of the ‘no-MCPA’ plants and also of the ‘MCPA-water’ plants”
Claim · model-written summary
The authors suggested MCPA phytotoxicity with nutrients may arise from depletion of root available carbohydrate.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Treatment
- 2-methyl-4-chlorophenoxyacetic acide0
- Compound
- ‘available carbohydrate’e0
- Outcome
- phytocidal effecte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the phytocidal effect of 2-methyl-4-chlorophenoxyacetic acid in the presence of nutrient may be due to depletion of the ‘available carbohydrate’ supplies in the roots”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
Reduced transport from tops was proposed as one contributor to root carbohydrate depletion.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Outcome
- reduced transport from the topse0
- Qualifier
- carbohydrate presente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“which is shown to be brought about, in part, by reduced transport from the tops, and partly by the relatively greater utilization of the carbohydrate present.”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
Relatively greater carbohydrate use was proposed as another contributor to depletion.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Compound
- carbohydratee0
- Outcome
- greater utilization of the carbohydrate presente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“which is shown to be brought about, in part, by reduced transport from the tops, and partly by the relatively greater utilization of the carbohydrate present.”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
The authors recommended MCPA when root carbohydrate reserves are minimal.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Outcome
- MCPA treatment should be given when the carbohydrate reserves of the roots are at a minimume0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“MCPA treatment should be given when the carbohydrate reserves of the roots are at a minimum.”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
MCPA prevented net starch synthesis.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Treatment
- 2-methyl-4-chlorophenoxyacetic acide0
- Outcome
- net synthesis of starche0
- Direction
- preventede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“2-methyl-4-chlorophenoxyacetic acid prevented the net synthesis of starch, but still permitted an appreciable net formation of sucrose.”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
MCPA still permitted appreciable net sucrose formation.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Treatment
- 2-methyl-4-chlorophenoxyacetic acide0
- Outcome
- net formation of sucrosee0
- Direction
- appreciablee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“2-methyl-4-chlorophenoxyacetic acid prevented the net synthesis of starch, but still permitted an appreciable net formation of sucrose.”
t0“Solanum lycopersicum (Tomato)”
Claim · model-written summary
MCPA appeared not to affect uptake of potassium, calcium or magnesium.
- Taxon
- Solanum lycopersicum (Tomato)Solanum lycopersicumt0
- Treatment
- 2-methyl-4-chlorophenoxyacetic acide0
- Outcome
- uptake of potassium, calcium, or of magnesiume0
- Direction
- no effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“2-methyl-4-chlorophenoxyacetic acid appeared to have no effect on the uptake of potassium, calcium, or of magnesium.”
t0“Solanum lycopersicum (Tomato)”