Abstract
The effects of pollination on both embryo sac development and gibberellin (GA) content in walnut ( Juglans regia L.) ovaries were investigated. Microscopic observations on early structural changes in the embryo sac indicated that fertilization occurred shortly after pollination (within 5 days). In unpollinated ovaries, the two polar nuclei also fused during this period, leading to a 2n endosperm which started cellularization (wall formation) about 5 days later. Zygote division in pollinated ovaries started approximately 9 days after fertilization while the endosperm at this stage was still in the free‐nuclear phase. Gas chromatography‐mass spectrometry (GC‐MS) analyses of GAs in pollinated and unpollinated ovaries demonstrated the presence of all members of the 13‐hydroxylation GA pathway (GA 53 , GA 44 , GA 17 , GA 19 , GA 20 , GA 29 , GA 1 , and GA 8 ). In addition, GA 4 , GA 9 , and an unknown monohydroxy‐GA 12 were also detected. Endogenous GAs were quantified by selected ion monitoring (SIM) from pollination up to 13 days later. At the end of this period, pollinated ovaries contained high levels of C 20 GAs whereas C 19 GAs had declined. Gibberellins A 44 and A 19 increased slightly shortly after fertilization, then decreased, and lastly accumulated. Gibberellin A 20 followed the same step‐by‐step trend albeit in an opposite manner. Gibberellin A 1 showed a transitory increase immediately after fertilization and decreased gradually subsequently. The pattern of GA change in unpollinated ovaries differed mostly as follows: (1) within 13 days after the time of pollination GA 53 and GA 44 decreased; (2) GA 19 increased continuously; (3) GA 20 decreased also continuously following the opposite pattern to GA 19 ; and (4) the brief rise in GA 1 was higher (2‐fold) than in pollinated ovaries, although 13 days after the time of pollination its levels were much lower in unpollinated ones. These results suggest that the sequence pollination/fertilization modulates GA 1 levels, first reducing them immediately after fertilization, and subsequently, stimulating moderate amounts shortly thereafter at the beginning of embryogenesis. In unpollinated ovaries the lowest GA I levels coincided with ovary growth arrest, the onset of a rapid and heavy abscission (100%), and an accelerated 2n endosperm cellularization. However, repeated exogenous GA 3 applications did not suppress the growth arrest and abscission.
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Claims 17
Claim · model-written summary
Fertilization occurred within five days after pollination.
Verbatim
e0“fertilization occurred shortly after pollination (within 5 days)”
t0“walnut (Juglans regia)”
Claim · model-written summary
Polar nuclei fused in unpollinated ovaries and produced cellularizing 2n endosperm about five days later.
Verbatim
e0“In unpollinated ovaries, the two polar nuclei also fused during this period, leading to a 2n endosperm which started cellularization (wall formation) about 5 days later.”
t0“walnut (Juglans regia)”
Claim · model-written summary
Zygote division in pollinated ovaries began about nine days after fertilization while endosperm remained free nuclear.
Verbatim
e0“Zygote division in pollinated ovaries started approximately 9 days after fertilization while the endosperm at this stage was still in the free‐nuclear phase.”
t0“walnut (Juglans regia)”
Claim · model-written summary
Pollinated and unpollinated ovaries contained all listed members of the 13-hydroxylation GA pathway.
Verbatim
e0“Gas chromatography‐mass spectrometry (GC‐MS) analyses of GAs in pollinated and unpollinated ovaries demonstrated the presence of all members of the 13‐hydroxylation GA pathway (GA 53 , GA 44 , GA 17 , GA 19 , GA 20 , GA 29 , GA 1 , and GA 8 ).”
t0“walnut (Juglans regia)”
Claim · model-written summary
GA 4, GA 9 and an unknown monohydroxy GA 12 were also detected.
Verbatim
e0“In addition, GA 4 , GA 9 , and an unknown monohydroxy‐GA 12 were also detected.”
t0“walnut (Juglans regia)”
Claim · model-written summary
At day 13 pollinated ovaries had high C 20 GA levels.
Verbatim
e0“At the end of this period, pollinated ovaries contained high levels of C 20 GAs whereas C 19 GAs had declined.”
t0“walnut (Juglans regia)”
Claim · model-written summary
At day 13 C 19 GAs had declined in pollinated ovaries.
Verbatim
e0“At the end of this period, pollinated ovaries contained high levels of C 20 GAs whereas C 19 GAs had declined.”
t0“walnut (Juglans regia)”
Claim · model-written summary
GA 44 and GA 19 rose slightly after fertilization, then fell and accumulated.
Verbatim
e0“Gibberellins A 44 and A 19 increased slightly shortly after fertilization, then decreased, and lastly accumulated.”
t0“walnut (Juglans regia)”
Claim · model-written summary
GA 20 followed the opposite stepwise pattern.
Not reportedDirection
Verbatim
e0“Gibberellin A 20 followed the same step‐by‐step trend albeit in an opposite manner.”
t0“walnut (Juglans regia)”
Claim · model-written summary
GA 1 rose transiently immediately after fertilization and then gradually declined.
Verbatim
e0“Gibberellin A 1 showed a transitory increase immediately after fertilization and decreased gradually subsequently.”
t0“walnut (Juglans regia)”
Claim · model-written summary
In unpollinated ovaries, GA 53 and GA 44 declined over 13 days.
Verbatim
e0“within 13 days after the time of pollination GA 53 and GA 44 decreased”
e1“The pattern of GA change in unpollinated ovaries”
t0“walnut (Juglans regia)”
Claim · model-written summary
In unpollinated ovaries, GA 19 rose continuously.
Verbatim
e0“GA 19 increased continuously”
t0“walnut (Juglans regia)”
Claim · model-written summary
In unpollinated ovaries, GA 20 fell continuously.
Verbatim
e0“GA 20 decreased also continuously following the opposite pattern to GA 19”
t0“walnut (Juglans regia)”
Claim · model-written summary
The transient GA 1 rise was twice as high in unpollinated as pollinated ovaries, but lower at day 13.
Verbatim
e0“the brief rise in GA 1 was higher (2‐fold) than in pollinated ovaries, although 13 days after the time of pollination its levels were much lower in unpollinated ones.”
t0“walnut (Juglans regia)”
Claim · model-written summary
The authors infer pollination and fertilization modulate GA 1 levels during embryogenesis.
Verbatim
e0“These results suggest that the sequence pollination/fertilization modulates GA 1 levels, first reducing them immediately after fertilization, and subsequently, stimulating moderate amounts shortly thereafter at the beginning of embryogenesis.”
t0“walnut (Juglans regia)”
Claim · model-written summary
In unpollinated ovaries the lowest GA I levels coincided with growth arrest, complete abscission and accelerated 2n endosperm cellularization.
- Taxon
- walnutt0
- Organ / stage
- unpollinated ovariese0
- Compound
- GA Ie0
- Outcome
- ovary growth arrest, the onset of a rapid and heavy abscission (100%), and an accelerated 2n endosperm cellularizatione0
Not reportedDirection
Verbatim
e0“In unpollinated ovaries the lowest GA I levels coincided with ovary growth arrest, the onset of a rapid and heavy abscission (100%), and an accelerated 2n endosperm cellularization.”
t0“walnut (Juglans regia)”
Claim · model-written summary
Repeated GA 3 application failed to suppress growth arrest and abscission.
- Taxon
- walnutt0
- Treatment
- repeated exogenous GA 3 applicationse0
- Outcome
- growth arrest and abscissione0
- Direction
- did not suppresse0
Not reportedComparator
Verbatim
e0“However, repeated exogenous GA 3 applications did not suppress the growth arrest and abscission.”
t0“walnut (Juglans regia)”
The same questions in other papers
Gibberellic acid · yield · Juglans (walnuts)Positive and negative results
3 in the opposite direction
- positive
- positive
- positive
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.