Under Indian employment laws, is an employer bound to pay wages on public holidays falling during a strike?

This is a difficult question to answer, as each State Government has separate laws as to paid holidays. For E.g. in Karnataka, there is an Industrial Act, Karnataka Industrial Establishments (National and Festival Holidays) Act, 1963 which provides for mandatory paid holidays by the establishments in Karnataka.
As per Indian employment law, the issue of whether the employer is bound to pay wages for paid holidays during the period of strike depends upon various factors such as whether strike is legal or justified.

The Hon’ble Supreme Court, in the matter of Madura Coats Limited V/s Inspector of Factories, First Circle, Madurai and Anr. (Civil Appeal No. 34 of 1980, decided on 02.12.1980) held that
“It would depend on the facts and circumstances of each case whether or not wages become payable in the context of strike. It is true that where a strike is neither illegal being not in contravention of any statutory provision, nor unjustified having been lodged as a protest against the unreasonable attitude of the management, there is no reason to deprive the workmen of their wages. It must, nevertheless, be observed that workmen cannot resort to strike with impunity for any kind of demand without first exhausting reasonable avenues for possible achievement of their object.”

Payment of wages for national holidays falling within the period of strike depends upon the terms of settlement as well as legality and justification of strike. Therefore there cannot be a standard answer to this question. Each case will have to be examined in the context.