Plants tend to accumulate fats only when it is important to pack a lot of energy into a small space, such as a seed. Membrane lipids are similar to triglycerides except that one of the fatty acids is replaced by a polar group such as a sugar in a glycolipid or a phosphate compound in a phospholipid. Cuticular lipids are a complex mix of hydrocarbons and esters of long chain aliphatic acids and alcohols embedded in a lipid polymer called cutin. Waxes and cutin make up the cuticle which is a water-retaining barrier around the above ground parts of plants. All carbohydrates are polar and the low-molecular forms are what we commonly know as sugars.
Sugars are freely soluble in water.
The simplest is the three carbon sugar, glyceraldehyde but most of the carbohydrates in plants are based on glucose or other six carbon sugars. Like other sugars glucose can exist in two basic forms, an open chain or a ring structure. This then influences how the sugars can be joined together in larger molecules. When sugars move around the plant they are usually in the form of sucrose in which glucose and fructose are joined by a glycosidic bond. This bond is made by removing the elements of water from two sugars.