Abstract
The frequency of pollen mother cells with univalent chromosomes at first metaphase was determined in five varieties and ten varietal hybrids of vulgare wheats. The proportion of cells with univalents in the varieties varied from 2.9 per cent to 9.7 per cent and in the hybrids from 5.2 to 39.1 per cent. Hybrids between related varieties on the whole gave lower univalent frequencies than those between unrelated varieties, but exceptions occurred.In any cell with univalents two was the most common number, and as high as eight were observed. Trivalents and tetravalents were seen only rarely.Wide variation in percentage of cells with univalents was observed in some instances. Higher univalent frequency occurred in first metaphase cells from anthers in which most of the cells were well past metaphase.No significant difference in univalent frequency was found in two groups of Marquis plants kept under fairly constant temperatures the respective means of which were 60° and 77°F.The univalents in different cells were of different sizes and shapes. In certain hybrids with high univalent frequency, the univalents seemed to be longer than in certain varieties. Attenuated bivalents and bivalents with fewer chiasmata were more frequent in hybrids with frequent univalents.Typical metaphase bivalents are drawn and the number of chiasmata estimated for each. Terminal or terminal and closely sub-ter-minal chiasmata are the rule but exceptions occur. Configurations resembling some of those interpreted by HUSKINS and by POWERS as trivalents are here interpreted as bivalents.It is to be expected that the occurrence of univalents will give rise in the next generation to plants with abnormal chromosome numbers and to disturbed genetic ratios.The relationship of these observations to the chiasma theory is discussed and it is concluded that they support DARLINGTON's theory which ascribes the occurrence of univalents to a reduction in frequency of chiasmata.
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Claims 18
Claim · model-written summary
Univalent-bearing cells ranged from 2.9 to 9.7 per cent among varieties.
- Taxon
- Triticum vulgare
Triticum aestivumt0 - Material
- varietiese0
- Outcome
- proportion of cells with univalentse0
- Value
- 2.9 per cent to 9.7 per cente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The proportion of cells with univalents in the varieties varied from 2.9 per cent to 9.7 per cent”
t0“Triticum vulgare”
Claim · model-written summary
Univalent-bearing cells ranged from 5.2 to 39.1 per cent among hybrids.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Material
- hybridse0
- Outcome
- cells with univalentse1
- Value
- 5.2 to 39.1 per cente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the hybrids from 5.2 to 39.1 per cent”
t0“Triticum vulgare”
e1“The proportion of cells with univalents in the varieties varied from 2.9 per cent to 9.7 per cent”
Claim · model-written summary
Related-variety hybrids generally had lower univalent frequencies than unrelated-variety hybrids, with exceptions.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Material
- Hybrids between related varietiese0
- Outcome
- univalent frequenciese0
- Direction
- lowere0
- Qualifier
- but exceptions occurrede0
- Comparator
- those between unrelated varietiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Hybrids between related varieties on the whole gave lower univalent frequencies than those between unrelated varieties, but exceptions occurred.”
t0“Triticum vulgare”
Claim · model-written summary
Two was the most common number of univalents per cell.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Outcome
- numbere0
- Value
- twoe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In any cell with univalents two was the most common number, and as high as eight were observed.”
t0“Triticum vulgare”
Claim · model-written summary
Up to eight univalents were observed in a cell.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Outcome
- univalentse0
- Value
- eighte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In any cell with univalents two was the most common number, and as high as eight were observed.”
t0“Triticum vulgare”
Claim · model-written summary
Trivalents and tetravalents were rare.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Outcome
- Trivalents and tetravalents were seen only rarelye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Trivalents and tetravalents were seen only rarely.”
t0“Triticum vulgare”
Claim · model-written summary
Some samples showed wide variation in the percentage of cells with univalents.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Outcome
- percentage of cells with univalentse0
- Qualifier
- in some instancese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Wide variation in percentage of cells with univalents was observed in some instances.”
t0“Triticum vulgare”
Claim · model-written summary
Anthers with cells mostly past metaphase had higher univalent frequency in first-metaphase cells.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Organ / stage
- antherse0
- Outcome
- univalent frequencye0
- Direction
- Highere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Higher univalent frequency occurred in first metaphase cells from anthers in which most of the cells were well past metaphase.”
t0“Triticum vulgare”
Claim · model-written summary
Marquis plants at mean temperatures of 60° and 77°F did not differ significantly in univalent frequency.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Material
- Marquise0
- Treatment
- 60°e0
- Outcome
- univalent frequencye0
- Direction
- No significant differencee0
- Comparator
- 77°Fe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“No significant difference in univalent frequency was found in two groups of Marquis plants kept under fairly constant temperatures the respective means of which were 60° and 77°F.”
t0“Triticum vulgare”
Claim · model-written summary
Univalents varied in size and shape across cells.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Outcome
- different sizes and shapese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The univalents in different cells were of different sizes and shapes.”
t0“Triticum vulgare”
Claim · model-written summary
In some high-univalent-frequency hybrids, univalents seemed longer than in some varieties.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Material
- certain hybridse0
- Outcome
- univalentse0
- Direction
- longere0
- Qualifier
- seemed to bee0
- Comparator
- certain varietiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In certain hybrids with high univalent frequency, the univalents seemed to be longer than in certain varieties.”
t0“Triticum vulgare”
Claim · model-written summary
Attenuated bivalents were more frequent in hybrids with frequent univalents.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Material
- hybrids with frequent univalentse0
- Outcome
- Attenuated bivalentse0
- Direction
- more frequente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Attenuated bivalents and bivalents with fewer chiasmata were more frequent in hybrids with frequent univalents.”
t0“Triticum vulgare”
Claim · model-written summary
Bivalents with fewer chiasmata were more frequent in hybrids with frequent univalents.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Material
- hybrids with frequent univalentse0
- Outcome
- bivalents with fewer chiasmatae0
- Direction
- more frequente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Attenuated bivalents and bivalents with fewer chiasmata were more frequent in hybrids with frequent univalents.”
t0“Triticum vulgare”
Claim · model-written summary
Terminal or closely subterminal chiasmata were usual, with exceptions.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Outcome
- Terminal or terminal and closely sub-ter-minal chiasmatae0
- Qualifier
- but exceptions occure0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Terminal or terminal and closely sub-ter-minal chiasmata are the rule but exceptions occur.”
t0“Triticum vulgare”
Claim · model-written summary
Some configurations previously interpreted as trivalents are interpreted here as bivalents.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Outcome
- interpreted as bivalentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Configurations resembling some of those interpreted by HUSKINS and by POWERS as trivalents are here interpreted as bivalents.”
t0“Triticum vulgare”
Claim · model-written summary
The authors expect univalents to produce abnormal chromosome numbers in the next generation.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Outcome
- plants with abnormal chromosome numberse0
- Qualifier
- occurrence of univalentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“It is to be expected that the occurrence of univalents will give rise in the next generation to plants with abnormal chromosome numbers and to disturbed genetic ratios.”
t0“Triticum vulgare”
Claim · model-written summary
The authors expect univalents to disturb genetic ratios in the next generation.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Outcome
- disturbed genetic ratiose0
- Qualifier
- occurrence of univalentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“It is to be expected that the occurrence of univalents will give rise in the next generation to plants with abnormal chromosome numbers and to disturbed genetic ratios.”
t0“Triticum vulgare”
Claim · model-written summary
The observations support a theory that reduced chiasma frequency causes univalents.
- Taxon
- Triticum vulgareTriticum aestivumt0
- Outcome
- occurrence of univalentse0
- Qualifier
- reduction in frequency of chiasmatae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“they support DARLINGTON's theory which ascribes the occurrence of univalents to a reduction in frequency of chiasmata.”
t0“Triticum vulgare”