ULTRASTRUCTURE AND GERMINATION PERCENTAGE OF CROCUS-BIFLORUS MILLER SUBSP BIFLORUS (IRIDACEAE) POLLEN

Pollen of Crocus biflorus Miller subsp. biflorus from natural habitats of Tusculum (Frascati, near Rome, Italy) has been studied in order to compare its structure and physiology to pollen of other Crocus specie s belonging to the Crocus sativus group. Mature pollen grains are roun ded, 60 mum in diameter, inaperturate (but with surface incisions wher e exine is lacking). DAPI staining reveals a spindle-shaped generative nucleus which is intensely fluorescent, and vegetative nucleus which is less fluorescent, and is elongated with numerous lobes. At anthesis the pollen is bicellular, but about 2 % of tricellular grains occur a mong the pollen grains released from the anthers as well as on both na turally or handpollinated stigmas. Pollen germination is low in vitro, but higher in vivo. The pollen tubes are of normal shape. An electron -dense surface coat is sometimes visible on the exine, which in many c ases, is detached from the exine. The vegetative cytoplasm is very ric h in glycolipid bodies surrounded by endoplasmic reticulum. The genera tive cell has a lobed cell wall and is surrounded by the vegetative nu cleus.