Types of carbohydrate reserves in pollen: localization, sistematic distribution and ecological significance

Dehiscing pollen grains of 901 species belonging to 104 dicot families and 15 monocot families were scored for starch reserves. Starch grains showed different physico-chemical properties i.e. colour after iodine - potassium iodide staining and birefringence or otherwise under polarized light. Further tests performed in a limited number of species revealed other kinds of carbohydrate reserves in the cytoplasm but outside plastids. From these observations, it results that carbohydrate reserves may be stored in plastids only (amyloplasts), in the cytoplasm but not in plastids, or in both. These kinds of pollen reserves are only partly in line with systematics, as only certain families consistently show the same type of reserve. These and previous findings suggest that the presence of polysaccharides in the cytoplasm prevents rapid decrease in viability due to desiccation. In this sense, our findings are in line with ecophysiological adaptations such as the respective pollination syndrome.