Option 1: Hydrilla is not a vessel-less angiosperm. It is an aquatic plant that belongs to the family Hydrocharitaceae. It has specialized tissue called xylem vessels that transport water and nutrients throughout the plant.

Option 2: Trochodendron is the correct answer. It is a genus of angiosperms that is vessel-less. This means that it lacks the specialized xylem vessels found in most angiosperms, which are responsible for conducting water and nutrients.

Option 3: Maize is not a vessel-less angiosperm. It belongs to the family Poaceae, and like other grasses, it possesses xylem vessels in its vascular tissue.

Option 4: Wheat is not a vessel-less angiosperm either. It belongs to the family Poaceae and has xylem vessels.

Therefore, the correct answer given is option 2, Trochodendron, as it is the only vessel-less angiosperm among the options provided.