Lowering their Heads and Facing East

Why do sunflowers behave this way?

Anyone who undertakes a train journey in late summer from Helsinki to Beijing (like I did quite some years ago), will see extensive fields of sunflowers before the train leaves Europe and enters Asian territory. What is remarkable about the sunflowers is that they all face one direction and observing that, I thought the sunflowers probably orient themselves towards the sun. But according to a recent study by Horvath and co-workers, this is not so, because following a short period of full bloom during which the flowers do orient towards the sun, they then gradually bend downward and become ‘locked’ in a direction to face the East. (Now the beautiful and patriotic song “The East is Red” 东方红, never mind the words, enters my head and reminds me of the time I heard it daily while spending 3 weeks in China by invitation of the Chinese Academy: you can guess how long ago that must’ve been!). However, sunflowers, which like many fruit and vegetable plants originated in the ‘New World’, have other reasons to turn eastward.

In the past, several reasons had been advanced to explain why after the flowering period sunflower inflorescences no longer track the sun, but remain east-oriented. Yet none have been tested reliably and the new explanation for the first time takes into consideration the place of origin of the sunflower plant, the astronomical data of the sun’s position, the meteorological data of diurnal cloudiness, the time-dependent elevation angle of mature sunflower heads and the absorption spectra of the inflorescence’s front and back. An earlier suggestion was that a non-skyward orientation of mature sunflower heads would make it more difficult for birds to peck at the seeds. While true, it does not explain why the flowers should face east. Another attempt to explain the eastward orientation was that it would reduce the heat load at noon, but west-facing flowers would have the same advantage, so why ‘east’? It has also been assumed that east-facing allows greater light reception in the morning and speeds up drying of morning dew, thereby reducing fungal attack. That an easterly orientation promotes attractiveness to pollinators has been suggested, but by the time the sunflower heads get ‘locked’ in the easterly position, pollination has long been finished and the idea that an easterly orientation and the lower head temperature could be advantageous for seed maturation was not supported experimentally.

What appears to be crucial is that there is a 10-50% surplus energy absorbed by an east-facing sunflower inflorescence compared with other directional orientations. This could indeed accelerate the evaporation of morning dew, but what is the easterly orientation due to? It has seemingly something to do with the region the sunflower plant evolved, namely Boone County in North America, which regularly encounters cloudy afternoons. If afternoons are cloudier than the mornings, then east-facing inflorescences have an energy advantage of around 10% over west-facing flowers and an up to 50% radiation excess over south-facing flowers, taking into consideration absorption spectra of the inflorescence and the back of the heads. Maximum radiation absorption should be advantageous for seed production and maturation. The easterly orientation seen even in domesticated European sunflowers is likely to be a genetic trait that evolved in response to the meteorologic conditions of cloudy afternoons in the region that sunflowers evolved in North America.

Given that solar panels are usually directed south and direct sunlight is most intense at noon, are sunflowers ill-adapted, or do sunflowers perhaps ‘know more’ than solar panel engineers? Sunflower heads are tilted, looking downward and under such conditions the lower angle of the sun in westerly and easterly position is crucially important. But adding afternoon cloudiness into the calculation is what then causes the East to turn into ‘the winning formula’ for Helianthus annuus (the sunflower).

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2021.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.

Studies that haven’t been done, but can and should be done

One of my weekly science blogs in the past had dealt with “Experiments that shouldn’t be done, can’t be done or can but won’t be done”, but I also think of studies that haven’t been done, can be done and should be done. Some (that I won’t disclose in this blog), I may be able to tackle myself in the future, others that I shall now mention are projects I’d love to carry out but for various reasons won’t be able to.

Honey bees, for example, are known to rather precisely visit flowers when they open in the morning and reveal their pollen and nectar sources. One can even teach bees to arrive at a feeding table at a particular time, e.g. 09.00 o’clock, to lap up a sugar solution reward. During spring in northern Finland the days get longer every day. Depending on the latitude the differences from day to day can be as big as 15 to 20 minutes during the maximal daytime lengthening period in March and April. Bees, we all know, are smart little insects, but can they anticipate time shifts? Once trained to receive food at 9.00 o’clock on day one, but then given food at 9.20 the next day, 9.40 the following, 10.00 the day after that, etc, i.e. with a 20 minute delay each successive day, would bees understand that food appears a little later every day? It would be remarkable if they could adjust to the constantly delayed feeding time and anticipate the correct time of feeding, appearing at the feeding station 20 minutes late each day.

My second project involves aquatic newts; vertebrates in other words that are famous for being able to regenerate severed body parts, including legs, parts of the tail, even an eye. But does “exercise” speed up the regeneration and healing process? If one surgically removes the last 1 cm of the tail of a number of identically long newts and keeps half of the operated animals in an aquarium with water filled to a depth of 2 cm, they would not have to swim to the surface to take a breath of air, but simply lift their head out of the water. The other half of the operated animals should also be kept in an aquarium, but filled with 25 cm deep water. If they want to take a breath of air, they’d need to swim to the surface and thereby use their now shortened tails for propulsion. My working hypothesis is that the newts which are forced to exercise their tails will experience a faster tail tip regeneration. And that could be interesting.

My third project is more involved and cannot be done by a single scientist. The idea for this project came to me a long time ago when I participated in the “Walther Herwig” fishery research expedition to the South Atlantic Ocean in 1967. When the ship crossed the so-called Walvis Ridge off the coast of Namibia, I studied the hydrographic charts, because I was interested in trying to catch some deep sea organisms with a special deep water net. The chart revealed that the submersed Walvis Ridge was a 3000 km long mountain range in an East-Southwest direction with multiple, deep canyon-like valleys, separated from neighboring ones by mountain ranges often 2 – 3,000 metres high as well as many seamounts mapped in 2012 by Oregon State University’s 2012 “R/V Melville” cruise MV1203. Obviously there was in the Walvis Ridge the possibility of rather isolated ‘pockets’ of very deep environments protected and shielded from neigbouring deep sea “valleys” by seemingly high barriers, sea mounts and guyots.

Not having followed up marine research in that part of the Atlantic, I cannot say for certain whether these “underwater valleys” have received any attention and whether, in fact, the hydrographic charts I had seen were reliable and correct. However, assuming they were representing the real situation, then I’d expect some unique benthic organisms in these deep underwater canyons and valleys. Pelagic fish can probably swim across the mountainous barriers, but organisms at the bottom? For them it would be harder. If I had the means, I’d organize an expedition to this part of the world to explore the “Deep Unknown in the Valleys of the Walvis Ridge” and recover treasures of hitherto unseen organisms!

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2021.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.

When yachts get colonized, it’s called biofouling

But who are the colonizers?

I have a friend in Finland, who owns a yacht, a big and costly one. And that means every weekend in the summer he’s got to go sailing and he has little time for anything else. A yacht is not exactly cheap and once you’ve got one you had better use it. Although this limits the choices you have to spend your weekends, there are two further aspects to consider (quite apart from choosing which kind of hull for your boat would be best): firstly, in winter the yacht has to be taken out of the water as the latter will be frozen for several months and secondly you need to make sure that not too many organisms settle on the hull. Paints to discourage the settlers can be applied, but once in a while the hull needs a cleaning.

Nowadays fibreglass boats are the most common around and they have, of course, the advantage over the more traditional wooden hulls that boring organisms have a much harder time to get into the fibreglass than into the wooden hulls. Collectively referred to as the ’infauna’ and exemplified by the feared shipworm (which is not a worm at all, but a kind of clam), the infauna used to be a dreaded problem, but the so-called epifauna (and flora) on the surface of the hull can also make the life of a sailboat owner a bit difficult. Not only will a luxurious growth of seaweeds and the presence of goose and related barnacles, bivalves, snails, sea anemones, sea squirts and a multitude of other organisms slow the vessel down, it is also not exactly cheap to get all these epibionts removed.

To what extent a ship gets colonized by which kinds of organisms depends on many factors: the material of the hull has already been mentioned, but salinity of the water and temperature are also very important. Whether the boat is stationary or moving is another factor and so is the shape of the hull and the ship’s draft. As with the body of a whale, colonized by a variety of epibionts, the success of a colonizer to remain attached to the hull of a yacht also depends where precisely the colonizer will best survive. Some species prefer the ship’s bow, others the stern near the propeller or the ship’s sides. What yacht owners often do not realize is that their unwanted epibiotic settlers can be passively transported by the boat to places where they had not been present before; in other words it is not only the ballast water that is usually held responsible for so many unwanted introductions of species here and there, but alien species can also be carried around on a ship’s hull.

A researcher with the beautiful name of Cristina Maria Rocha Farrapeira and her colleagues in Brazil have examined the hulls of 32 vessels and published their results in 2007. They did not look at the epifauna that would almost certainly have consisted of a variety of seaweeds and other algae with their own microscopic army of microorganisms, but they focused on identifiable and macroscopically visible animal species. Unsurprisingly, of the 60 species they found, 33 were crustaceans and of these 31 belonged to the Cirripedia, i.e. the barnacles and kin. Molluscs were the second most abundant creatures with bivalves (such as oysters and mussels) being responsible for eight species and snails for six species. Relatives of jellyfish and polyps were represented by three species and so-called moss animals (Bryozoa) and sea squirts (Urochordata) had two species each. In between the epibiontic organisms the researchers located flatworms, roundworms and seven species of segmented worms which like barnacles and molluscs attach themselves firmly to the boat’s hull and can only be removed by harsh scrubbing. If I now conclude that rather than owning a yacht myself, I prefer to be invited to take part in an occasional cruise, I think you’ll understand.

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2021.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.