You haven't mentioned the Entrance examination you are enquiring about. There are State level Entrance examinations like HORTICET for Andhra Pradesh. Please do help us with the Entrance examination you are enquiring about and we shall help you with relevant information. Until then, you can refer few books on Horticulture like:

Handbook of Horticulture by Chadha K L

Basic Horticulture by Jitendra Singh

Horticulture at a Glance by D Ram and B B Singh

MCQs in Horticulture by Bharat Singh Hada

Objective Horticulture by Anil Verma

Question Bank of Horticulture by Gupta S.N

Glaustas Horticulture by P Muthukumar