Diplotene Stage of Meiosis in Plants:
After pachytene, the matching homologues start to shift separately; this stage is called diplotene. Synaptinemal multipart dissolves but the two homologous chromosomes in each bivalent remain joined by one or more chiasmata which symbolize the sites where crossing over has taken place
The changes of this sub-phase are as follows;
(i) Repulsion starts between the chromosomes of the bivalents. As result of which chromosomes starts moving away from each other.
(ii) But the chromosomes remain attached with the help of ‘X’ like chiasma produced in one or several places between non-sister chromatids.
(iii) At first the places of chiasma are broken down and the broken parts of chromatids are reunited inversely /differently between one with other.
(iv) Such type of exchange between homologous chromosomes is called crossing-over.
(v) The movement of chiasma towards the pole due to increasing of repulsion between the two homologous chromosomes is known as terminalization.
Due to the forces that repel the homologous chromosomes, the chiasmata slowly shift towards the telomeres and decline in number; this process is called chiasmaterminalization. Therefore, at later stages of diplotene, the actual position and number of crossovers cannot be determined.
