Abstract
Transgenic, glyphosate-resistant (GR) cotton has been available to U.S. growers since 1997. Despitewide-spread acceptance, there have been performance complaints by growers citing lower boll retention in GRvarieties than in conventional varieties. Field and greenhouse studies confirmed grower observations,demonstrating a glyphosate-associated decrease in boll retention compared to non-treated GR or conventionalplants. Late (beyond the 5 leaf stage) foliar applications were the most injurious, presumably because plantswere entering early reproductive stages. Boll 'cavitation,' (dessicated bolls attached to plants) also observed bygrowers following glyphosate treatment, resulted from abnormal abscission zone formation and was related tovariety. 14C-glyphosate absorption per square centimeter was greater when applied to stem tissue than leaf tissue, but overallabsorption is likely greater when applied foliarly, due to a greater total surface area. Because glyphosatetypically moves from source tissue to sink tissue, up to 3.7% of applied 14C-glyphosate was translocated toreproductive tissues. Seedling development in both GR and conventional cotton was inhibited by root-absorbed glyphosate.Root tissues were more sensitive to glyphosate than cotyledons or hypocotyls, as was demonstrated byinhibition of lateral root formation and shikimic acid accumulation. CP4-EPSPS content was significantly lowerin GR seedling roots than cotyledons, accounting for glyphosate sensitivity. Further studies compared the accumulation of shikimic acid in response to glyphosate in reproductiveand vegetative tissues in GR and conventional cotton. Shikimic acid accumulation per mM of glyphosate, wasgreater in reproductive than vegetative leaf tissue in both GR and conventional cotton, suggesting thatreproductive tissue is innately more sensitive to glyphosate than vegetative tissue. The quantity of theglyphosate-resistant CP4-EPSPS enzyme was significantly less in stamens than in vegetative leaf tissues.Several morphological differences were apparent in flowers of glyphosate-treated GR cotton. Glyphosate applications inhibited stamen elongation, resulting in anthers not extending to the tip of the stigma,thereby limiting pollen deposition to the lower, less receptive portion of the stigma. Total pollen deposition on the stigma was less in glyphosate-treated GR cotton than non-treated GR or conventional cotton. Microscopicanalysis of pollen revealed that glyphosate arrested maturation in at least 3 pollen developmental stages. Atanthesis, pollen grains from glyphosate-treated GR plants were collapsed, highly vacuolated, and had 60% lowerviability (ability to germinate) than pollen from non-treated GR or conventional plants. Retained bolls fromglyphosate-treated plants had fewer seeds than those from non-treated GR or conventional plants. Hand crossesbetween glyphosate-treated plants demonstrated that the number of seeds per boll was decreased when the maleparent, but not the female parent, was glyphosate treated. Hand pollinations using pollen from treated plants,although overcoming the increased anther-stigma distance, did not restore the normal number of seeds per boll.Treatment of GA onto glyphosate-treated GR plants did not remediate glyphosate effects on pollen viability andfloral morphology. Therefore, presumably, several of the bolls that were shed due to glyphosate-treatments,contained an insufficient number of fertilized ovules and are thus shed. This research proposes that boll shed due to glyphosate in GR cotton is due to insufficient levels ofCP4-EPSPS in stamens, which are highly sensitive to glyphosate. As glyphosate accumulates in reproductivestructures, stamen elongation and pollen development are inhibited, resulting in poor fertilization of ovules. Because fewer ovules are fertilized, bolls are either shed or contain fewer seeds if retained. Growers shouldlimit glyphosate contact with GR cotton, especially during the reproductive stages in order to minimize thepotential for glyphosate-induced boll shed.
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Claims 20
Claim · model-written summary
Glyphosate reduced boll retention relative to untreated resistant or conventional cotton.
- Taxon
- Cotton
Gossypium hirsutumt0 - Treatment
- glyphosatee0
- Outcome
- boll retentione0
- Direction
- decreasee0
- Comparator
- non-treated GR or conventionalplantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a glyphosate-associated decrease in boll retention compared to non-treated GR or conventionalplants.”
t0“Cotton”
Claim · model-written summary
Foliar treatment after the five-leaf stage was most injurious.
- Taxon
- CottonGossypium hirsutumt0
- Treatment
- Late (beyond the 5 leaf stage) foliar applicationse0
- Outcome
- most injuriouse0
- Direction
- most injuriouse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Late (beyond the 5 leaf stage) foliar applications were the most injurious”
t0“Cotton”
Claim · model-written summary
Boll cavitation resulted from abnormal abscission zone formation and varied by variety.
- Taxon
- CottonGossypium hirsutumt0
- Material
- varietye0
- Outcome
- Boll 'cavitation,'e0
- Qualifier
- abnormal abscission zone formatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Boll 'cavitation,' (dessicated bolls attached to plants) also observed bygrowers following glyphosate treatment, resulted from abnormal abscission zone formation and was related tovariety.”
t0“Cotton”
Claim · model-written summary
Glyphosate absorption per square centimeter was greater through stems than leaves.
- Taxon
- CottonGossypium hirsutumt0
- Organ / stage
- stem tissuee0
- Outcome
- 14C-glyphosate absorption per square centimetere0
- Direction
- greatere0
- Comparator
- leaf tissuee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“14C-glyphosate absorption per square centimeter was greater when applied to stem tissue than leaf tissue”
t0“Cotton”
Claim · model-written summary
Up to 3.7% of applied glyphosate reached reproductive tissues.
- Taxon
- CottonGossypium hirsutumt0
- Outcome
- 14C-glyphosate was translocated toreproductive tissuese0
- Value
- 3.7%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“up to 3.7% of applied 14C-glyphosate was translocated toreproductive tissues.”
t0“Cotton”
Claim · model-written summary
Root-absorbed glyphosate inhibited seedling development in resistant and conventional cotton.
- Taxon
- cottonGossypium hirsutume0
- Treatment
- root-absorbed glyphosatee0
- Outcome
- Seedling developmente0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedling development in both GR and conventional cotton was inhibited by root-absorbed glyphosate.”
Claim · model-written summary
Root tissues were more glyphosate-sensitive than cotyledons or hypocotyls.
- Taxon
- CottonGossypium hirsutumt0
- Organ / stage
- Root tissuese0
- Outcome
- sensitive to glyphosatee0
- Direction
- more sensitivee0
- Comparator
- cotyledons or hypocotylse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Root tissues were more sensitive to glyphosate than cotyledons or hypocotyls”
t0“Cotton”
Claim · model-written summary
Glyphosate inhibited lateral root formation.
- Taxon
- CottonGossypium hirsutumt0
- Outcome
- lateral root formatione0
- Direction
- inhibitione0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“inhibition of lateral root formation and shikimic acid accumulation.”
t0“Cotton”
Claim · model-written summary
Glyphosate caused shikimic acid accumulation in roots.
- Taxon
- CottonGossypium hirsutumt0
- Outcome
- shikimic acid accumulatione0
- Direction
- accumulatione0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“inhibition of lateral root formation and shikimic acid accumulation.”
t0“Cotton”
Claim · model-written summary
CP4-EPSPS content was significantly lower in resistant seedling roots than cotyledons.
- Taxon
- CottonGossypium hirsutumt0
- Organ / stage
- GR seedling rootse0
- Gene
- CP4-EPSPSe0
- Outcome
- CP4-EPSPS contente0
- Direction
- lowere0
- Comparator
- cotyledonse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CP4-EPSPS content was significantly lowerin GR seedling roots than cotyledons”
t0“Cotton”
Claim · model-written summary
Shikimic acid accumulated more per unit glyphosate in reproductive than vegetative leaf tissue.
- Taxon
- cottonGossypium hirsutume0
- Organ / stage
- reproductivee0
- Outcome
- Shikimic acid accumulation per mM of glyphosatee0
- Direction
- greatere0
- Comparator
- vegetative leaf tissuee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Shikimic acid accumulation per mM of glyphosate, wasgreater in reproductive than vegetative leaf tissue in both GR and conventional cotton”
Claim · model-written summary
CP4-EPSPS enzyme quantity was significantly lower in stamens than vegetative leaves.
- Taxon
- CottonGossypium hirsutumt0
- Organ / stage
- stamense0
- Gene
- CP4-EPSPSe0
- Outcome
- quantity of theglyphosate-resistant CP4-EPSPS enzymee0
- Direction
- lesse0
- Comparator
- vegetative leaf tissuese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The quantity of theglyphosate-resistant CP4-EPSPS enzyme was significantly less in stamens than in vegetative leaf tissues.”
t0“Cotton”
Claim · model-written summary
Glyphosate inhibited stamen elongation, leaving anthers short of the stigma tip.
- Taxon
- CottonGossypium hirsutumt0
- Treatment
- Glyphosate applicationse0
- Outcome
- stamen elongatione0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Glyphosate applications inhibited stamen elongation, resulting in anthers not extending to the tip of the stigma”
t0“Cotton”
Claim · model-written summary
Glyphosate-treated resistant cotton received less pollen on the stigma.
- Taxon
- cottonGossypium hirsutume0
- Treatment
- glyphosate-treatede0
- Outcome
- Total pollen deposition on the stigmae0
- Direction
- lesse0
- Comparator
- non-treated GR or conventional cottone0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Total pollen deposition on the stigma was less in glyphosate-treated GR cotton than non-treated GR or conventional cotton.”
Claim · model-written summary
Glyphosate arrested pollen maturation at at least three developmental stages.
- Taxon
- CottonGossypium hirsutumt0
- Treatment
- glyphosatee0
- Outcome
- maturatione0
- Direction
- arrestede0
- Value
- at least 3 pollen developmental stagese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“glyphosate arrested maturation in at least 3 pollen developmental stages.”
t0“Cotton”
Claim · model-written summary
Pollen from treated resistant cotton was collapsed and highly vacuolated at anthesis.
- Taxon
- CottonGossypium hirsutumt0
- Outcome
- pollen grainse0
- Qualifier
- collapsed, highly vacuolatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pollen grains from glyphosate-treated GR plants were collapsed, highly vacuolated”
t0“Cotton”
Claim · model-written summary
Treated resistant cotton pollen viability was 60% lower than untreated resistant or conventional cotton.
- Taxon
- CottonGossypium hirsutumt0
- Outcome
- viabilitye0
- Direction
- lowere0
- Value
- 60%e0
- Comparator
- non-treated GR or conventional plantse0
Not reportedTreatment
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“had 60% lowerviability (ability to germinate) than pollen from non-treated GR or conventional plants.”
t0“Cotton”
Claim · model-written summary
Retained bolls from glyphosate-treated plants had fewer seeds.
- Taxon
- CottonGossypium hirsutumt0
- Treatment
- glyphosate-treatede0
- Outcome
- seedse0
- Direction
- fewere0
- Comparator
- non-treated GR or conventional plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Retained bolls fromglyphosate-treated plants had fewer seeds than those from non-treated GR or conventional plants.”
t0“Cotton”
Claim · model-written summary
Treating the male parent reduced seeds per boll in hand crosses; female treatment did not.
- Taxon
- CottonGossypium hirsutumt0
- Treatment
- maleparente0
- Outcome
- number of seeds per bolle0
- Direction
- decreasede0
- Comparator
- female parente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the number of seeds per boll was decreased when the maleparent, but not the female parent, was glyphosate treated.”
t0“Cotton”
Claim · model-written summary
Hand pollination failed to restore normal seeds per boll, and GA failed to remediate pollen viability and floral morphology.
- Taxon
- CottonGossypium hirsutumt0
- Outcome
- normal number of seeds per bolle0
- Direction
- did not restoree0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Hand pollinations using pollen from treated plants,although overcoming the increased anther-stigma distance, did not restore the normal number of seeds per boll.Treatment of GA onto glyphosate-treated GR plants did not remediate glyphosate effects on pollen viability andfloral morphology.”
t0“Cotton”
The same questions in other papers
glyphosate · phenology · Gossypium hirsutum (cotton)Results differ
5 papers in the same direction as this paper
- negative
- no effect
- no effect
2 papers more in this group
See all 6 papers →glyphosate · growth · Gossypium hirsutum (cotton)Results differ
8 papers in the same direction as this paper · 4 in the opposite direction
- positive
- positive
- positive
9 papers more in this group
See all 13 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.