Why do Ophioglossum plants (commonly known as Adder's tongue) have up to 1,400 chromosomes?

Question

Why do Ophioglossum plants (commonly known as Adder's tongue) have up to 1,400 chromosomes?

Answer 1

I had to look this up myself, and there seems to be some disagreement on whether all these chromosomes are truely different, or if they are multiples of sets.

I have founds sources that say that the large number (I've seen it most often quotes as 1260 chromosomes) are diploid, making it 630 pairs of chromosomes, but other sources say the number is because of polyploidy - where there are more than two of each.  What might have happened is that at some point an ancestor of today's plants had chromosomes that didn't separate correctly during meiosis, and one daughter cell ended up with an extra set of chromosomes.  That would be like in a human that is supposed to have 2 sets of 23 chromosomes (or 46 total) having 69 chromosomes (one extra set in a cell) or 92 chromosomes (two extra sets) instead.  In animals, this condition is usually fatal, but not so for plants.  And this can happen more than once, which would also explain why there's some differences in the total number of chromosomes given.  And given enough time (hunderds of thousands of years), mutation may make some of the chomosomes different enough that they might not resemble each other anymore, only the opposite of their pair, so it may seem more like just two sets of each.