Category Archives: energy

Heterotroph Denial

Alright readers, I have a lot to do today, but I feel compelled, nay, obligated to blog about something buzzing around the interwebz lately. Remarkably, no- this isn’t about plants or algae or any other autotroph. Confused since this is an all-autotroph blog? After reading a news article that Ukrainian model Valeria Lukyanova believes she can subsist on only air and sunlight, I have to set the record straight. Let me say this slowly so there is no confusion and please feel free to share this with your friends.

You. Are. Not. Photosynthetic.* Humans are heterotrophs. Full Stop.

It’s really important to me that you know this.

I hope that some of the links on my Basics page will explain why this ‘Breatharian’ lifestyle is crazy. Yes, sunlight is the main source of energy feeding into the Earth’s biosphere. This makes the sun both physically important to our survival and an intimate part of our human culture. The sun is critically important to the way we live because our lives depend on photosynthetic organisms. This is because truly photosynthetic organisms have biochemical machinery that can capture and convert the sun’s energy into useful energy storage molecules (ATP, NADPH, glucose). Even photosynthetic organisms require water for this process. Why do you think people get so up in arms about droughts?

Let’s consider the implications of a Breatharian reality.  If Breatharianism were possible, then why are there more than 800 million food-insecure people around the globe? Surely, they have access to sunlight. Should we just tell them to quit complaining and enjoy their sun? If this were the case, then agriculture is the biggest con of all time. So, let’s just not do it anymore. The food service industry is just profiteering off of the heterotrophic hoax as well. This conspiracy was all masterminded by some elite group of gardeners**, hunters and herders that swindled early humans into buying otherwise worthless crops, meat and dairy. Once the human population was hooked on the delicious calories, those robber barons have been laughing all the way to the bank. I’m quite sure that must’ve been how it all went down.

A brief on-line search reveals that Valeria is not the only adherent to this practice. Sigh. Sure, the human body is amazing and can endure periods of time without food and water, but our bodies cannot survive indefinitely without them. Check out the video below for a breakdown of what happens on a Breatharian lifestyle (aka dehydration and starvation).

I know I’ve mentioned KungFu Panda before, but this scene is worth mentioning today:

Tigress: It is said that the Dragon Warrior can survive for months on nothing but the dew of a single ginkgo leaf and the energy of the universe.

Po: I guess my body doesn’t know it’s the Dragon Warrior yet. I’m gonna need a lot more than dew and universe juice.

Yeah, Po. Me too.

Fasting is a common religious practice, but believing that one could solely subsist on sunlight and air as a lifestyle choice is just downright heterotroph denial. This post topic gets a special new category for blog posts here (head-desk). Respect what real photosynthetic organisms are doing for you today… and eat one of them. Then wash it down with the aqueous solution of your choice. I really hope we don’t have to cover this again.


* Not even those sea slugs turned out to be photosynthetic. They looked like leaves crawling around the ocean floor. Srsly? What makes you think you will fare any better. Heterotroph = you have to eat something else.

** Yes, I seem to remember something about this in the Master Gardner handbook. Oops, I guess I let the cat out of the bag. Guess I won’t be getting my new card this year.

References and Links:

The Twelve Days of Christmas Plants: Poinsettias

This series of posts will highlight the plants that help you celebrate the Yuletide season.


Poinsettias (Photo credit: agrilifetoday)

Today we’re talking poinsettias. How many facts do you know about the flower? First of all, poinsettias are known by many names. The Latin name Euphorbia pulcherrima translates as ‘most beautiful.’ They were first known as Cuetlaxochiti by the Aztecs in their native Mexico. Today they are known as “La Flor de Noche Buena” or Christmas Eve flower. We call them poinsettias in America because they were first introduced to the United States in 1825 by Joel Roberts Poinsett, the first Minister to Mexico.

While we’re on the subject of nomenclature, what we normally think of as poinsettia flowers aren’t really flowers at all. Here’s your plant science word of the day: bract. They may look like colorful petals, but they are actually specialized leaves associated with the much smaller ‘actual poinsettia flowers’. The fortuitous combination of intense color with seasonal timing has led to the popularity of poinsettias at Christmas. The biology behind this timing involves short day photoperiodism. Remember the other day when I told you that plants know the day of the year by measuring the length of the night? That’s exactly what poinsettias do. Since they are a short day photoperiod plant, when the night is sufficiently long, a biochemical response is triggered to turn the bracts vivid colors.


Poinsettias (Photo credit: agrilifetoday)

The colorful bracts remain until the small yellow flowers* are pollinated, then the plant sheds them along with most of the other leaves. From the plant’s perspective, once pollination and seed production occurs, its work is done, and there is no need to keep up such showy attire. I’m sure many people just assume that they have killed their potted poinsettias by this point in their captivity, but that’s not always the case. You can keep your poinsettia plants alive for another round of flowering next Christmas season. Check out this link for the best cultural practices to do so. Just remember, whatever strategy you decide to use to induce coloration (cardboard box or enclosed room) make sure that you really give them 12 – 15 continuous hours of darkness. The plant will know if you open the door to the room or turn on the light in the closet to stash a Christmas gift.

Some of you may only want to tolerate your poinsettias for a single season, if that, because of the rumor that these plants are poisonous to people and pets. This is actually false. While they are not edible and ingestion may cause your pets and toddlers to yack all over your Christmas tree skirts, they are not toxic. Your pets and plants would have to ingest hundreds of bracts to cause death. The ancient Aztecs used the latex produced by the plant as a fever reducer. Of course, these plants are to be enjoyed for their visual aesthetics only, so it’s always safest to keep them out of tasting reach of your children and pets.


poinsettia (Photo credit: seven twenty five)

The majority of poinsettias are purchased during the six weeks leading up to Christmas, and they are big business in the floral industry. They account for ~$250 million in sales annually and are top the list in market value for potted plants. This big business means that this plant has been modified significantly from its wild form in order to please Christmas customers. The wild version of Euphorbia pulcherrima is a shrub that reaches heights of 8 – 10 feet! Researchers initially enlisted the help of plant growth regulators to yield a more compact plant structure suitable for indoor potted plants. Subsequently, breeding programs took advantage of some favorable genetic finds for superior poinsettia plants. Perhaps one of the most significant traits was bract retention. Instead of immediately dropping the bracts and leaves after color development as the plants are naturally inclined to do, the ‘Ruff and Ready’ cultivar retains its bracts and leaves for the length of the holiday season and is the parent stock of many varieties available today. And today, there are more than 100 varieties of poinsettias that differ in bract size, shape and color. Colors include just about every hue of the traditional red, to pink, to cream to combinations of all of the above in double tones and speckles. The Ecke family pioneered the commercial cultivation of poinsettias, and their catalogue is overflowing with examples of their breeding success stories.

More recently, USDA-ARS researchers have uncovered the biological agent responsible for generating the desirable dwarfed poinsettia plant stature without the use of expensive growth regulators. The answer was surprising- phytoplasma, an infectious agent found within some plant varieties. These bacteria are usually pathogens, but in the case of poinsettias, they actually produce a trait desirable for commercial sales. Earlier this year a similar poinsettia branching plant type was achieved by making a transgenic poinsettia expressing an Arabidopsis gene AtSHI, which alters the internal hormone balance to change plant structure. Other scientists are focusing on the diseases that attack these valuable plants. Still others are working on reducing the energy costs associated with commercial production of these plants. Poinsettias may show off their colors during the long nights of winter in the Northern Hemisphere, but they decidedly prefer warmer temperatures than those available outdoors during North American winters. This means that growers must keep the heat on inside greenhouses while the plants are getting ready for market. Energy costs have increased by 230% over the past decade, which means slimmer profit margins for poinsettia growers. Researchers have reported that some varieties can stand slightly colder temperatures while still yielding high quality plants in time for the Christmas season. They just have to start their seedlings just a little bit earlier in August. This timing adjustment in combination with the proper choice of cultivar will ultimately save energy costs for growers.

So enjoy your poinsettias for a little while longer this season. Then, when all the bracts and leaves fall off, and your family starts to ridicule your plant care-taking skills, you can impress them with your new botanical knowledge. “Well, no it isn’t my fault. That’s just what poinsettias do after they have flowered for several weeks. I’ll just prune them back and re-train them to a short day photoperiod for beautiful bract blooms next year.” Walk away as they pick their jaws up off the floor. They’ll be too stunned to ask you when was the last time you watered it (um, never?). Plus, I won’t tell anyone that you left it out overnight during a frost. Just discreetly buy another poinsettia next year, and if anyone asks how the re-blooming project went, just blame failure on your dog/cat/child/incompetent summer house-sitter and move on. If you do manage to get your plant to bloom for the next season, give yourself a gold star from me and be sure to rub it in everyone’s noses as they visit your home for the holidays. One-upping the people we love the most with picture-perfect traditions is what the season is all about anyway, right?**


*Playing Christmas trivial pursuit? What color are poinsettia flowers? Answer: Yellow. Those that answer red or pink or cream etc. can wallow in their wrongness.

**That’s sarcasm. I know it isn’t. No need for well-meaning, but nonetheless pompous comments below.

References and Links:,-save-growers.html

Capturing the Soul of Photosystem II

Something new under the sun… techniques for ‘photographing’ the PSII water splitting reaction.

Some cultures believe that taking your photograph captures part of your soul, and believers shun having their images captured to avoid any potential metaphysical rifts. If this is the case, I suppose it’s safe to say that the world is quite soulless based on the number of selfies floating around the internet these days. As it turns out scientists in my field are having a similar problem with a longstanding question regarding my favorite enzyme, Photosystem II (PSII). We need a technique for photographing PSII that doesn’t destroy its soul (catalytic center- that is).

Note, this is not the actual set up devised by Kern and colleagues

Note, this is not the actual set up devised by Kern and colleagues

PSII is a multi-subunit membrane protein complex that uses light energy to split water into protons (H+) and molecular oxygen (O2). This important reaction makes it possible for aerobic life on earth.* In order to drive this reaction, a huge redox potential is required and P680, the reaction center of PSII, is the most powerful biological oxidant (1.3 V) identified to date. Mechanistically, this is an extremely difficult reaction to do. Using four successive photons, PSII must sequentially pull four electrons from two water molecules and form an O-O bond. All of this is accomplished by the Oxygen-Evolving Complex within PSII, an inorganic cluster of four manganese atoms and one calcium atom (Mn4CaO5). This works because manganese is a transitional metal that can exist in a number of different oxidation states Mn2+, Mn3+ and Mn4+. This kind of stable redox space makes it the perfect element for holding onto the four electrons required to split water and form O2. Unraveling the mechanism by which PSII does this is one of the holy grails in our field. If we only knew how it worked, we could make artificial systems that take advantage of the mechanism for coupling light energy to electron extraction from water (translation = ‘free’ electrical energy from water).

Because of the potential applications, many scientists have been working for many years to figure out how this works. We know some things about the mechanism, but the details we need to know rely on having high resolution structural data on PSII as it is working. We’re not there yet. The currently available experimental tools fall into one of two broad categories. The first is X-ray diffraction structure data or protein crystal structures that represent a static picture of the entire complex (proteins and cofactors). The second is X-ray spectroscopy (absorption or emission). These experiments provide detailed information on the Mn4CaO5 cluster, but not really a picture- just distance constraints between atoms.

Over the past decade, photosynthesis researchers have made great strides in improving the pictures we have using these techniques, but there are some significant limitations in the data. The problem is twofold. The X-rays used to generate our beautiful high resolution (1.9 Å) crystal structure model destroys the Mn4CaO5 cluster during the process of collecting data. We know from other techniques that the energy in those X-rays reduces the Mn4CaO5 cluster to a combination of oxidation states that are not useful for water splitting. On the other hand, the other X-ray spectroscopy techniques are not damaging to the Mn4CaO5 cluster, but it doesn’t give a singular picture and multiple models can fit into the distance constraints provided by those experiments. Thus, the pictures that we get from these experiments are inaccurate or inadequate to answer the question of how PSII splits water. Plus, we would like to visually capture the process as the enzyme turns over at physiological conditions (as in not cryogenic temperatures).

Today’s post highlight’s a presentation from the Midwest Photosynthesis Meeting presented by plenary speaker Jan Kern from Lawrence Berkley National Laboratory (LBNL). He along with numerous other teams of researchers have been working to develop the techniques necessary to take snapshots of PSII as it is splitting water in a way that doesn’t destroy the enzyme. Their system will simultaneously collect data using the two different techniques (X-ray diffraction and X-ray Emission) on the same sample in such a way that the PSII Mn4CaO5 cluster isn’t destroyed. The secret to this is the use of ultra-short high-intensity X-ray pulses. It’s like having a camera that captures the image so fast you don’t even have time to blink before the flash. Also, the system is designed such that the sample can be illuminated with light for varying numbers of flashes to capture images of PSII during different steps of its catalytic cycle. This has been an enormous effort to design the proper experimental set-up and get it working. The preliminary data and proof of concept were published earlier this year in Science. Don’t get ready to start making electricity from water just yet. The system has not achieved the necessary resolution to see the fine structural changes of the Mn4CaO5 cluster as it splits water. However, Jan Kern and others at LBNL are working hard to tweak the components of their system so it does have the necessary resolution for the snapshots we need. Check out the links below for more details on how they did it.


*That’s you and me!


Simultaneous Femtosecond X-ray Spectroscopy and Diffraction of Photosystem II at Room Temperature

Room temperature femtosecond X-ray diffraction of photosystem II microcrystals

Energy-dispersive X-ray emission spectroscopy using an X-ray free-electron laser in a shot-by-shot mode

Artificial Photosynthesis

Here’s something new under the sun…

Scientists at the Joint Center for Artificial Photosynthesis (JCAP) have developed a physically and functionally coupled light-absorbing semiconductor-hydrogen-production catalyst. It just sounds cool and technical, right? What does it all mean? It means scientists are starting to build the functional skeleton necessary for solar energy production via artificial photosynthesis.

While natural photosynthesis uses sunlight to provide the vast majority of biochemical energy on Earth, artificial photosynthesis aims to streamline the energy conversion process. We’re not talking ‘biofuels’ where photosynthetic organisms use sunlight to produce biomass, which is then used as a fuel source. Artificial photosynthesis just uses the chemical and physical principles of photosynthesis, but bypasses much of the pesky biology. This entails developing materials capable of using sunlight to generate electricity or store it in the form of a fuel.

This is where the JCAP scientists come in, in particular the lab of Dr. Gary Moore. In their recent report in JACS, they were able to connect a semiconductor material that absorbs visible light to a hydrogen production catalyst. Their new material has some limitations, but it provides a proof of concept for new technologies for solar energy production. The semiconductor itself could use some optimization to take advantage of the full spectrum of visible light. Also, the modular design of the semiconductor-catalyst means that other combinations are possible as new versions become available. Scientists are working to develop catalysts that use less precious metals and more abundant elements to make this technology more economically feasible.

It’s no small feat to recreate artificial photosynthesis, but scientists at JCAP are working toward unraveling the physics behind this natural process so that it can be supercharged and applied for renewable energy purposes.

Check out this video from JCAP about artificial photosynthesis:



Stealing Photosynthesis

I’ve mentioned before that studying photosynthesis is important because scientists would ultimately like to harness that power to do useful work for ourselves- for both increased food production and biofuels for the rest of our energy demands. Well, I am sorry to report that we have lost the photosynthesis-race… to a slug. A sea slug called Elysia chlorotica.

File:Elysia chlorotica (1).jpg

Elysia chlorotica, a sea slug whose criminal activities include felony theft of algal chloroplasts
Credit: Patrick Krug Cataloging Diversity in the Sacoglossa LifeDesk
via Wikipedia and Flickr

This animal can effectively steal photosynthesis from the algae (aka pond scum) it eats. You’re probably thinking, “Yeah, that’s what I did today when I ate a salad for lunch.” Well, you’d be wrong. This sea slug is able to suck the chloroplasts right out of its favorite meal (Vaucheria litorea, a filamentous algae) like a straw and retain them within its cells instead of digesting them. This allows the slugs to become photosynthetic. I’ll let that sink in a minute while you ponder how effective your digestive system really was with that salad you ate earlier. While you do that, check out this cool youtube video of a juvenile slug dining on algae.

You don’t really think that scientists were just going to observe that phenomenon and say, “Hmm, well that’s interesting to the point of impossible” and just leave it at that. No, they had to dig deeper to find out how this really happens.

I’m sure you read yesterday’s post on chloroplasts and are well-versed in the current state of our knowledge of them. Go ahead and click the link; I’ll wait until you get back.

Caught up? Great! Let’s continue…

I mentioned that within plant (and algal) cells, chloroplasts cannot stand alone. There is an intricate messaging system between the chloroplast and the nucleus that keeps photosynthesis going. If you want to put a number on how dependent a chloroplast is on the nucleus of a cell, it would be 90%. The nuclear genome of photosynthetic organisms provides 90% of the protein components in the chloroplast. So how can the sea slug possibly have useful chloroplasts?

Your first thought may be, “Those chloroplasts are just green decoration. They aren’t really useful.” Scientists thought of that too. As it turns out, the ingested chloroplasts of Elysia chlorotica are functional enough to provide the sugars necessary to sustain the slugs for up to 10 months without another food source. Its. Entire. Life. Span.That’s pretty amazing, especially given the fact that the photosynthetic apparatus within the chloroplasts of normal photosynthetic organisms requires upkeep on the minutes timescale.

Again I ask- how can these chloroplasts be functional? Is there something different about these algal chloroplasts that make them more independent from a nucleus? Or is there something special about Elysia chlorotica cells that make this feat possible? To address these questions, scientists decided to sequence the genomes of both the algal chloroplast and the slug’s nucleus. Enough is already known from other species about what genes are universally required for photosynthesis so that scientists can simply look for these in each of the sequenced genomes. They found that the algal chloroplast is nothing special; it still lacks many of the genes required for photosynthesis typical of other chloroplast genomes and is therefor utterly dependent on a nuclear genome with these missing genes. Surprisingly, researchers found these photosynthetic genes in the nuclear genome of the sea slug. So it seems that Elysia chlorotica is not only good at stealing chloroplasts, but also the genes it needs to maintain them. Both of these things are not occurring in the same step- Elysia chlorotica cells already have these genes waiting in their nuclei. At some point in the history of this relationship, the sea slug managed to incorporate these useful genes as part of their own genetic makeup.

Having photosynthetic genes in the nuclear genome of the sea slug definitely answers some questions about this strange lifestyle, but the mystery is far from solved. These stolen chloroplasts do not divide within the Elysia chorotica cells nor are they inherited by progeny slugs. Thus, individual sea slugs must acquire all of their chloroplasts from the algae they eat. There must be an elaborate system within the digestive tract of Elysia chlorotica to recognize chloroplasts, retain them, and ingest them into their cells while discarding all other algal cell contents.

We are still far away from understanding this process enough to steal photosynthesis for ourselves or other animals we care about.* If sea slug can manage it there is hope for us, but I don’t think humans will be dropping a trophic level any time soon. After all, I still like the taste of my salad (among many, many other things) very much.


*Wouldn’t it be nice to have a photosynthetic fish or dog? You wouldn’t have to feed them as often, only give them access to sunlight. It would make vacationing away from your pets much easier.

**Here is another youtube video talking about Elysia chorotica. Note there is a typo on one slide. Plasmid should be plastid (a general term for chloroplast or related organelle). Plasmid is a completely unrelated entity in molecular biology.

*** The scientist that knows most about the secrets of Elysia chlorotica endosymbiosis is Dr. Mary Rumpho Kennedy at the Univeristy of Maine. Check out this research spotlight.

Other references:

doi: 10.1073/pnas.0804968105 PNAS November 18, 2008 vol. 105 no. 46 17867-17871

doi: 10.1242/​jeb.046540 January 15, 2011 J Exp Biol 214, 303-311.

doi: http:/​/​dx.​doi.​org/​10.​1104/​pp.​123.​1.​29 Plant Physiology May 2000 vol. 123 no. 1 29-38

By the numbers: Energy from the Sun

It starts with the sun… Photosynthetic organisms use sunlight as a power source. Therefore, the rest of us that have to eat plants (or the other delicious organisms that have to eat photosynthetic organisms) are also indebted to the sun for energy. How much are we talking about? Let’s talk numbers in the first installment of ‘By the numbers’:

The average amount of solar energy hitting the earth’s surface is 4.2 kilowatt-hours of energy per square meter for a 24 hour day. Of course this will vary significantly depending on the day of the year and whether you are in a place like Forks, WA or Tuscon, AZ. Not impressed? Let’s think of it another way…

One acre is ~4046 square meters. This gives you 16,993 kWh of incident energy per day per acre. Ok, that’s bigger, but probably still out of context for you.

Think about this: a gallon of gasoline has an energy content of 36.6 kWh. So the average acre receives the amount of energy from the sun equivalent to ~464 gallons of gasoline. Each. Day. Are you surprised yet?

How about this: The total U.S. Energy consumption for the year 2011 for all sources (coal, oil, electricity, renewable whatever)* was 97.301 Quadrillion BTU = 2.85 x1013 kWh. From the numbers above, the average acre on earth will give you 6.2 x106 kWh per year. If we could harness all of that energy, then we would need 4.6 x106 acres or 7187.5 square miles to supply all of our current domestic energy needs. If these numbers are still making your head spin, it corresponds to a land area equivalent to about 13.8% of the state of Louisiana. It’s only 6.3% of the land area of Arizona, the state with the highest values of incident solar energy, according to estimates made by the National Renewable Energy Lab (NREL) in Golden, Colorado. See map below.


Of course, in these calculations we are just talking about potential- in this case, a nearly upper limit for possible energy available with 100% conversion efficiency. At every step from incident photon to electricity useful for human consumption, there are losses. If you make some assumptions, like 15% conversion efficiency, the amount of land area required to replace the annual U.S. energy consumption is ~48000 square miles, just less than half the size of Arizona. This number may be less impressive, but it is still in the realm of ‘possible.’

With such an abundance of energy, it’s no wonder scientists are trying to tap solar for our energy needs. That’s why it’s important to study how photosynthetic organisms capture and convert this energy- not solely for the purpose of making ‘super plants’ but also using engineering principles from biology to create economical and self-sustaining photovoltaic cells.

Interactive bonus: NREL has an on-line tool called In My Backyard that allows you to estimate how much energy you can generate by installing various-sized solar panels at your home (or business) address. It also estimates installation cost and how long it will take to recover your costs.


*Since we are speaking of numbers today, you may be amazed at the sorts of things that scientists somewhere are counting. If you ever wanted to know numbers related to energy, go to the U.S. Energy Information Administration.