Honeybees are poor pollinators — why?

Contrary to most other bee species honeybees are highly eusocial and hold extremely long-lived societies. Their all-season activities force them to use whatever plants available and prevent any specific adaptations — in the flowers, in honeybees, and in all competing bees. This flexible behaviour in flowers has been a precondition for perennial colony life. But as bees evade becoming contaminated by pollen their visits often do not result in pollination. Honeybee monocultures thus must be avoided by all means.     

Hummingbird Pollination in Two Species of Vellozia (Liliiflorae: Velloziaceae) in Southeastern Brazil*

Pollination by hummingbirds was observed in two species of Vellozia (Velloziaceae) in southeastern Brazil. Both species have purplish-pink to dark purple tepals, tube-like arrangement of stamens, large and protected nectar chamber, and no odour. Tepals are reflexed in V. leptopetala and narrow in V. declinans, further enhancing the tube-like effect given by the long yellow anthers. Nectar is very dilute (ca. 10%). Three species of hummingbirds were observed pollinating these Vellozia species: Colibri serrirostris, Augastes scutatus, and Chlorostilbon aureoventris. The first species established feeding territories in the vicinity of V. leptopetala flowers. A bee-pollinated Vellozia flower-type may give rise to a hummingbird-flower by relatively simple adjustments, consisting mainly of the reflexion of tepals, increase in stamen length, enhancement of reddish pigments, enlargement of nectar chamber and dilution of nectar. Vellozia declinans may be likened to one of the hypothetical stages of this trend towards ornithophily, whereas V. leptopetala is possibly one of the extremes within the genus.     

Flower production,male sterility and berry setting in andigena potato

Summary Unlike tuberosum, andigena potato germ plasm exhibits a high degree of genetic variation in morphological, biochemical and reproductive traits. Sixty-five percent of the 565 genotypes comprising 145 accessions of Solanum tuberosum ssp. andigena obtained from Argentina, Bolivia, Chile, Colombia and Peru remain totally vegetative and never develop any floral bud when cultivated in northern India. In 18% of genotypes, the floral buds develop but they drop off from the plants prematurely. Thus, 83% of genotypes do not develop mature flowers. The frequency of such genotypes is maximum in the Bolivian genotypes. Whereas 17% of genotypes produce mature flowers, only 2% develop berries. The highest proportion of floral bud formation and their subsequent development and differentiation into mature flowers occur in Peruvian and Colombian genotypes. Partial to high male sterility occurs in 93% of the flowering genotypes; their pollen sterility ranges from 15% to 91%. Seven percent of the flowering genotypes are completely pollen sterile. The male sterility is expressed variously, ranging from structural to sporogenous types. The floral bud formation, its development and retention to maturity, pollen and ovule functionability and fruit development are under the control of a large number of genes, most of which are unlinked and independent. Many of these genes are polygenic in nature.