What is the difference between the structure of xylem in a floating water plant and a land plant?

To be specific, the water plant is water lily.

Is it that the xylem in the water plant has to have more lignin deposits to keep the plant upright?

What is the difference between the structure of xylem in a floating water plant and a land plant?
Not sure if there's a differences in both of the plants. But i'm sure that floating water plant have some air sacs in their stem and leaf structure and it called aerenchyme (maybe i miss spell it ^___^). This specialized tissue is designed to keep the stem and the leaves floating.