Tax implications for sending money from USA to India

If  Son  is  NRI   then  he can  open  NRE (saving )   Account  in the Indian  bank ,  one can  deposit   Income deemed  to  be earned  outside India  in this  Account ,However  you can not  deposit  Indian rupee in this account ,you only can deposit foreign  currency which will be converted in to Indian rupees . The Interest earned on the balance  at the end of  quarter  is free form Income Tax  ,   NRI can send his remittance form abroad  . 

For all above he must be NRI .For monitory limits  and current  Income Tax implication  you confirm from  bank 

Joint NRE saving  account  with  resident  Indian ( Mother)  is  not  permitted .

Son living in US has option to open NRE or NRO a/c.

The difference between NRE & NRO accounts is that while an NRE account is a bank account opened in India in the name of an NRI, to park his foreign earnings; whereas, an NRO account is a bank account opened in India in the name of an NRI, to manage the income earned by him in India. Son may open a NRE a/c in single name or with another NRI (whose interest income is exempt in India) & a NRE a/c jointly with his mother & transfer funds from NRE to NRO a/c. Interest on NRO a/c is taxable in hands of son in India (no tax for mother, for whom it is gift from son). An NRE account allows you to transfer funds to another NRE account as well as to an NRO account. You can transfer funds from an NRO to another NRO account, but you cannot transfer funds from an NRO account to an NRE account.