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

 

 

 

 

Back to the future!

Plants back to life after 30.000 years:

Scientists in Russia have grown plants from fruit stored away in permafrost by squirrels over 30,000 years ago.

The fruit was found in the banks of the Kolmya River in Siberia, a top site for people looking for mammoth bones. The Institute of Cell Biophysics team propagated plants of Silene stenophylla in vitro from the fruit tissues.

the full news on BBC News

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 

 

PLANT-MEDIATED INTERACTIONS BETWEEN ABOVE- AND BELOW-GROUND COMMUNITIES

http://onlinelibrary.wiley.com/doi/10.1111/jec.2010.99.issue-1/issuetoc

Special Issue
Journal of Ecology

Ant-Plant Mutualism

 

 

Summary

1.  Mutualistic interactions are characterized by conditional outcomes that depend on both the biotic and the abiotic context. However, limited information is available on the factors that affect the strength of ant–plant interactions among sympatric congeneric species.

2.  We compared the benefits gained from attracting ants via extrafloral nectaries – i.e. lowered herbivory and increased seed set – of three co-occurring varieties in the Chamaecrista desvauxii complex (Leguminosae) in a cerrado area in Uberlândia, Brazil. Using whole-individual exclusion experiments, we tested the hypotheses (i) that the relative strength of those benefits is higher in the variety with the largest extrafloral nectaries and (ii) that those benefits are conditional on the presence of predispersal seed predators.

3. Extrafloral nectaries are larger, produce more nectar and attract more ants in var. brevipes than in the other two varieties included in the study. Var. modesta has intermediate-sized nectaries, while a third, undescribed variety has small nectaries, and both attract relatively few ants.

4. For var. brevipes, extrafloral nectary (EFN) removal significantly increased folivory and attack on fruits by sucking insects, decreasing the relative number of flowers, fruits and seeds produced per individual. For the other two varieties, in contrast, ant effects were reduced, and ants did not significantly improve reproductive success. In addition, effects of EFN removal were less pronounced or absent when seed predators were excluded from fruits of var. brevipes.

5. Synthesis. We showed experimentally that benefits from interactions of three co-occurring varieties of Chamaecrista desvauxii with ants are context-dependent both within and among taxa. Variation in the strength of mutualisms among sympatric taxa may potentially reinforce ecological reproductive isolation and contribute to diversification in this group.

Journal of Ecology

Volume 100, Issue 1, pages 242–252, January 2012

The Seed Site

A website devoted entirely to seeds! 

Photographs
Seed Harvesting
Seed Sowing
Germination
Seedling Images
Database
Plant Profiles
Plant Index

http://theseedsite.co.uk/

Pflanzen als Vorbild für Roboter

http://www.heise.de/newsticker/meldung/Pflanzen-als-Vorbild-fuer-Roboter-1429208.html

On the German news, Plants as model samples for robots!!

How do wines coil around a support?

and how do seeds bury themselves into the ground?

A Clearer View from Fuzzy Images

Rather than having a single layer of photoreceptor cells, these eyes have a multitiered retina with four distinct photoreceptor layers. Nagata et al. investigated the spectral sensitivity of these retinal layers using a combination of molecular biology and electrophysiology. Opsins, a group of genes coding for specific color sensitivity (8, 9), were identified in the four retinal layers by gene sequencing, expression analysis, and in situ hybridization. Electrophysiology revealed that layers 1 and 2 are maximally sensitive to green light, whereas layers 3 and 4 are maximally sensitive in the ultraviolet. These sensitivities matched the identified opsin genes in the retinal layers. Curiously, however, even though layers 1 and 2 contain primarily green-sensitive photoreceptors, the effect of chromatic aberration means that incoming green light is only clearly focused on layer 1. This means that the second main green-sensitive retinal layer (layer 2) receives a defocused or “fuzzy” image. Nagata et al. suggest that the spiders obtain depth cues from the amount of defocus in this layer, which is proportional to the distance of the object to the lens.

Science 27 January 2012:
Vol. 335 no. 6067 pp. 409-410 

Depth Perception from Image Defocus in a Jumping Spider

Abstract

The principal eyes of jumping spiders have a unique retina with four tiered photoreceptor layers, on each of which light of different wavelengths is focused by a lens with appreciable chromatic aberration. We found that all photoreceptors in both the deepest and second-deepest layers contain a green-sensitive visual pigment, although green light is only focused on the deepest layer. This mismatch indicates that the second-deepest layer always receives defocused images, which contain depth information of the scene in optical theory. Behavioral experiments revealed that depth perception in the spider was affected by the wavelength of the illuminating light, which affects the amount of defocus in the images resulting from chromatic aberration. Therefore, we propose a depth perception mechanism based on how much the retinal image is defocused.  

Science 27 January 2012:
Vol. 335 no. 6067 pp. 469-471 

 

Bless you! - Gesundheit! - Salute!

"Bless you"

"Salute"

!!!!!!!!!!

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/