Hi Priyanka,
Firstly I would advise you to prepare a really good time table. open the universities official website and check for previous years question paper and start going through them. Also I would advise you to download the the previous years bachelors syllabus for botany and go through them. most of the questions asked will be related to to what was thought in bachelors from that University. In my opinion solving question papers from the previous years is a best option. for books advise you to go through your bachelors degrees reference books and college books that will be enough. All in all don't take stress and answer in peace.
All the best and good luck