Types and meaning of pollen carbohydrate reserves

During pollen development, soluble carbohydrates of sporophytic origin may be consumed immediately, polymerized to form starch reserves or intine, or transformed into other molecules. Disregarding intine, in mature pollen there are three different types of carbohydrates: (1) polysaccharides such as starch in amyloplasts or polysaccharides in cytoplasmic vesicles, (2) disaccharides such as sucrose and (3) monosaccharides such as glucose and fructose. At dispersal, pollen may be partly or slightly dehydrated, or not dehydrated at all. Partly dehydrated pollen has the capacity to lose or acquire water within limits without detriment to its viability. Slightly and non-dehydrated pollen is vulnerable to water loss and quickly becomes inviable. In partly dehydrated of pollen the carbohydrates consist of cytoplasmic polysacharides and sucrose; in slightly and non-dehydrated pollen these are absent or in low concentrations but there may be reserves of cytoplasmic callose. Starch, glucose and fructose are found in both types. It is postulated that cytoplasmic carbohydrates and sucrose are involved in protecting pollen viability during exposure and dispersal.