Functional Morphology of the Lever Mechanism of Salvia pratensis

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2735310/

Abstract

Background and Aims

The functional morphology of Salvia pratensis flowers was re-investigated, after new insights revealed that pollen dispensing is one of the main functions of the staminal lever. In particular, no detailed information was available regarding the process of pollen transfer and the forces arising between the pollen-bearing thecae and the pollinating bee's body. The assumption was made that these forces play a significant role in pollen dispensing.

 

Methods

The functional morphology of S. pratensis flowers and the interaction between flowers and bees (Apis mellifera) were studied by reconstructing stress and strains by using qualitative and semi-quantitative theoretical analysis. Flowers were manipulated to study the spatial arrangement of the filament and lever, and of the head and proboscis of the visiting bee inside the tube. Photographs and films of bee visits on flowers were used to analyse the interaction of pollinator and staminal lever.

 

Key Results

The spoon-shaped lower lever of S. pratensis has a small hole through which a bee introduces its proboscis into the corolla tube. Although mentioned for the first time by Kerner von Marilaun in 1891, presented here is the first drawing and the first photograph showing this interaction in detail. The analysis of the interaction of flower visitor and the lever mechanism revealed that the position of bees on different flowers is spatially very similar. Flower morphology constrains postures of legitimately nectar-probing bees within narrow bounds. A theoretical discussion on structural elements and force progression in the flower allows the principles of lightweight architecture in flower morphology to be recognized.

 

Conclusions

The staminal lever of S. pratensis is a pollen-dispensing device. It seems to influence the amount of pollen deposited on pollinators by determining the forces arising between the pollinator and the pollen. The relevant forces occur either during the first, dynamic phase or during the second, almost static phase of a flower visit.

Key words: Flower–pollinator interaction, bee, Apis mellifera, pollination, pollen uptake, see-saw mechanism, biomechanics, pollen dispensing

 

 

 

 

Nectar guides & foraging

‘X’ marks the spot: The possible benefits of nectar guides to bees and plants

Functional Ecology

Volume 25, Issue 6, pages 1293–1301, December 2011

Orchid pollination: from Darwin to the present day

Abstract

In this year celebrating the bicentenary of the birth of Darwin and the sesquicentennial of the publication of Darwin's On the Origin of Species, the present paper aims to assess the impact of Darwin's legacy on the history of orchid pollination biology. To illustrate the major contribution of Darwin to this fascinating biological field, we focus on the large angraecoid orchid group and propose an overview of the complex relationships that these orchids have developed with specific pollinators. We further discuss how Darwin's seminal work on the angraecoid orchid Angraecum sesquipedale triggered the beginning of a long debate about the evolution of long floral spurs and why his idea of reciprocal evolution or ‘coevolution’ was one of the great contributions to evolutionary biology. 

Botanical Journal of the Linnean Society

Volume 161, Issue 1, pages 1–19, September 2009 

 

Floral Iridescence, Produced by Diffractive Optics, Acts As a Cue for Animal Pollinators

Abstract 
Iridescence, the change in hue of a surface with varying observation angles, is used by insects, birds, fish, and reptiles for species recognition and mate selection. We identified iridescence in flowers of Hibiscus trionum and Tulipa species and demonstrated that iridescence is generated through diffraction gratings that might be widespread among flowering plants. Although iridescence might be expected to increase attractiveness, it might also compromise target identification because the object's appearance will vary depending on the viewer's perspective. We found that bumblebees (Bombus terrestris) learn to disentangle flower iridescence from color and correctly identify iridescent flowers despite their continuously changing appearance. This ability is retained in the absence of cues from polarized light or ultraviolet reflectance associated with diffraction gratings. 

Full article


Science 2 January 2009:
Vol. 323 no. 5910 pp. 130-133
DOI: 10.1126/science.1166256 

The Origin of Modern Biodiversity: Coevolution of Flowers and Insects

Browsing the web, I came across this blog "Teaching Biology", where a very comprehensive description of coevolution of flowers and pollinators is presented!

I am not going to copy-paste the content on this post, so see the page using the link!


http://bioteaching.wordpress.com/

L'utopia tranquilla delle piante - The calm utopia of plants

sorry, in Italian only from the

Festival della Scienza di Genova

October 28, 2011

Stefano Mancuso

"Le piante hanno comportamenti sofisticati ed evoluti, una vita sociale meravigliosamente ricca e, in generale, una affascinante complessità che per millenni è rimasta sepolta sotto la loro apparente immobilità.
Mitezza contro violenza, fissità contro movimento, autotrofia contro eterotrofia, lentezza contro velocità: piante e animali sono il risultato di scelte evolutive opposte. Praticamente inermi, alla base della catena alimentare, eppure capaci di colonizzare la Terra fino a rappresentarne il 98% della biomassa, nella vita delle piante esiste un’idea utopistica e rivoluzionaria, che ne rende avvincente e imprevedibile il loro studio. Unici organismi viventi realmente "verdi" (in tutti i sensi), hanno evoluto strategie di comportamento così diverse da quelle degli animali da essere per noi una fonte inesauribile di originalissimi insegnamenti. Senza l’aggressività e prepotenza degli animali, senza la pressante necessità di uccidere per sopravvivere, le piante sono la realizzazione terrena del discorso della montagna: sono loro i miti che un giorno erediteranno la terra."

Watch the video here:
http://www.festivalscienzalive.it/site/home/conferenze/utopia-tranquilla-delle-piante.html

"Back to the past for pollination biology"

Manipulations of the interactions between plants and their floral visitors remain the most successful path to an understanding of floral traits, which may have been shaped by both herbivores and pollinators. By using genetic tools in combination with old-fashioned field work the dual protective/advertisement functions of floral traits are being realized. The distinction between wanted and unwanted floral visitors is blurring, and plants with specialized pollination systems are being found capable of using alternative pollinators if the specialized pollinators fail to perform.

Back to the past for pollination biology
Danny Kessler, Ian T Baldwin,
Current Opinion in Plant Biology
Volume 14, Issue 4, August 2011, Pages 429-434
Biotic interactions 

A rainforest vine has evolved dish-shaped leaves to attract the bats that pollinate it

Tests revealed that the leaves were supremely efficient at bouncing back the sound pulses the flying mammals used to navigate.

When the leaves were present the bats located the plant twice as quickly as when these echoing leaves were removed.

A team of scientists in the UK and Germany reported its findings in the journal Science.

The study is the first to find a plant with "specialised acoustic features" to help bat pollinators find them using sound.

Most bats send out pulses of sound to find their way around; the way they sense objects in their environment by sensing how these pulses bounce off them is known as echolocation.

http://www.bbc.co.uk/nature/14328999

Examining The Hummingbird Tongue

Hummingbirds can extend their tongues great distances — in some cases the length of their heads — to retrieve nectar. Biologist Margaret Rubega, of the University of Connecticut, explains how the structure of the hummingbird tongue traps liquid, and the evolution tales tongues tell.


The hummingbird tongue is a fluid trap, not a capillary tube

Alejandro Rico-Guevara1 and Margaret A. Rubega
PNAS May 2, 2011

Abstract

Hummingbird tongues pick up a liquid, calorie-dense food that cannot be grasped, a physical challenge that has long inspired the study of nectar-transport mechanics. Existing biophysical models predict optimal hummingbird foraging on the basis of equations that assume that fluid rises through the tongue in the same way as through capillary tubes. We demonstrate that the hummingbird tongue does not function like a pair of tiny, static tubes drawing up floral nectar via capillary action. Instead, we show that the tongue tip is a dynamic liquid-trapping device that changes configuration and shape dramatically as it moves in and out of fluids. We also show that the tongue–fluid interactions are identical in both living and dead birds, demonstrating that this mechanism is a function of the tongue structure itself, and therefore highly efficient because no energy expenditure by the bird is required to drive the opening and closing of the trap. Our results rule out previous conclusions from capillarity-based models of nectar feeding and highlight the necessity of developing a new biophysical model for nectar intake in hummingbirds. Our findings have ramifications for the study of feeding mechanics in other nectarivorous birds, and for the understanding of the evolution of nectarivory in general. We propose a conceptual mechanical explanation for this unique fluid-trapping capacity, with far-reaching practical applications (e.g., biomimetics).

Louie Schwartzberg: The hidden beauty of pollination

Pollination: it's vital to life on Earth, but largely unseen by the human eye. Filmmaker Louie Schwartzberg shows us the intricate world of pollen and pollinators with gorgeous high-speed images from his film "Wings of Life," inspired by the vanishing of one of nature's primary pollinators, the honeybee.

An Orchid Explosion

Cool video showing another pollination system of orchids!
Watch it and let me know what you think!

Scent of death

The orchid Satyrium pumilum is able to attract insects by mimicking the smell of rotting flesh.
A new study comparing the scent of the orchids with that of roadkill is to be published in the Annals of Botany 

The author was puzzled by the shape of the flowers. They don't carry any nectar and even if they did, the spurs that would hold it are the wrong shape to feed any visitors. So how do they attract insects to pollinate their flowers?

Photos by Dennis Hansen