Question

In hydrophytes xylem is less developed why?

Answer 1

most hydrophytes have little or no xylem as the majority of the plant has access to water. This means water can diffuse into different parts of the plants and therefore doesn't need to be transported around it. The absence of a well-developed xylem and consequently lignin, means that most stems of hydrophytes have little rigidity. Hydrophytes don't have adaptations for protecting their water supplies as they are surrounded by it. Therefore they have unlimited access to the resource and can easy get more if need be. 

Answer 2

Xylem is less developed  because they do not require well developed water conducting system.