Guess What’s Being Described

spy-silhouetteThis is the second in a series in which clues are given and the reader is left to guess what is being described.

The mystery is something fairly common in my neck of the woods and in many other places on the planet. Yet you would not see it at the bottom of any ocean. Sometimes a railroad track is all that separates a rich area from a poor neighborhood. In this case, another type of barrier separates those who commonly see the mystery and those who don’t. If the proximity of such a barrier is visited by a cold current, you will experience even less of it on the wrong side of the barrier.

Often you only experience its refreshing smell in the first five minutes. And then it fades like a fragrance does when you distance yourself from a peony. If at its widest point it is no thicker than a human hair, it will not move faster than a spider. Otherwise if the mystery is half a centimeter in size, it will move as fast as the average dog. But if it gets slightly bigger than that, its moving shape will no longer be that of a hamburger bun. Instead it will break up into tiny little spheres, which could grow again.

It can become coated with layers of ice but only in the summer. When conditions are not so humid, if the mystery falls near very dry air, the mystery will take energy away from it, and cool it to the point that the air will rapidly descend . The rapid movement has crashed 5 planes in a recent decade.

What we have in mind cannot be born without dust, pollen or non sea-salt SO42- particles. Even in a world without pollution, there would be an acid in the mystery, albeit one of a different nature, thanks to respiration. Even if the Garden of Eden existed, the addition of carbon dioxide from the breath of Adam and Eve would cause the mystery to pick up ions from rocks and wash them into sea. In other words, it would still be one of two mechanisms that makes the oceans salty.  When mass-volcanism and— especially— humans don’t inject excess amounts of carbon dioxide into the atmosphere, the mystery, along with oceans helps keep the amount of carbon dioxide at steady state.

Can you  guess what’s being  described?

 

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Not Yawning at Pure Science

The world would be a different place if more people valued science, even as a hobby. In the same way that cities invest heavily in building indoor pools and artificial turf for amateur swimmers and soccer players, respectively, a society that relishes science for curiosity’s sake would alternately build centers for amateur research. The thought was inspired by a doctor’s answer to a radio listener’s question about yawning:

Unfortunately there’s not much research into finding out why people yawn. It would need a lot more work in the areas of psychology and group behavior, but there is not much interest in it. A lot of the granting agencies would probably consider the field a big yawn 1.

YawnWhy should we be enslaved to doing research only for what tickles the fancy (or serves the interests) of sponsors and agencies? And why should practicing science only be for those who get paid for it? I find yawning a great subject and the modest knowledge we’ve gained about the topic was enough to awake me this morning. But as interested as I was in the topic, due to the mysterious contagious nature of yawning, while I read less than 500 words, I yawned no less than four times.

Ultrasounds reveal yawn-like behavior during the first 3 months of development in the womb, suggesting that it goes far back in our evolution. The notion that it was a warning to predators is a pure guess and probably a wrong one. Something that triggers more questions and which is more substantial is the fact that two different neurotransmitters, dopamine and serotonin, increase the frequency of yawning. The experiments were done on rats, and since dopamine does not cross the blood brain barrier, a researcher either has to use a dopamine precursor such as L-dopa or an agonist—a compound that triggers the same receptors. From what I could gather, they used apomorphine, an agonist for two of the 5 known receptors of dopamine.

apomorphine

The above structures reveal the similarities between the two molecules. Apomorphine is synthetically derived from the biologically produced morphine by treating the opium- product with phosphoric acid. Morphine’s protruding OH group gets dehydrated by the acid, which rearranges the structure to that of apomorphine.

Compounds that fail to do likewise include CO2 and O2. Increasing either gas in the air we breathe has no effect on how often we yawn, which puts a major dent in the hypothesis that yawning is induced by a change in the composition of air.

Physiologically, a  morning yawn differs from a yawn in the evening. The former spreads beyond the face, as if to help awaken us. A night- yawn is more localized, and maybe its role is simply to prepare us for sleep. I’m guessing that if members of a social group share the same shelter it may be advantageous if a behavior helps others reach a state of alertness in the morning and a period of needed rest at night. That could explain the contagiousness of yawning.

Five hours after I’ve awakened, just writing about yawning has induced two more yawns on my part. How many on yours?

1 Irvin Mayers, Catching the Common Yawn, The Quirks and Quarks Question Book. 2002. CBC

What Flows In and Out of Phloem

This week, our city employees cut a diseased tree on my street. You couldn’t design a better experiment to map the location of phloem in a tree! Just look at where the ants are gathering, and that thin ring of congregation adjacent to the bark is above the plant tissue responsible for the transport of sugars from leaves to roots. antsPhloem

How did we first learn about the composition of sap or of its location in plants?

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Aphid  excreting a droplet of honeydew. Source: amada44 Wikipedia

If someone parks a car (or a bike 🙂 ) under a tree in the middle of summer, it could end up being covered with a gluey residue. This substance known as honeydew is a product of phloem-feeding insects such as aphids, whiteflies and scale insects. Members of most aphid species inject their stylets into the sieve tubes of phloem. The sap moves through the small insect’s digestive system and comes out of its posterior end as that sticky product, which not only frustrates parkers but alerts parasites and predators of aphids.

If you analyze the contents of the stylet, you gain insight into what flows through phloem: phloemwater0275 to 90% water, with its main solute being sugar along with small amounts of amino acids and alkaloids. If it seems that aphids are wasting sugars by excreting them, it’s because of sap’s low nitrogen content (from amino acids) that a lot of the main solute is excreted. The aphids need to ingest a large amount of sap to get enough nitrogen to make protein, and in the meantime they have no use for all the excess sugar.

In other experiments from the past century, bean leaves were exposed to artificial carbon dioxide containing only the radioactive isotope of carbon, 14C. About half an hour later, sugars carrying carbon-14 were found in the phloem’s sieve elements. This is how we first gained solid evidence that some photosynthetic products from leaves are shared via specialized vessels and sent towards the roots.

Some ants live mutualistically with aphids, and the relationship is remarkably sophisticated. The ants spread the  aphids and protect them in exchange for the sugars in their honeydew. Some aphids cannot excrete unless they are stroked by the antennae of their farming ants. In certain cases, ants will strip developing wings from aphids not to lose their herd. The ants can also release compounds that slow down aphids’ walking speed. Even slight differences between honeydews in the quantity of plant secondary compounds and in the composition of sugars affect the behavior of honeydew-feeding ant colonies.

Other Source:

Raven, Evert and Curtis. Biology of Plants. 2nd Edition