Why we can only observe chromosome loss - not increase in chromosome numbers?

[pevaquark (Matthew Pevarnik)]

@Bill_II

But by having two copies the plant can do something that the plant with one copy can not. While it might not be an increase in information in a strict sense it is an increase in function.

As you said, the duplication in itself wouldn’t add much but it provides a lot of new material to play around with at no detriment to the organism. Here’s a nice example from drosophila where duplication events led to novel expressions through exon shuffling (@aarceng) :

Tandem duplications lead to novel expression patterns through exon shuffling...