Pachytene Stage of Meiosis in Plants
Pachytene stage starts just when the synapsis has finished. The paired chromosome formations are called bivalents. If there are more than two homologues in paired situation, they are called “multivalents”, e.g., trivalents, quadrivalents, pentavalents etc.
The following changes are seen in this sub-phase;
- As a result of continuous coiling, the chromosomes are seen more short and thick.
- Each chromosome is seen divided vertically except the centromere, so each bivalent has four chromatids which are called tetrad.
- The two chromatids of the same chromosomes is known as sister chromatids the chromatids of different chromosomes are called non-sister chromatids.
- Chromosomes are visible along the length of bivalents; their pattern can be used to identify specific bivalents or their segments.
- Nucleoli are observable during pachytene; in many species they are united to form one large nucleolus
Pachytene Stage of Meiosis is most essential for the completion of life cycle of a plant as it brings a change from diploid to haploid generation.