Long term capital gains on property gifted by son to mother

If a Son transfers a plot to his mother through a registered gift/transfer deed after paying the stamp duty as applicable, what happens if the mother sells it  :

After 1 Year and

After 2 years

(The period of holding of the Son shall be counted for calculating LTCG of the mother- this is quite clear)

But in whose hands the LTCG be taxable?

I have read Sec 64 and did not find this situation in it but then I am not an expert.

I look forward to your expert advice in the matter.