if any plant cell has n=16 then what will happen in the meiosis metaphase-1?

The homologous chromosomes will align on the metaphase plate & the spindle fibres will get attached with the kinetochores of homologous chromosomes resulting their separation i.e. 8 will go one side & another 8 on other side.

Number of chromosome at metaphase, in meioisis 1 will be equal to its 2n (Dipoild) number i.e. 32