OCCURRENCE OF MONOSACCHARIDE OR DISACCHARIDE AND POLYSACCHARIDE RESERVES IN MATURE POLLEN GRAINS

Pollen from 13 species of gymnosperms and angiosperms was studied for soluble and insoluble carbohydrates at dispersal. Starch reserves stor ed during pollen development give rise to carbohydrates at maturity. C ombinations of different types of carbohydrates in mature pollen may d epend on the extent of starch hydrolysis. An inverse relationship was found between the extent of starch hydrolysis and sucrose content. If the starch was scarcely de-polymerized, the cytoplasm had very low lev els of soluble sugars and none of the periodic acid-Schiff (PAS)-posit ive material as found in pollen not subject to high dehydration (Cucur bita pepo L., Zea mays L.). After total or partial starch hydrolysis, insoluble PAS-positive oligo/polysaccharides were found in the cytopla sm associated with much soluble sugar, and the pollen grains were dehy drated at dispersal as in Typha latifolia L., Chamaerops humilis L., T rachycarpus excelsa Wendl.. and other specimens. Intermediate levels o f starch and soluble sugars, together with cytoplasmic PAS-positive ma terial, characterized species with dehydrated pollen such as Pinus hal epensis Miller. Carbohydrates may be related to pollen longevity, whic h largely depends on the abundance of sucrose, which is known to prote ct membrane integrity. The relationship between PAS-positive material and pollen viability is unclear at present.