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Flowers

November 1, 2013

Our home library was one information resource I had in childhood in those dim days before the Internet. My father had taken some introductory college courses funded by the GI Bill before he decided to follow his own father's profession as a carpenter/contractor. For that reason, I had a college chemistry textbook, along with some mathematics textbooks, at hand in my own house.

An old family photo, c. 1926

My father (center), with two of his three sisters,
circa 1926.

Will your digital photos survive for 87 years?

DVDs have an assured lifetime of less than fifteen years)


Some of the chemical terminology confused me, one example being "flowers of sulfur." I knew that sulfur was a foul-smelling chemical, so how could it be associated with sweet-smelling flowers? As it turns out, the petal-like quality of the flakes of sulfur in this sublimed form of sulfur is the reason for the name.

Flowers exist as a way to entice insects to help with pollination, so we wouldn't expect to find flowers in the geologic record until after the time of the first insects. The earliest evidence of an insect, the Rhyniognatha hirsti, is found in the Rhynie chert, a sedimentary deposit dated to the Devonian period, which extended from about 420-360 million years ago.[1]

Rhyniognatha hirsti is not that simple an insect, since it has characteristics in common with winged insects; so, it's reasonable to assume that insects first appeared at an earlier time, probably in the Silurian period, which extends as far back as 445 million years ago.[1] A large radiation of insects, the beetles, occurred about 300 million years ago, and flying insects appeared about 250 million years ago.

Peter A. Hochuli, a paleontologist at the University of Zürich (Zürich, Switzerland) and Susanne Feist-Burkhardt, a consulting geologist in Ober-Ramstadt, Germany, have just published a paper with evidence that flowering plants appeared at least as early as the Middle Triassic period, about 247.2-242.0 million years ago.[2-3] Their evidence is the discovery of fossil pollen grains in northern Switzerland, at two core-drilled samples from Leuggern and Weiach (see map). Pollen grains are small, robust and numerous, so they fossilize more easily than other plant parts, such as leaves and flowers.

A map of Northern Switzerland

Core-drilling sites at Leuggern and Weiach in northern Switzerland.

(Fig. 1 of ref. 2, published under a Creative Commons License.)[2)]


Previously, fossilized pollen from flowers was found in the geologic record only since the Early Cretaceous, about 140 million years ago, so that time has been the earliest known for the existence of flowers. The present study pushes this date back 100 million years earlier.[3]

The pollen grains found in the Northern Switzerland core samples are much like those of early angiosperm (flowering plant) pollen of the Early Cretaceous, except for their having an extremely thin inner layer.[2] Six pollen types were identified using Confocal Laser Scanning Microscopy, and sedimentological evidence suggests a wide ecological range for these plants.[2]

Middle Triassic pollen.

Middle Triassic pollen grains found in northern Switzerland. These grains were recovered from the Weiach core sample at 950.82 meters (left) and 903.02 meters (right). The size of the left specimen is 32.0 x 46.0 μm, and the size of the right specimen is 31.5 x 41.5 μm. (Image sources, left and right, Peter A. Hochuli and Susanne Feist-Burkhardt, University of Zürich )


These data confirm a 2004 study by these same authors in which Middle Triassic pollen was found in cores from the Barents Sea, south of Spitsbergen. Says Hochuli, "We believe that even highly cautious scientists will now be convinced that flowering plants evolved long before the Cretaceous."[3]

As we fast-forward to the modern era, we find that bees, prolific pollinators that evolved about a hundred million years ago, are in decline for many reasons. A recent study by scientists at the University of Southampton (Southampton, UK) has revealed another problem for bees. Nitric oxides found in vehicle exhaust diminishes bees' response to floral scents.[4-5]

In experiments, diesel exhaust exposure to a synthetic blend of floral chemicals significantly lowered the concentration of the scents, and it even rendered two scent components undetectable.[4] University of Southampton neuroscientist, Tracey Newman, an author of the study, is quoted by the BBC as saying,
"Bees need to decipher the chemical messages they're getting [from flowers] to be able to home in on the flowers they know will give the best yield [of nectar]."[5]
So, the hundred million year coevolution of the flower-bee ecosystem is being disrupted by a technology developed just a little more than a hundred years ago.

References:

  1. Michael S. Engel and David A. Grimaldi, "New light shed on the oldest insect," Nature, vol. 427, no. 6975 (February 12, 2004), pp. 627-630.
  2. Peter A. Hochuli and Susanne Feist-Burkhardt, "Angiosperm-like pollen and Afropollis from the Middle Triassic (Anisian) of the Germanic Basin (Northern Switzerland)," Front. Plant Sci., vol. 4, no. 344 (October 1, 2013), doi: 10.3389/fpls.2013.00344.
  3. New fossils push the origin of flowering plants back by 100 million years to the early Triassic, University of Zürich Press Release, October 1, 2013.
  4. Robbie D. Girling, Inka Lusebrink, Emily Farthing, Tracey A. Newman and Guy M. Poppy, "Diesel exhaust rapidly degrades floral odours used by honeybees," Scientific Reports, vol. 3, article no. 2779 (doi:10.1038/srep02779, October 3, 2013).
  5. Victoria Gill, "Bees' foraging for flowers 'hampered by diesel exhaust'," BBC News, October 3, 2013.

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