Claim · model-written summary
The masses unite and elongate into a delicate continuous spirem holding a single row of chromatin granules.
- Taxon
- Agave virginica
Agave virginicat0 - Outcome
- delicate, continuous spireme0
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“The masses are all united and elongate greatly until a very delicate, continuous spirem is produced, holding a single row of chromatin granules”
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 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 One or two nucleoli are usually present and remain normal in appearance after the spindle is far advanced.
- 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.