CYTOLOGY OF 2N POLLEN FORMATION AND POLLEN MORPHOLOGY IN DIPLOID LOTUS-ENUIS (FABACEAE)

Two genotypes of Lotus tenuis Waldst & Kit. ex Willd. PI 204882, a dip loid (2n = 2x = 12), were identified as producing 2n pollen (maximum = 6%). The objectives of this research were: (1) to determine the mecha nism(s) of 2n pollen formation in the L. tenuis genotypes and (2) to m orphologically describe n and 2n pollen using light and scanning elect ron microscopy. Meiotic studies revealed that 2n pollen resulted from tripolar spindles during anaphase II of microsporogenesis. The 2n poll en germinated well, although abnormal pollen tubes were observed. The genetic constitution of 2n pollen resulting from tripolar spindles is equivalent to first division restitution (FDR) of meiosis. Fresh and a ir-dried pollen samples exhibited differences in size and shape under light and scanning electron microscopy. The size of diploid (2n) polle n was larger than that of haploid (ln) pollen. Normal haploid (ln) pol len was globose-prolate in shape, while diploid (2n) pollen was tetrah edral in shape.