Tobacco plant thwarts caterpillar onslaught by opening flowers in the morning

Jan 21, 2010
Wild tobacco (Nicotiana attenuata), native in North America, is flowering during the nighttime and attracts night-active moths as pollinators by emitting the attractant benzyl acetone. However, as soon as female moths start laying their eggs on the plant and the young caterpillars become a serious danger, the plant postpones the opening time of the flowers by 12 hours to dawn and additionally stops producing benzyl acetone. Moths stay away and hummingbirds take over pollination. Credit: Danny Kessler, Max Planck Institute for Chemical Ecology, Jena, Germany

We normally think of pollinators as providing a valuable service to plants, and they certainly do. In exchange for nectar, pollinators like the well-known honey bee carry pollen from one plant to the other and thus promote cross-fertilization. But what happens when the pollinators aren't satisfied with their nectar rewards and decide to eat their generous plant partners? Just such a scenario arises in a number of plant-pollinator mutualisms in which the pollinator deposits eggs on the plant, which then develop into herbivorous larvae. What is a plant to do when faced with such a dilemma?

As reported online on January 21st in , a Cell Press publication, Ian Baldwin and colleagues have discovered an ingenious solution to this problem by studying the pollination of a wild tobacco species living in the Southwestern United States. This , Nicotiana attenuata, normally opens its flowers at night, during which it is visited, and pollinated, by the night-active hawkmoth. In exchange for transferring pollen, the hawkmoth is provided with a sugary reward. Such a quid pro quo relationship would seem to be all fine and dandy for N. attenuata, but as it turns out, the hawkmoth also likes to lay its eggs on the plant—eggs that develop into voracious, leaf-eating caterpillars.

This is obviously not an ideal outcome from the plant's perspective. But N. attenuata has an interesting trick up its sleeve. Stimulated by oral secretions released by the munching , N. attenuata performs an astonishing change in flower phenology (the timing of flower opening) in which the flowers open in the morning instead of at night. This change in flower phenology, as well as other alterations, including a in flower shape and the loss of key chemical attractants, leads to a switch in from the hawkmoth to a local hummingbird. The latter, unlike the hawkmoth, is normally active during the day and seems to be satisfied with just a nectar treat.

Of course, these observations raise the question of why N. attenuata bothers producing night-opening flowers that attract hawkmoths in the first place. Why not just focus on luring hummingbirds? Baldwin and colleagues don't know the answer to this question, but it's possible that the hawkmoth, for all its faults, might be a more reliable and effective pollinator than the .

Looking to the field of plant-pollinator interactions more generally, the findings have some potentially broad implications. For one, plants face another dilemma, related to the one described by Baldwin and colleagues, in which traits that attract a pollinator can also attract herbivores, resulting in an inevitable trade-off. Thus, one wonders whether herbivore-induced changes to flower phenology could be used more generally to mitigate the unwanted side effects associated with flowers that are attractive to both pollinators and herbivores. Also, in studying how the caterpillars' oral secretions induce the switch in flower phenology, Baldwin and colleagues discovered that a chemical pathway crucial to many defense responses in plants is required. The role of such a common defense pathway raises the interesting possibility that the effects of herbivore attack described in the study may be common in plants.

Taken as a whole, the findings highlight the remarkable adaptability of plants to changing circumstances and the complex, sometimes contentious, relationships between plants and their pollinators.

Explore further: Rare new species of plant: Stachys caroliniana

More information: Danny Kessler; Celia Diezel; Ian T Baldwin: Changing pollinators as a means of escaping herbivores. Current Biology, Online First, January 21, 2010, DOI 10.1016/j.cub.2009.11.071

Related Stories

Nectar is not a simple soft drink

Feb 27, 2007

The sugar-containing nectar secreted by plants and consumed by pollinators shares a number of similarities to fitness drinks, including ingredients such as amino acids and vitamins. In addition to these components, nectar ...

Probing Question: Why are flowers beautiful?

Jan 24, 2008

In the 1930s, American artist Georgia O'Keefe wrote: "What is my experience of the flower if it is not color?" O'Keefe is best known for her vibrantly colorful close-ups of petals and stamens on large canvases.

Study of flower color shows evolution in action

Jun 29, 2009

Scientists at UC Santa Barbara have zeroed in on the genes responsible for changing flower color, an area of research that began with Gregor Mendel's studies of the garden pea in the 1850's.

New research explains orchids' sexual trickery

Dec 17, 2009

A new study reveals the reason why orchids use sexual trickery to lure insect pollinators. The study, published in the January issue of The American Naturalist, finds that sexual deception in orchids leads to a more effici ...

Recommended for you

Rare new species of plant: Stachys caroliniana

Nov 21, 2014

The exclusive club of explorers who have discovered a rare new species of life isn't restricted to globetrotters traveling to remote locations like the Amazon rainforests, Madagascar or the woodlands of the ...

Mysterious glowworm found in Peruvian rainforest

Nov 21, 2014

(Phys.org) —Wildlife photographer Jeff Cremer has discovered what appears to be a new type of bioluminescent larvae. He told members of the press recently that he was walking near a camp in the Peruvian ...

The unknown crocodiles

Nov 21, 2014

Just a few years ago, crocodilians – crocodiles, alligators and their less-known relatives – were mostly thought of as slow, lazy, and outright stupid animals. You may have thought something like that ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.