Abstract
ABSTRACT DNA endoreduplication in Zea mays L. (cv. A619 × W64A) endosperm peaks between 16 and 18 d after pollination (DAP). The physiological function of DNA endoreduplication is not known but it is believed to be important in maize kernel development. In the present study, we investigated how 2, 4 or 6 d of high temperature (35 °C) affected DNA endoreduplication and maize kernel development in comparison with control kernels grown at 25 °C. Data were collected on fresh weight (FW), nuclei number, mitotic index, and DNA endoreduplication. Maize endosperm FW and nuclei number were reduced by exposure to 4 or 6 d of high temperature. At 18 DAP, the 2 d high temperature treatment (HTT) caused a reduction in FW and nuclei number, but had no effect on DNA endoreduplication and average DNA content per endosperm. However, when the exposure to high temperature was increased to 4 or 6 d, FW, nuclei number and the magnitude of DNA endoreduplication were progressively reduced, and the peak mitotic index was delayed compared with the control endosperm. At 18 DAP, the 4 d treatment showed 54·7% of the cells were 3 or 6 C , whereas only 41·2% were 12 C or higher. Six days of high temperature also resulted in a reduction in endosperm FW, nuclei number and a delay in the peak of mitotic index. DNA endoreduplication occurred in the kernels exposed to this treatment, although the magnitude was severely reduced compared with the control kernels. Nuclear DNA content was highly correlated ( r = 0·93) with kernel FW, suggesting an important role of DNA endoreduplication in determining endosperm FW. The data suggest that high temperature during endosperm cell division exerted negative effects on DNA endoreduplication by dramatically reducing the nuclei number, leaving fewer nuclei available for DNA endoreduplication. However, the data also suggest that prolonged exposure to high temperature restricts entry of mitotic cells into the endoreduplication phase of the cell cycle.
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Claims 10
Claim · model-written summary
Maize endosperm endoreduplication peaks 16 to 18 days after pollination.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“DNA endoreduplication in Zea mays L. (cv. A619 × W64A) endosperm peaks between 16 and 18 d after pollination (DAP)”
Claim · model-written summary
Four or six days of high temperature reduced maize endosperm fresh weight and nuclei number.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Maize endosperm FW and nuclei number were reduced by exposure to 4 or 6 d of high temperature”
Claim · model-written summary
Two days of heat reduced fresh weight and nuclei number at 18 days after pollination.
Not reportedTaxonComparator
Verbatim
e0“At 18 DAP, the 2 d high temperature treatment (HTT) caused a reduction in FW and nuclei number”
Claim · model-written summary
Two days of heat had no effect on endoreduplication or average DNA content.
Not reportedTaxonTreatmentComparator
Verbatim
e0“but had no effect on DNA endoreduplication and average DNA content per endosperm”
Claim · model-written summary
Four or six days of heat progressively reduced fresh weight, nuclei number and endoreduplication.
- Treatment
- high temperaturee0
- Outcome
- FW, nuclei number and the magnitude of DNA endoreduplicatione0
- Direction
- progressively reducede0
Not reportedTaxonComparator
Verbatim
e0“when the exposure to high temperature was increased to 4 or 6 d, FW, nuclei number and the magnitude of DNA endoreduplication were progressively reduced”
Claim · model-written summary
Four or six days of heat delayed the peak mitotic index.
Not reportedTaxonTreatment
Verbatim
e0“the peak mitotic index was delayed compared with the control endosperm”
Claim · model-written summary
After four days of heat, 54.7% of endosperm cells were 3 or 6 C.
Not reportedTaxon
Verbatim
e0“the 4 d treatment showed 54·7% of the cells were 3 or 6 C”
Claim · model-written summary
After four days of heat, only 41.2% of cells were 12 C or higher.
Not reportedTaxon
Verbatim
e0“only 41·2% were 12 C or higher”
Claim · model-written summary
Nuclear DNA content strongly correlated with kernel fresh weight.
Not reportedTaxonDirection
Verbatim
e0“Nuclear DNA content was highly correlated ( r = 0·93) with kernel FW”
Claim · model-written summary
Prolonged high temperature was interpreted to restrict mitotic cell entry into endoreduplication.
- Treatment
- prolonged exposure to high temperaturee0
- Outcome
- entry of mitotic cells into the endoreduplication phase of the cell cyclee0
Not reportedTaxon
Verbatim
e0“prolonged exposure to high temperature restricts entry of mitotic cells into the endoreduplication phase of the cell cycle”
The same questions in other papers
heat · growth · Zea mays (maize)Results differ
49 papers in the same direction as this paper · 11 in the opposite direction
- negative
- negative
- negative
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See all 61 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.