Claim · model-written summary
One or two nucleoli are usually present and remain normal in appearance after the spindle is far advanced.
- Taxon
- Agave virginica
Agave virginicat0 - Outcome
- One or two nucleolie0
Not reportedMaterialGeneCompoundOrgan / stageInteractorInteractor roleSecond interactorSecond interactor roleTreatmentComparatorSettingDirectionValueQualifier
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Agave virginica”
e0“One or two nucleoli are usually present, which are still normal in appearance after the spindle is far advanced in development”
Title
The Reduction Division in the Microsporocytes of Agave virginica
John H. Schaffner Botanical Gazette 1909. doi:10.1086/329850
Other claims from this paper (19)
- Observation The resting nucleus of the microsporocytes contains a linin network holding small chromatin granules, either separate or in lumps.
- Observation At the beginning of division the chromatin granules mass into lumps corresponding approximately to the reduced chromosome number.
- Observation The authors interpret the chromatin masses as probably representing bivalent protochromosomes.
- Observation The masses unite and elongate into a delicate continuous spirem holding a single row of chromatin granules.
- Observation After the delicate spirem stage, nuclei in killed material are usually in synizesis.
- Observation Two spirems do not unite in synizesis.
- Observation In living material no synizesis is evident and the nucleoli are not crowded against the nuclear wall but usually lie centrally in the nuclear cavity.
- Observation The authors conclude that synizesis at this and later stages is an artifact.
- Observation The spirem shortens and thickens while the chromatin granules undergo transverse division.
- Observation The spirem orients itself into twelve loops of different shapes and sizes.
- Observation The loops press against the nuclear membrane in a wreathlike circle and do not radiate from a central mass as in Lilium.
- Observation The twelve loops break apart into twelve chromosomes: four very large twisted, three ring-shaped and five smaller irregular bean-shaped chromosomes.
- Observation Connecting fibers unite the chromosomes and apparently draw the scattered chromosomes into the equatorial plane while the spindle elongates.
- Observation The spindle originates as a fibrous layer over the surface of the nuclear membrane before the membrane dissolves.
- Observation The spindle is bipolar from the first, with no accessory smaller poles.
- Observation Spindle fibers are usually thickest in the middle even in early stages, and definite asters are commonly present at the poles.
- Observation The authors explain the observed multipolar spindles as artifacts mostly produced by cutting.
- Observation The chromosomes divide transversely during metakinesis.
- Observation In the second division the chromosomes divide longitudinally.