The roots of the aquatic plant hydrilla are poorly developed and lack xylem tissue. Which is an appropriate justification for this?

Hydrilla is a hydrophyte, who have a characteristic of poorly developed root system because they are already surrounded by plenty of water and can absorb water anytime, from their surface. Further, this is why they lack a xylem tissue also. Xylem is required for water transport, which is a very easy task for hydrophytes, as they absorb water from their surface.