With a score of 220 marks, an overall rank of 1277, and a category rank of 538 in the OBC NCL category, your chances of securing a good college in Plant Science can vary based on several factors:

1. **College Cut-offs**:

- **Research Cut-offs**: Review the previous years' cut-off marks for Plant Science in various colleges. This information is usually available on college websites or through educational portals. Compare your rank with these cut-offs to gauge your chances.

2. **Category and Reservation**:

- **OBC NCL Reservation**: Your OBC NCL category rank can improve your chances as many institutions have reserved seats for this category. Check the specific reservation policies of the colleges you are interested in.

3. **Top Colleges**:

- **Reputable Institutions**: Consider top institutions that offer Plant Science programs. Colleges like Delhi University, Banaras Hindu University, and Jawaharlal Nehru University may have varying cut-offs. Research these institutions to see if your rank falls within their acceptable range.

4. **Counseling and Seat Allocation**:

- **Participate in Counseling**: Engage actively in the counseling process. Sometimes, lower-ranked candidates may secure admission due to factors like seat availability or changes in cut-offs.

5. **Backup Options**:

- **Explore Alternatives**: If your preferred colleges are highly competitive, also consider applying to other institutions with potentially lower cut-offs or explore related fields in science.

Ultimately, your chances depend on the specific cut-offs of the colleges you are targeting and the availability of seats in your category.