Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

How flowers use scent and nectar to manipulate pollinators and herbivores

09.07.2015

Some pollinators not only provide fertilization services for flowering plants, they also lay their eggs on the plants’ leaves after they have visited the flowers. Voracious caterpillars hatch from these eggs. Scientists from the Max Planck Institute for Chemical Ecology in Jena, Germany, demonstrated in field trials that natural variations of scent biosynthesis and nectar secretion in wild tobacco populations ensure that the reproductive success is optimized while caterpillars are kept at bay. For the first time, scientists examined these two floral traits, scent and nectar, and their influence on pollen vectors and herbivores simultaneously.

Some pollinators not only provide fertilization services for flowering plants, they also lay their eggs on the plants’ leaves after they have visited the flowers. Voracious caterpillars hatch from these eggs and their enormous appetite can easily kill the plants. So when plants advertise for pollinators they frequently also attract herbivores. Scientists from the Max Planck Institute for Chemical Ecology in Jena, Germany, demonstrated in field trials that the flowers of the coyote tobacco Nicotiana attenuata are able to solve this dilemma.


The hummingbird Archilochus alexandri visits a tobacco flower. The little bird also pollinates coyote tobacco.

Danny Kessler / Max Planck Institute for Chemical Ecology

The researchers showed that when flowers produce both scent and nectar and are visited by three different pollinators, their outcrossing increases, which is important for the gene flow between plants. Moreover, both floral traits influenced oviposition by the hawkmoth Manduca sexta, with the amount of nectar being even more influential than floral scent on the decision of female hawkmoths to lay eggs. Natural variations of scent biosynthesis and nectar secretion in wild tobacco populations, including plants whose flowers do not produce any nectar at all, may therefore ensure that the reproductive success is optimized while herbivores are kept at bay.

For the first time, scientists examined these two floral traits, scent and nectar, and their influence on pollen vectors and herbivores simultaneously. (eLife, July 2015).

Flowering plants emit odors in order to attract pollinators. Pollinators are rewarded with sweet nectar for their reproductive assistance. However, this interaction is not always based on the “one hand washes the other” principle alone. Some female moths pollinate the flowers and lay their eggs on the leaves of the same plant afterwards. From these eggs, voracious larvae hatch and threaten the survival of the plant. One example of a ‘”mutualist turned into antagonist” is the tobacco hornworm Manduca sexta, a moth that visits the flowers of Nicotiana attenuata, a wild tobacco species in North and Middle America. Its larvae, however, can cause devastating feeding damage.

As scientists led by Ian T. Baldwin found out, the concentrations and amounts of floral scent and nectar vary in natural populations of Nicotiana attenuata. There are even individual plants that do not secrete any nectar at all. These plants cheat floral visitors by attracting them in the first place, but denying a reward for pollination services. In order to uncouple the influence of floral scent and nectar and to study both traits simultaneously, the scientists used plants that had been genetically altered to not produce benzylacetone, the main component of the floral scent, or nectar. A third group of plants could neither synthesize benzylacetone nor nectar. These plants were modified by using an RNA-interference-based transformation technique (RNAi). Both floral traits were studied simultaneously and independently for the first time.

The researchers examined the influence of these floral traits on outcrossing rates after pollinations by three different pollinators: the tobacco hawkmoth Manduca sexta, the hummingbird moth Hyles lineata, and the hummingbird Archilochus alexandri. A high outcrossing rate is achieved when pollen, and thereby the genetic information of a plant, is transferred from one plant to another. This increases genetic diversity in plant populations.

While nectar is a sweet reward that makes pollinators fly from flower to flower, floral scent is an attractant that advertizes the presence of this reward. The assessment of the experimental data revealed that both scent and nectar make sure that flowers are visited by pollinators more often than plants that lack these traits. Interestingly, scent and nectar had different effects on the pollen transfer service by the three tested pollinators. On the other hand, scent as well as nectar directly influenced oviposition by female Manduca sexta moths. The amount of nectar more than scent affected the decision of female moths to lay their eggs and therefore more Manduca eggs were found on plants that produced large amounts of nectar.

The scientists were surprised that nectar secretion had a larger impact on the egg-laying behavior in female Manduca sexta moths than did floral scent. They hypothesize that hawkmoths use nectar as an indicator to evaluate plant size or health traits which give their offspring a better chance of survival. “Some plants, one the other hand, are cheaters and only feign the presence of a reward. They benefit from nectar producing neighbors and cheated pollinators, thereby substantially reducing herbivory,” Danny Kessler, the first author of the study, explains.

Flowers face many challenges. They have to provide for outcrossing and reproductive success and depend on different pollinating species, all of which have different preferences and behaviors. At the same time, flowers must also make sure that moths won’t lay too many eggs on the plant’s leaves. “Both herbivores and pollinators contributed to the evolution of floral traits. Therefore it makes little sense to study these traits, scent and nectar, as if they only mediate pollination services,” Ian T. Baldwin, the head of the Department of Molecular Ecology, summarizes. His lab developed a comprehensive molecular tool box for the coyote tobacco Nicotiana attenuata.

The combination of these floral traits, scent biosynthesis and nectar production, requires a certain fine-tuning to maximize the fitness of a plant. Large moths, such as Manduca sexta, are probably able to transfer pollen over larger distances in comparison to hummingbirds which are usually found in the vicinity of their nests. Because wild tobacco populations are often found isolated in nature, the transfer of pollen over larger distances is important to ensure outcrossing between these populations. [AO/DK]

Original Publication:
Kessler, D., Kallenbach, M., Diezel, C., Rothe, E., Murdock, M., Baldwin, I. T. (2015). How scent and nectar influence floral antagonists and mutualists. eLife. doi:10.7554/eLife.07641.
http://dx.doi.org/10.7554/eLife.07641

Further Information:
Danny Kessler, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, +49 3641 57-1126, E-Mail dkessler@ice.mpg.de
Ian T. Baldwin, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, +49 3641 57-1101, E-Mail baldwin@ice.mpg.de

See also “Life outside the lab - Scientists in the field to take over eLife’s Twitter account” on http://elifesciences.org/elife-news/Science-outside-the-Lab-eLifes-Twitter-accou...

Contact and Image Requests:
Angela Overmeyer M.A., Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, +49 3641 57-2110, E-Mail overmeyer@ice.mpg.de

Download of high resolution images via
http://www.ice.mpg.de/ext/downloads2015.html

Angela Overmeyer | Max-Planck-Institut für chemische Ökologie

More articles from Life Sciences:

nachricht Shrews shrink in winter and regrow in spring
24.10.2017 | Max-Planck-Institut für Ornithologie

nachricht 'Y' a protein unicorn might matter in glaucoma
23.10.2017 | Georgia Institute of Technology

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Salmonella as a tumour medication

HZI researchers developed a bacterial strain that can be used in cancer therapy

Salmonellae are dangerous pathogens that enter the body via contaminated food and can cause severe infections. But these bacteria are also known to target...

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

3rd Symposium on Driving Simulation

23.10.2017 | Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

 
Latest News

Shrews shrink in winter and regrow in spring

24.10.2017 | Life Sciences

Microfluidics probe 'cholesterol' of the oil industry

23.10.2017 | Life Sciences

Gamma rays will reach beyond the limits of light

23.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>