Hi,

it's very good that you want to become a botanist for that you have to attend a entrance exam according to the university .eligibility for  botanist is that individual must score minimum 50% on average or above for the 10+2.But  most of the universities admissions are taken through merit .for more details of the admissions and  course syllabus details please check the below link mention below

https://www.careers360.com/courses/botany-course

All the best!