I would definitely know the vascular system, structure, parts of a flower, taxonomy, gymnosperms, angiosperms, monocots, dicots, plant hormones photosynthesis. Basically the plant stuff covered in the gen biology class.
I would say know a little about a lot of the plants. Hope this makes sense. You don't wanna shoot yourself in the foot. If you don't have time, just do the practice test at the back of cliffs ap bio and you should be fine. hopefully...😕