The DOI matches its Crossref record; 20 of the 20 references it cites were found in a registry or an index; none of the 18 sources its claims cite is checked for support yet.
The effect of herbicides on the rates of photosynthesis and respiration in spinach leaves.
Open accessAbstract
The effect of addition of herbicides or insecticide to the rate of photosynthesis or respiration in spinach leaf discs was studied. Spinach leaf discs floated in an illuminated bicarbonate solution as they photosynthesized and generated oxygen and sank in the dark as they respired and consumed oxygen. The rates of photosynthesis and respiration were calculated from the time for 50% of the leaf discs to float or to sink respectively. The ratio of the photosynthesis rate to the respiration rate (P/R) in the presence of different herbicides was calculated and compared against the control. It was found that a P/R rate < control was indicative of the herbicide disrupting electron transfer in Photosystem II or I upstream of the Calvin cycle, whereas a P/R > control was indicative of redox disruption in the mitochondrial electron transfer chain, the shikimate pathway or at sites downstream of the Calvin cycle. The magnitude of the P/R ratio to the control can potentially accurately determine the site of action of a particular herbicide on photoautotrophic organisms.
Overview
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TL;DR
Using the spinach leaf-disc floatation/sinking assay, this study found that herbicide/insecticide exposure significantly altered the photosynthesis-to-respiration (P/R) ratio. The direction of change was interpreted as indicating whether a compound disrupts light reactions (P/R below control) or dark reactions/downstream pathways (P/R above control).
Key findings
- Control P/R was 2.69 ± 1.34. KnockOut (glyphosate isopropylamine) gave P/R = 23.35 ± 3.83 and Triazide (gamma-cyhalothrin) gave P/R = 28.63 ± 2.46, both significantly higher than control (p = 0.001 and p = 0.0001, respectively). Spectracide (diquat dibromide, fluazifop-p-butyl, dicamba dimethylamine) gave P/R = 0.44 ± 0.18, significantly lower than control (p = 0.024).
- KnockOut and Triazide P/R ratios were not significantly different from each other (p = 0.076).
- The paper interprets P/R < control as disruption of electron transfer before CO2 fixation (light reactions), and P/R > control as disruption of CO2 fixation pathways, TCA cycle, mitochondrial ETC, or shikimic acid pathways downstream of the Calvin cycle.
- Diquat-containing Spectracide at sublethal dilution >1100× had P/R below control; at dilutions <1000×, leaf discs did not photosynthesize/float. Gamma-cyhalothrin was predicted to modulate CO2 fixation downstream of the Calvin cycle, similar to glyphosate, and is known to inhibit mitochondrial complex I.
Methods
- Leaf-disc assay: spinach leaves from grocery stores were stored at 4–8 °C and used within 2 weeks. Ten leaf discs were punched, vacuum-infiltrated with citrate-phosphate buffer or herbicide/insecticide solution plus dish soap, then placed in 0.22% sodium bicarbonate; illuminated with a 40 W incandescent bulb at <2 cm; time to float (ET50L) was recorded, then dark time to sink (ET50D).
- Rates were calculated as photosynthesis = 1/ET50L + 1/ET50D and respiration = 1/ET50D; the P/R ratio was then calculated. Chlorophyll absorbance was measured spectrophotometrically, and light intensity, pH, and temperature were monitored.
- Analysis used independent two-tailed unpaired Student’s t tests comparing P/R ratios, with significance at p < 0.05. Table 3 concentrations were glyphosate 8.4 × 10⁻² M, diquat 3.17 × 10⁻⁶ M, fluazifop-p-butyl 1.42 × 10⁻⁶ M, dicamba 1.36 × 10⁻⁶ M, and gamma-cyhalothrin 1.78 × 10⁻³ M; Spectracide was diluted 1100×.
Limitations
- Paper-stated: the number of compounds tested was small, and more comprehensive studies and more compounds with known mechanisms of action are needed to validate P/R as a predictor of site of action.
- Paper-stated: herbicide concentrations differed by orders of magnitude, so concentration effects could contribute; the concentration-to-LD50 ratio was used as a first approximation, with glyphosate and gamma-cyhalothrin treated as equi-lethal, while Spectracide required 1100× dilution.
- Evident from the text: pH of the media ranged from 6.5 to 7.7, changing the calculated [HCO3⁻]/[CO2] ratio from 2.5 to 39.8, which could affect photosynthesis; the number of independent replicates for the P/R measurements is not reported.
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Integrity signals
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Claims the paper makes
0 Valid · 0 Not valid · 14 Not checked · 37 Own results and interpretations
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“As can be seen from table 3, the R/P ratio for the control is 0.37.”
§ The effect of herbicides on the rates of photosynthesis and respiration in in spinach leaves > Figure 7: Standard curve for chlorophyll at 440 and 660 nm
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A result the paper states — it cites no source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“There are hence 3.38 x 10 17 photons impinging on the tube per cm 2 .s.”
§ The effect of herbicides on the rates of photosynthesis and respiration in in spinach leaves > Results and discussion
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The herbicides and the insecticide significantly altered the P/R ratio of the spinach leaves.”
§ The effect of herbicides on the rates of photosynthesis and respiration in in spinach leaves > Abstract
plainstates a cause- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A result the paper states — it cites no source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The pH of the herbicide/insecticide and bicarbonate medium in which the spinach leaves were submerged ranged from 6.5 to 7.7.”
§ The effect of herbicides on the rates of photosynthesis and respiration in in spinach leaves > Figure 7: Standard curve for chlorophyll at 440 and 660 nm
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A result the paper states — it cites no source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“On the other hand, the herbicide (Spectracide) containing diaquat and fluazifop-p-butyl needed to be diluted 1100X in order to decrease lethality to an extent to obtain floatation.”
§ The effect of herbicides on the rates of photosynthesis and respiration in in spinach leaves > Figure 7: Standard curve for chlorophyll at 440 and 660 nm
plainstates a cause- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
19 more claims
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- It may state two separate claims as one. 22
- Probably not a substantial claim. 10
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
Each contradiction between two passages listed here was confirmed by an independent check.
Rated major: it would touch a result — a value a result rests on, reported and recomputed p-values on opposite sides of the significance level, two passages that conflict with no sign which is right, or a cited work retracted before this paper was published.
In the paper
§ The effect of herbicides on the rates of photosynthesis and respiration in in spinach leaves > Rate of photosynthesis = [1/ET50L] + [1/ET50D] equation 1
“Rate of photosynthesis = [1/ET50L] + [1/ET50D] equation 1”
§ The effect of herbicides on the rates of photosynthesis and respiration in in spinach leaves > Conclusions
“| Spectracide TM | | 7.72 | 14.67 ± 0.73 | 6.5 ± 3.54 | 7.94 | 17.92 | 0.44 ± 0.18 |”
Rated minor: it would not touch a result — a value no result rests on, a p-value that stays on the same side of the significance level, or a conflict that is clerical, resolved elsewhere in the paper, or outside its own findings.
In the paper
“the concentration of chlorophyll in 10 leaf discs was calculated to be 7.16 սM or 0.64 mg mL -1 using a molar mass of chlorophyll of 893.51 g mol -1 .”
§ The effect of herbicides on the rates of photosynthesis and respiration in in spinach leaves > Absroption spectrum of chlorophyll
Reported 0.64 · recomputed 0.006398
Rated minor: it would not touch a result — a value no result rests on, a p-value that stays on the same side of the significance level, or a conflict that is clerical, resolved elsewhere in the paper, or outside its own findings.
In the paper
§ The effect of herbicides on the rates of photosynthesis and respiration in in spinach leaves > Results and discussion
“The average weight of a leaf disc was 0.061 g ± 0.86% (average mass ± % relative standard deviation) (n=10, leaf discs weighed=10).”
§ The effect of herbicides on the rates of photosynthesis and respiration in in spinach leaves > Conclusions
“| 1 | Average weight of 10 punched leaves (g) | 0.061 | | 2 | Average weight of 1 punched leaf (g) | [(row1)/10] = | | | | 0.0061 |”
Citations
Cites
The publisher hasn’t deposited this paper’s reference list.
Research works printed but not linked: 3
- Huner NPA, Oquist G, Sarhan F, Energy balance and acclimation to light and cold, Trends in plant sci., 3(6), 224-230, 1998.
- Siehl D, Inhibitors of EPSPS synthase, glutamine synthetase and histidine synthesis. In Roe R, Burton J, Kuhr R, eds. Herbicide activity: toxicology, biochemistry and molecular biology . Amsterdam: IOS Press, 37-67.
- Ashton FM, Crafts AS, 1981, Mode of action of Herbicides, 2 nd ed., New York, John Wiley and Sons.
Cited by
Bicarbonate Toxicity and Elevated pH in Plants: Metabolism, Regulation and Tolerance
Dolui, D., Saha, I., Sarkar, B., Ghosh, A., & Adak, M. K. (2021) · Springer eBooks · doi:10.1007/978-981-15-6221-1_5 · Cited by 7
Ali, M. A., Khan, M. A., & Rao, A. Q. (2024) · International Journal of Phytopathology · doi:10.33687/phytopath.013.01.5127 · Cited by 2
Metadata
- Authors
- Zemedkun, D., Alaparmak, H., & Apte, S.
- Affiliations
- Harmony Science Academy, Euless, TX 76040
- ORCID
- Apte, Shireesh
- Venue
- Journal of High School Science
- Publisher
- Journal of High School Science
- Published
- 2019-02-16
- Volume
- 3
- Issue
- 1
- Pages
- 7518
- ISSN
- 2575-6206 (ISSN-L)
- OpenAlex
- W2951851037
- Semantic Scholar
- 73eddff6742b0c41f1d57efb7ae35108592b3577
- Cited by
- 2
- References
- 0
- Citations by year
- 2024: 1 · 2021: 1
- FWCI
- 0.07
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Journal of High School Science (publishedVersion)
- Topics
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Photosynthetic Processes and Mechanisms
- Life Sciences › Agricultural and Biological Sciences › Plant Science › Weed Control and Herbicide Applications
- Physical Sciences › Environmental Science › Pollution › Pesticide and Herbicide Environmental Studies
- Keywords
- herbicides, photosynthesis, respiration, spinach, leaf discs, photosynthesis to respiration ratio, electron transfer, photosystem II, photosystem I, Calvin cycle, mitochondrial electron transport chain, shikimate pathway, insecticides
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