Hello kritika,

Hope you're doing well.

For cracking BHU PET for botany , you  need to do the following:-

1. Study intermediate botany thoroughly.

2. Go through the notes and books given and prescribed by BHU professors for your discipline.

3. Solve last years question papers ( last 5-10 years).

4. Focus on systematic and classical botany.

For chemistry,

1. You need to have a good knowledge of chemistry which you studied in graduation

2. General sciences.

3. Last years question papers

Practice as much as you can. It'll always fetch you something:)

All the best.