Can I join ISRO after B.Sc. Botany?

Yes, you may join Indian Space Research organisation (ISRO) at the level of Scientific Assistant but not as a scientist also, you can join as a technician or assistant engineer. It's on the lower end of the hierarchy. However, Indian Space Research organisation allows you the option of part-time or

No but Yes you can join ISRO and after M.Sc. In botany. But the salary will not be that pleasant as compared to the engineers of ISRO and BARC and their other officials. You will get to work in a somewhat lower post.