Green algae lack the vascular tissues, that is they do not have phloem or xylem for transporting water and nutrients throughout their bodies. They have a thalloid that means they do not have a body divided into root stem and leaves. The thalloid body helps in absorbing nutrients from surroundings.
The land-based plants have xylem and phloem (vascular tissues) to transport water, nutrients, and minerals throughout the body.
Lipids would be the answer that you are looking for. When talking food energy it's best to speak in terms of calories. Therefore, lipids or fats offer the greatest amount of heat or energy.
