Some plants spike their nectar with nicotine to keep visitors moving
A wild tobacco from Utah lures birds and moths with a sweet scent, then laces its nectar with bitter nicotine. The likely payoff: a pollinator takes one sip, dislikes the aftertaste and flies on to another plant, spreading pollen further while the plant spends less sugar. Nectar is a bargaining tool, not a gift.
Nectar is a thick, sugary liquid made in glands called nectaries, mainly sucrose, glucose and fructose in varying mixes, plus amino acids, oils and scent compounds. The name comes from the Greek drink of the gods, possibly meaning unkillable; its use for the sweet liquid in flowers dates from AD 1600. Bees turn it into honey, and many predatory wasps rely on it as adults, then hunt crop pests to feed their young.
Inside flowers, nectaries can sit on almost any part, and their position is tuned to the visitor. Long-tongued moths, butterflies and birds reach nectar deep near the ovary, while short-tongued insects tend to find it on petals or sepals. Many flowers push nectar into a spur whose length helps decide who can drink. Snapdragon relatives have evolved petal spurs four separate times, apparently by recruiting the same pair of genes each time. Wind-pollinated plants, needing no couriers, often have no nectaries, and after pollination many flowers reabsorb what is left.
Nectar produced outside flowers usually serves as pay for bodyguards. Glands on leaves and stems attract ants and wasps that eat both the sugar and any caterpillars nearby; acacias and passion flowers use this defence. Charles Darwin thought such glands were mere excretory organs of no use to the plant. The Italian botanist Federico Delpino, one of his correspondents, argued otherwise in an 1886 monograph. These extrafloral nectaries are now known from more than 3941 species and appear to have evolved in at least 457 separate lineages, including 101 fern species.
Not every drinker plays fair. In Hawaii, where the long-billed honeycreepers that once pollinated certain lobelioids have gone extinct, cameras showed 39% of bird visits were nectar robbing, often by piercing the flower. Even so, the plants still set plenty of viable seed.
Source: Nectar
