Category Archives: future challenge

More Forest Numbers and Tree-Planting Drones

Here’s a new idea under the sun… tree-planting drones.

Take a minute and think about all of the forest products you use in a day. I’m sitting on one right now as is my laptop. Anyone who’s bought school supplies in the last weeks has also consumed a fair amount. As an avid list-maker, I use my fair share of small pieces of paper for reminders and tasks to be done. Of course, let’s not forget the oxygen. The U.S. Forest Service estimates that forest products account for 4.5% of the total U.S. manufacturing gross domestic product at $190 billion in products annually and employing >900,000 people. There’s little room for doubt, forests are valuable both as they stand and as they fall.

I’ve mentioned before that numbers are important. In this context, numbers about forests can be extremely valuable. New research in Nature this week gives a new estimate of our global tree density. The good news… The earth has nearly an order of magnitude more trees than previously estimated by satellite imagery. The research team puts the total number of trees on the planet at 3.04 trillion. That’s more than 400 trees per person. To you, these numbers are likely just interesting statistics to impress your friends, but to scientists, conservationists and the forestry industry the new estimates of tree density are important for guiding management policies.

The new estimate is based on more than 400,000 ‘ground-sourced measurements of tree density from every continent except Antarctica.’ Translation: A lot of man-hours were spent by humans in a forest collecting tree density data. Of course, the team wasn’t able to count each and every tree, but this is more accurate data than estimating tree numbers from space. Check out the video below for a great data visualization of the world’s forests based on this new research.

If you were paying attention, forest numbers are not static. For various reasons around the globe forests are declining. Current estimates give a net loss of 10 billion trees a year. Some of this loss is due to forest fires, but for decades the forestry industry has become increasingly mechanized to efficiently harvest trees for all of those useful forest products. On the other side of the equation, replanting new trees has not experienced the same industrialization and relies heavily on meticulous man hours and dirty hands. The company BioCarbon Engineering seeks to change this and offers a new scalable model for planting trees using drones. Yes, drones for a noble purpose. The drones are engineered to shoot bullets wrapped in a biodegradable casing and containing soil with pre-germinated seeds into the ground. This could be used for replanting after forest fires or in other areas where forests need help with recovery.

From BioCarbon Engineering

They estimate that they can scale up to 1 billion trees per year. It greatly decreases the amount of human hours involved compared to hand-planting. It’s also more efficient relative to mass seeding because the seeds are pre-germinated, which will eliminate the loss due to bad seeds. The numbers are still not yet in the trees’ favor, but closing the gap with deforestation is a step in the right direction and the Lorax would be proud.

Johnna

*Of course, BioCarbon Engineering could always enter into a relationship with that BIOS Urn company that uses your cremated ashes as the germination medium for tree seeds. Then you and your loved ones could have your ashes with tree seedlings shot almost anywhere to make a stand of trees somewhere in the wilderness rather than just one tree at a time with a single urn. But as I’ve mentioned before, that’s not exactly how photosynthesis and the carbon cycle works.

//The blog has been dark for a record length of time. Only for lack of time and not material. Regularly scheduled posts coming soon.

References and Links:

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14967.html

http://www.nature.com/news/global-count-reaches-3-trillion-trees-1.18287

For more on the tree-counting research, check out this post over at The Quiet Branches blog.

http://www.biocarbonengineering.com/

http://www.biocarbonengineering.com/blog/deforestation

http://www.biocarbonengineering.com/blog/deforestation-data

http://www.biocarbonengineering.com/blog/what-is-the-social-value-of-a-tree

http://www.msnbc.com/greenhouse/watch/using-drones-to-improve-reforestation-445645891970

http://www.fao.org/docrep/014/am859e/am859e08.pdf

http://www.fs.fed.us/

The Dangerous Double Life of a Distinctive Diazotroph

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For many people around the world, tonight is one of the most anticipated nights of the year. In that spirit, here’s some new science, not under the sun, but under the moonlight and starlight. New research from Wegener, Nagarajan and Pakrasi* describe something new about the Photosystem II D1 protein, an unexpected source that photosynthesis researchers had long written off as conquered or fully explained.

Why would we care about photosynthesis at night anyway? It all comes down to the distinctive lifestyle of the cyanobacterium Cyanothece, which belongs to an interesting class called unicellular diazotrophs (word of the day). Like all cyanobacteria, they perform oxygenic photosynthesis but they have the bonus biochemical ability of nitrogen-fixation.

Nitrogen-fixers are capable of pulling nitrogen gas (N₂) out of the air and turning it into ammonia which the cells can use as a nitrogen source for important molecules like protein and DNA. Other microbes can perform nitrogen-fixation, and you may remember them as the root nodule symbionts of legumes. If you’re not a nitrogen-fixer, you have to rely on ammonia or other nitrate compounds present in the soil, sea or your diet (depending on what kind of organism you are) to make the required nitrogenous biomolecules. Since the Earth’s atmosphere is 78% N₂, you don’t have to be great at math to figure out that acquiring the ability to tap into the atmospheric nitrogen source advances your species in the game of life a considerable number of squares.

What does this have to do with photosynthesis? Why don’t more plants and cyanobacteria get in on this nitrogen-fixation biochemistry? There’s a critical fatal flaw in the photosynthesis/nitrogen-fixation biochemical tango. Nitrogenase, the enzyme responsible for the nitrogen-fixation reaction is hopelessly and irreversibly killed by oxygen. Oxygen destroys the protein enzyme that’s already been made and tells the genome not to even bother wasting energy trying to make it new. If you’ve been paying attention to the blog, oxygenic photosynthesizers like cyanobacteria and plants make oxygen via their PSII enzyme every time light shines on them. So for nonphotosynthetic soil bacteria and other microbes, it’s not a big deal to avoid oxygen and go anaerobic to fix nitrogen. Cyanobacteria, however, must lead dangerous double lives to combine these two opposing biochemical processes.

Anabeana spherica via Wikimedia Commons The more round cell in the center of the string is the nitrogen-fixing heterocyst.

Some diazotrophic cyanobacteria solve this problem by separating these two processes in space. Species like Anabeana can go through a special type of development where the cells divide themselves, but incompletely to form a connected network like beads on a string. Every tenth cell (heterocyst) gets an extra layer of cell wall, destroys its photosynthetic machinery, and commits itself to a life of nitrogen-fixation. These cells share their fixed nitrogen compounds with their neighbors, which in turn share their fixed-carbon from photosynthesis. This is a fascinating process still hasn’t given up all of its secrets and remains an active area of research.

Cyanothece 51142 by Michelle Liberton, Pakrasi lab

Cyanothece, on the other hand, is a more ruggedly individualistic species that manages to perform both oxygenic photosynthesis and nitrogen-fixation within a single cell. It accomplishes this through a carefully controlled circadian rhythm. During the day, oxygenic photosynthesis occurs. During the night, nitrogen-fixation occurs. It sounds so simple, yet this elegance is far from easy. This is a true circadian process, in that, while some cues are definitely derived from light signals, the cells also have a strong internal clock that keeps the time of day and controls what biochemical machinery is active. Thus, near the hour of dawn and dusk, the cells are actively preparing for the metabolism to come. Also, if you were to train a culture of these cells under a certain day/night cycle for several days then switch them to continuous light, they would still maintain their circadian biochemical cycle for several days after the switch.

One issue that has puzzled researchers for some time is that the photosynthetic machinery, like PSII, is actively shut down at night. It’s not just that it’s dark, so there won’t be any photosynthetic oxygen production. Apparently, that’s not good enough. The cells actively shut it down. When researchers take culture samples of these cells during their dark period and shine light on them to check photosynthetic capability, there is no signal. Sure, there’s probably little chance any significant photosynthesis is occurring at night, but Cyanothece isn’t taking any chances. For these cells, no moonlight, floodlights from passing ships, comets, or even the blessed Eastern Star is going to interfere with their nocturnal nitrogen fixation.

Shutting down photosynthesis is no small feat. Again, if you’ve been paying attention to the blog, you will note that I’ve ranted on numerous occasions about how complex PSII is and how difficult it is to assemble and reassemble from its individual parts. As far as energetics are concerned, it would be a losing battle for Cyanothece to completely disassemble its PSII at dusk only to resynthesize it again the next morning. I don’t care how hard-up it is for a nitrogen source. As it turns out, Cyanothece and other unicellular diazotrophic cyanobacteria solve this problem in a more graceful way, for which Wegener et al have provided new experimental evidence.

Cyanothece, like all other oxygenic photosynthesizers, contains multiple copies of the psbA gene encoding the D1 protein, which is a core subunit of PSII and critical for function. Since the advent of the genomic era, the genomes of numerous photosynthetic organisms have been sequenced revealing these multiple psbA genes, most of which have little or no protein sequence differences. These subtle changes have been linked to cells’ ability to fine-tune photosynthesis under certain conditions. However, Cyanothece and its cousins have a psbA gene copy that is particularly different- psbA4. If one were to take all of the site-directed mutants that photosynthesis researchers made to sort out PSII function over the last few decades since molecular biology techniques were available and threw them altogether into a single mutant gene, you would get psbA4. If PSII contained the D1 protein encoded by psbA4, there would be no C-terminal processing and no active site for water-splitting and oxygen production.

Why would any self-respecting photosynthetic organism retain such an utterly non-functional PSII subunit? The answer is because it does serve a critical function in the daily cycle of Cyanothece, just not during the day. The D1 protein encoded by the psbA4 gene, called a sentinel D1 protein (sD1), is made only for the night, when it does the only thing it still can do- fit right in the center of the PSII complex and prevent PSII function of any kind. There’s no chance of any oxygen production while sentinel D1 is on duty, but the cells can maintain most of the other PSII components in a stable complex (meaning they don’t have to be degraded and made fresh every morning). Then, Cyanothece can turn photosynthesis back on in the morning by replacing a single protein in its PSII complexes. The report by Wegener et al gives the first biochemical characterization of PSII complexes containing a sentinel D1 protein, providing evidence that this strategy works for controlling PSII oxygen production.

Performing oxygenic photosynthesis and nitrogen-fixation within the same cell is biochemically problematic, but the sentinel D1 protein appears to be the secret weapon for this dangerous double life. Through this strategy oxygenic photosynthesis and nitrogen fixation are “Always together, eternally apart.”** Many questions remain regarding the regulation of the transition from functional D1 to sentinel D1 at dusk and the reverse replacement at dawn. There are still outstanding questions regarding the D1 turnover event for any PSII in any photosynthetic organism, so it’s not at all clear what parts of this process Cyanothece uses or whether new factors are involved. Obviously, there must also be some sophisticated regulation to prevent the synthesis of sentinel D1 during the day.

While this work focuses on an organism you’ve never heard of, it has some interesting biotech implications for the future. As I mentioned, being able to both fix CO₂ through photosynthesis and N₂ through nitrogenase puts you at a significant metabolic advantage. And no, I don’t mean you. Remember, we’ve been through this- people are not photosynthetic. It would be great if one day we could engineer certain crop plants to combine these traits. Legumes already have this trick covered through symbiosis, but many other staple crops require tons of nitrogen fertilizer. If researchers could unlock the secrets of Cyanothece’s double life and translate it to plants, then it may be possible to engineer versions of crop plants that don’t require so much nitrogen fertilizer. Thus, one night in the future, engineered crop plants may be fixing nitrogen thanks to the addition of a variant gene they already had.

Johnna

*I know I’ve posted frequently about Pakrasi lab (my thesis lab) research, but this topic was just developing as I was leaving the lab and it’s too cool to pass up.

**Bonus points to you if you get the movie reference.

References and Links:

http://www.jbc.org/content/early/2014/12/18/jbc.M114.604124.full.pdf+html?sid=8f38f7c6-96c1-4085-bbb0-efc6ca425624

Dangerous Photosynthesizers

Plant Cold Tolerance

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Kicking off the scientific section of the Frozen series…

Some plants can endure the cold,

Even freezing temps surviving

Gene transcription levels change ten-fold

But the important thing’s the timing.

CBFs start the response pathway,

Activating others to join the fray,

This works when there’s not a sudden freeze one day

It’s bad enough to lose a limb,

But plants must protect their meristems!

For those readers who are not compliant with our rodent overlord and have not seen the movie Frozen, here is a link to the Youtube clip with corresponding song.

Ice in biological systems is just as bad for plants as it was for poor Anna in Frozen. The sharp edges of ice crystals tend to rip biological membranes to shreds in ways they can no longer function or be repaired. In freezing temperatures, crucial biomolecules slowly lose mobility and grind to a halt. Both of these consequences violate central tenets of living systems. Cells need intact membranes to maintain the integrity of the ion gradients responsible for fueling bioenergetics, and all biochemical reactions depend on small motions in all molecules. Thus, all living things want to keep their cytoplasm from turning into snowflakes. So, how do plants deal with freezing temperatures? It’s not like they can just go inside their castles next to a warm fire. And for the record, acts of true love aren’t very helpful either. Today’s post explores how plants adapt to falling temperatures.

Temperature is an important factor governing the molecular details of plants’ lives. The activities of the enzymes that carry out routine metabolism are affected by the ambient temperature. The fluidity of plants’ numerous important membrane systems is also influenced by temperature. Consequently, plants must make significant internal adjustments to adapt to colder temperatures. Even though the leaves of your cold-hardy plants may not look any different in summer compared to winter, there are many molecular-level changes with respect to the types of proteins and membrane lipids that the cells contain. These changes require an energy commitment that makes it wasteful or impractical for plants to always have cold-tolerance turned on, so they have an elaborate system for inducing cold-tolerance.

Very few plant species would be able to survive Elsa’s magical wrath, which turned a normal summer day into deep winter. For the most optimal cold-survival, plants need exposure to lengths of cold-but-not-freezing temperatures to trigger internal pathways to get ready for freezing temperatures. This generally works well for plants on Earth* since the cooling temperatures of autumn precede the first snowfalls of winter. During this time, plants are acclimating at the molecular level for the onslaught of months of freezing temperatures. It shouldn’t be that surprising that cold-acclimation is linked to plants’ circadian clock and timekeeping mechanisms for day-length since these are also tightly connected with seasonal temperature changes.

Plant scientists have been working out the details of just what plant cells are doing during this acclimation time. One of the first things triggered by colder temperatures is the gene expression of the CBFs (C-repeat Binding Factors). These CBF regulatory proteins then activate other genes responsible for the grunt work of protecting cells from freezing temperatures. This layered response gives the plants more ways to regulate the biochemical changes as well as simplifies the initial activation of the pathway. The exact functions of the structural proteins which confer freezing-tolerance are still under investigation, but they have roles like stabilizing membranes under freezing temperatures or producing cryoprotectant molecules like sugars. Plants also change expression of genes controlling development so that growth is controlled during dangerously cold seasons. Teasing out the underlying mechanisms plants use to protect themselves from freezing temperatures is an active area of research in plant science.

Frozen plants by rockmylife via DeviantArt

Researchers are also interested in how cold-acclimation systems differ between plant species in order to gain insights as to why plant species have such differences in cold-tolerance (say, citrus vs. pine). Is it because the less cold-tolerant species don’t have some of the structural proteins necessary to protect cells during freezing temperatures? Or is it because the cold-sensitive species lack or have less responsive regulatory proteins for acclimation? Can the genes responsible for cold-acclimation be transferred to cold-sensitive plants to confer better freezing tolerance? Plant scientists are diligently working to find answers for these questions.

Hey, I’m sure there is some agribusiness that would love to open the market for citrus crops up to farmers in Minnesota,**but I think more modest adjustments in hardiness for certain agriculturally important crops are what they are aiming for. Even so, you may be wondering at this point, “Haven’t scientists been wailing for years about how the climate is getting warmer not colder? Why bother with cold-tolerance now? Can’t we just wait it out?” I’d say, “Sure, when there is beachfront property in Arkansas, go ahead and grow grapefruit there.” However, the story is a little more complicated than that, and it’s also important to mention that freezing-tolerance isn’t all about the thermometer. A big part of dealing with freezing temperatures means coping with less available liquid water. In studying freezing-tolerance, scientists have also uncovered connections with drought tolerance. That’s right, the same systems that kick in to handle frost intersect and merge with those conferring drought-tolerance. Thus, the more we know about freezing tolerance, the more we learn about drought tolerance. I think we can all agree that finding more ways to increase drought tolerance in plants is useful in places other than fairytales.

Johnna

* I can only hypothesize that the flora of fairytale worlds has a much quicker cold-tolerance induction response or that there is other magic to mitigate sudden frost damage.

**Hey, maybe there’s an idea for finally getting rid of that awful citrus greening that’s decimating Florida’s citrus groves. I have a feeling the insect vector that carries the disease will have a difficult time surviving winters in the northern Midwest.

References and Links:

http://www.metrolyrics.com/frozen-heart-lyrics-soundtrack.html#ixzz37C0QG3RL

http://disney.wikia.com/wiki/Frozen_Heart

http://www.prl.msu.edu/faculty/thomashow_michael

http://www.annualreviews.org/doi/abs/10.1146/annurev.arplant.50.1.571

http://www.plantphysiol.org/content/154/2/571.full

http://www.sciencemag.org/content/280/5360/104.short

http://www.sciencedaily.com/releases/2010/08/100826141213.htm

http://www.plantstress.com/articles/up_cold_files/Understanding%20cold%20hardiness%202013.pdf

http://www.oardc.ohio-state.edu/stockingerlab/t08_pageview/Research.htm

http://www.mdpi.com/1422-0067/14/6/11527

http://journal.frontiersin.org/Journal/10.3389/fpls.2013.00167/full

The Countdown Starts…

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Four…Three…Two…One…

Earth below us, greening, glowing, cycling carbon, photosynthesis!

Red fluorescence tells the story, satellites can measure, measure it!

Wait, those aren’t the lyrics to Major Tom Coming Home. Not quite, but more appropriate for the upcoming OCO-2 NASA mission scheduled to launch in less than 24 hours! That stands for Orbiting Carbon Observatory-2, a satellite equipped with instruments to measure carbon dioxide in the Earth’s atmosphere. What does photosynthesis have to do with it? A lot. No matter how the carbon dioxide finds its way into the atmosphere- vehicle emissions, thawing tundra, the panting of my dogs in the Louisiana summer heat- photosynthetic organisms are its ticket out of the atmosphere and back into the solid state. The OCO-2 satellite will be collecting spectral data for direct measurements of atmospheric carbon dioxide as well as sun-induced fluorescence to monitor photosynthesis on a global scale.

Watching in a trance, the crew is certain, Nothing left to chance, all is working…

Now that you know what the OCO stands for, you might be wondering about the 2. Of course there was a ‘1’. Starting with 2 would just drive people like the scientists and engineers at NASA crazy. The OCO-1 launched in 2009 with a similar mission to collect carbon dioxide concentration data, but it failed to launch properly and crashed into the ocean before making it anywhere close to its orbit. Sigh. After I’m sure a lot of this happened, the scientists and engineers got back to work to make the replacement mission even better. You can bet that everything has been quadruple checked this time.*

Starting to collect requested data, What will it effect when all is done?

Remember when I told you how nifty it was that satellites were measuring photosynthesis from space while I was making the same measurements in the lab? Well, it’s not just a scientific novelty being measured because it can be. Chlorophyll fluorescence on a global scale provides critical information for accurate models of primary productivity and global carbon cycles. A recent report in PNAS showed that sun-induced fluorescence data could be used to model gross primary productivity.** The authors found that estimates based on chlorophyll fluorescence data were much higher for major agricultural areas like the U.S. Corn Belt than models using other measures. These findings mean our current models may be underestimating how much modern agriculture and other managed areas contribute to the Earth’s carbon cycle. That report focuses on land photosynthesis, but I hope that the satellites will be collecting the chlorophyll fluorescence signal from both the land and the oceans. Let’s not forget that the photosynthetic bacteria in the ocean account for about half of the Earth’s primary productivity. I’m sure they have it covered since they have long been interested in mapping ocean color.

Check out this video for more on the OCO-2 mission.

There’s a lot of politics behind the amounts of carbon dioxide in the atmosphere, what’s causing them to creep increasingly higher and what that means for global climate patterns. Collecting accurate data on how much carbon dioxide is released into the atmosphere as well as the capacity of photosynthetic organisms to reclaim that carbon dioxide will greatly aid in global climate models that will be used to direct policy.

OCO-2 Satellite, Oh how I wonder what you will see for us. Safe journey and Godspeed.

UPDATE 07/01/14: For those of you that didn’t set your alarms early to watch the launch…

The computer has the evidence, need to abort, the countdown stops…

At T-46 seconds to be precise. There was a problem with the pad’s water system during the launch sequence that caused the mission to be aborted today. The satellite and rocket are all still ready to go, but NASA’s scientists and engineers need to figure out the source of the problem and a new launch date for the OCO-2 mission. Check here for the latest. And follow OCO-2 on Twitter!

UPDATE: 07/02/14

The OCO-2 do-over launch was successful today. Don’t just take my word for it, listen to OCO-2:

I’m alive! Congratulations to the entire OCO-2 team! #OCO2 #nasasocial #EarthRightNow

— NASA OCO-2 (@IamOCO2) July 2, 2014

Johnna

*If a launch failure happens again, I’m willing to start entertaining conspiracy theories.

**It should be noted that chlorophyll fluorescence has long been a standard technique in the laboratory for analyzing photosynthetic efficiency. Scientists have even scaled it up for field analysis. The real breakthrough in recent years has been observing this faint signal from plants via satellite using only the incident natural sunlight (not artificially bright light subjected to plants in a very controlled way).

References and Links:

http://www.metrolyrics.com/major-tom-coming-home-lyrics-peter-schilling.html

http://www.popsci.com/technology/article/2010-06/nasas-orbiting-carbon-observatory-replacement-mission-launch-2013

http://en.wikipedia.org/wiki/Orbiting_Carbon_Observatory

http://www.spaceflightnow.com/taurus/oco/failure.html

http://www.nasa.gov/pdf/401097main_2009-05-12-Science_Contributions_from_an_OCO_Reflight_20090916.pdf

http://www.nasa.gov/missions/schedule/index.html#.U6NO-rFnCzg

http://www.nasa.gov/mission_pages/oco/news/oco-20090717.html

http://www.nasa.gov/mission_pages/oco/main/index.html

http://oco.jpl.nasa.gov/

http://remotesensing.spiedigitallibrary.org/article.aspx?articleid=708091

http://onlinelibrary.wiley.com/doi/10.1029/2006JD007375/pdf

http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/39211/1/03-0563.pdf

http://science.nasa.gov/missions/oco-2/

http://www.jpl.nasa.gov/news/news.php?CFID=73ff2bb6-0242-4266-8911-25bbb8b91e46&CFTOKEN=0&release=2014-141&utm_source=iContact&utm_medium=email&utm_campaign=NASAJPL&utm_content=earth20140505

http://www.sciencemag.org/content/344/6189/1211.full

Carnations: The Blanket of Champions

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Today is the running of the Belmont Stakes, the third jewel in thoroughbred horseracing’s Triple Crown. This mile and a half race is known as the ‘Test of Champions,’ sorting out the speedy flashes in the pan from those that can race with endurance. Like the other two jewels of the Triple Crown, the Belmont Stakes has its own floral tradition.

Blanket of white carnations on the Belmont Stakes winner Credit: Craiglduncan via Wikimedia commons

White Carnation Credit: Dysepsion via Wikimedia Commons

White carnations are the prize of the victor. Wow. Carnations. Dianthus caryophyllus. The ubiquitous ruffled flower used as filler in almost every floral arrangement. Personally, I am not a fan of these blooms and feel they should be relegated to their place in history as boutonnieres of the 1970s. Yes, I said it. I’m sure I’m in the minority view since carnations are economically important worldwide in the floral trade. Still, you’d think the Belmont and potential Triple Crown champion would be adorned in something more lavish like orchids or plumerias to go along with the silver bowl made by Tiffany and Co. Yet it is the fundamental characteristic of the carnation as a cut flower- endurance- that deems it the most fitting ornament for the winner. Their soft colors and delicate ruffled petals belie their stamina in the vase compared to other blooms, and this is why carnations have been a mainstay of floral arrangements for centuries to the point of being unremarkable, tacky even. Analogous hardiness and perseverance in the racehorses is critical for success in the Belmont and celebrated in the form of the carnation flower.

Carnation line drawing Credit: Pearson Scott Foresman via Wikimedia Commons

As in racehorse breeding, ornamental plant breeders are seeking to combine the desirable traits of flash and fortitude. I’ve mentioned in several other posts about the genetics behind new color patterns and flower forms, but the ultimate champions in the floral industry must have stamina in the vase. This isn’t something that plants have a natural tendency to do. The purpose of flowers is to provide a desirable visual attractant to pollinators; usually insects- plants could really care less about what people think of them.* Once pollination occurs, the flower’s job is done and there’s no need for the plant to invest the energy into maintaining firm colorful petals. Thus, after pollination the flowers begin the program of senescence, in which certain cells and tissues die and fall off of the plant. Plant scientists and horticulturists are working to understand the factors involved in order to find ways to short-circuit the process and keep cut flowers alive longer in our arrangements. The complex biochemical pathways that control floral senescence make this task about as difficult as breeding a Triple Crown winner.**

White carnations are also said to represent love and luck. Sure there is a lot of love poured into the Belmont Stakes contenders. No one will discount the chance events that aided the campaigns of the three-year-old horses up to this point, but there is a great amount of dedication, training and hard work by both species contributing to success on the racetrack.

White carnation Credit: Takkk via Wikimedia Commons

“I believe luck is a concept invented by the weak to explain their failures.” –Ron Swanson

Whatever the factors contributing to the victory, the winning horse will get a blanket of white carnations painstakingly assembled by the official florist of the New York Racing Association, Tony Green and his team the day of the race. The thousands of the best-looking carnation flowers were chosen earlier this week and have been soaking in water for the past 48 hours to ensure maximum plumpness. 700 of them will be meticulously glued onto the green fabric to form the blanket for today’s winner. That’s not the only blanket that will be made today. Florists will actually be assembling another blanket to go onto the statue of Secretariat, track and world-record holder for one and half miles on dirt. Actually, there will probably even be a third carnation blanket because Secretariat’s first carnation blanket will likely wilt in the humidity before the end of the day and need to be replaced. Not even carnations have the endurance to withstand those conditions.

Johnna

*Michael Pollan might disagree. Plant-human interactions have changed quite a bit and once humans become artificial plant pollinators and propagators, the selective pressure changes tremendously.

**But remember there are some advantages of plants vs. thoroughbreds when it comes to manipulating genomes. Last I checked, transgenic technology is not allowed nor is it available for thoroughbreds.

References and Links:

http://en.wikipedia.org/wiki/Belmont_Stakes

http://www.belmontstakes.com/

http://www.belmontstakes.com/history/carnationblanket.aspx

http://www.belmont-stakes.info/carnations.php

http://www.thewire.com/national/2014/06/your-guide-to-the-belmont-stakes/372364/

http://www.americasbestracing.net/en/the-latest/abrv/2014/6/5/exploring-the-belmonts-blanket-of-carnations/

http://gardeningsolutions.ifas.ufl.edu/giam/plants_and_grasses/flowering_plants/carnations.html

http://en.wikipedia.org/wiki/Dianthus_caryophyllus

http://web.extension.illinois.edu/cfiv/homeowners/090219.html

http://www.proflowers.com/blog/history-and-meaning-of-carnations

http://www.oardc.ohio-state.edu/joneslab/manuscript_PDF/Woodson_Jones_ACTA.pdf

Adamantium, for plants!

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Researchers have basically created the plant equivalent of Wolverine

One of the goals of photosynthesis research is to improve plants’ productivity to a level adequate for human food and energy needs. As of now, plants are currently doing a good enough job to reproduce themselves and mostly sustain our biosphere, but we would still like to kick this up a notch. Scientists are using a variety of tools to tackle this problem. The most notable is using genetics- either by breeding new varieties or genetically engineering new traits by manipulating specific genes sometimes between different organisms. Today’s post features another type of engineering to improve plants ability to photosynthesize- nanotechnology.

Researchers at MIT report that plant chloroplasts can be infused with carbon nanotubes to impart increased photosynthetic capacity (as much as 49% greater than unaltered chloroplasts and 30% in whole plants). Much like the X-Men character Wolverine was infused with the metal alloy adamantium to render his skeleton indestructible and give him those awesome retractable claws, plant chloroplasts can be infused with special materials to give them what amounts to photosynthetic superpowers. No, they didn’t use adamantium. The material used in their study was carbon nanotubes fused to cerium oxide nanoparticles aka nanoceria.*

You may be wondering to yourself, “What exactly are photosynthetic superpowers?”**

The nanoceria are able to absorb infrared light, which no native plant pigments can do. Plant pigments like chlorophylls and carotenoids do a good job of covering the visible light spectrum, but this is only half of the incident solar energy beaming down on them all day. The researchers in this study conclude that the boost in photosynthetic capacity is in part due to the fact that the nanotubes absorb light energy beyond the visible range and can then transfer this energy to the photosynthetic machinery. In this way, the nanotubes are acting like an antenna- a giant antenna that doesn’t just boost the signals you’re already getting, but allows access to a whole set of new premium channels.

The nanotubes have a couple of other advantageous side effects as well. The cerium oxide nanoparticles are quite effective radical oxygen species (ROS) scavengers. Remember when I told you photosynthetic organisms have a complicated relationship with light? They need enough of it to live, but too much can be extremely damaging. This is why blasting plants with bright light at all times isn’t necessarily the best way of improving their growth and productivity. Likewise, improving their ability to capture light can also be dangerous. This is all due to the fact that overloading the photosynthetic circuitry with too many electrons can start to generate ROS which in turn irreversibly damage proteins, pigments and DNA they encounter. Since the nanoceria are quite good at scavenging or capturing and inactivating ROS, they also boost photosynthesis by helping out plants’ innate systems for dealing with this problem. Again, like Wolverine, plants have some level of ‘healing powers’ when it comes to dealing with light, but the nanotubes help kick it up a notch. Wolverine’s adamantium doesn’t really help with his healing powers, but coating his skeleton with it means it doesn’t get broken as easily and he doesn’t have to use his healing powers to mend broken bones. In the same way, the nanoceria prevent some damage before it happens so the plants don’t have to waste their resources on repairing damage caused by ROS.

In true superhero style, the nanotube-infused chloroplasts’ powers don’t stop there. They also confer the ability to detect certain chemicals in the environment. Yes, just like Wolverine has heightened senses (if he twitches is nose, he’s knows you’re there!), chloroplasts containing nanotubes do too. Different types of nanoparticles have been developed to detect toxins and pollutants like nitric oxide, sarin gas, and TNT. Integrating this technology into a photosynthetic organism may allow plants to become stealthy biodetectors of these chemicals. No longer would they be merely scenery, but solar-powered secret agents (green-ops?) with skills no training could ever provide.***

These super powers may not be indestructible retractable claws, but it’s a good start down the path to lots of useful applications.

Conclusion: Plants infused with nanoceria definitely qualify as super photosynthesizers, but we still have some work to do to put this into useful practice beyond the lab.

How do nanoparticles and enhanced photosynthesis affect plants over their entire lifespan vs. short experiments in the lab? Does this kind of boost in the light reactions translate into an increase in biomass? Sure, the light reactions could always use some help when sunlight is less than its brightest, but the real rate-limiting pathway is the dark reactions. (I’m looking at you Rubisco!).

How can this technology be translated into field agriculture to boost productivity of crops? Is it worth it? It’s not like you can propagate the nanotubes biologically, but who knows, maybe in the future tractors will be outfitted with attachments to infuse or spray seedlings with nanoparticles. In terms of calculating potential for improving plant productivity, photosynthetic energy conversion remains a variable in the equation that has yet to be thoroughly tapped when it comes to improving crop plants. Using carbon nanotubes to extend the spectrum of useful light into the infrared would definitely help plants breakthrough some yield ceilings we are seeing.

How can we turn our scenery into useful biosensors for pollutants? What kinds of chemicals can they detect and how can that be cheaply and easily measured? Sure, everyone and their grandma has a satellite and a drone these days, but are we really going to have to laser scan our environment every hour? How about a nice color change or wi-fi signal that NORAD can detect?

Speaking of wi-fi, why can’t we engineer plants with nanotechnology that allows them to have other superpowers, like transmitting wi-fi signals? Solar-powered free internet anywhere! Finally, getting plants to release something useful besides oxygen****, and it would go a long way to keep me from going over my monthly data plan limits.

These are all questions and exciting possibilities that will keep photosynthesis researchers like the Strano lab busy for years to come.

Johnna

*IMHO, ‘nanoceria’ is itself a name worthy of comic book lore. Maybe DC Comics can do a series where Swamp Thing is infused with nanoceria boosting his plant-like powers.

** You must be new here. Welcome.

***K-9 units may be relegated to history. SWAT, move over for SWNTs. (You’ll get it if you read the paper).

****It’s important to me that you catch the sarcasm in that phrase. If you’ve been breathing today, thank a photosynthetic organism.

References and Links:

http://phys.org/news/2014-03-bionic-synthetic-nanoparticles-photosynthetic.html

(paywall) http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat3890.html

http://www.scientificamerican.com/article/bionic-plants-offer-superpowered-photosynthesis/

The Twelve Days of Christmas Plants: Oranges

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

If you have made any New Year’s resolutions to be healthier in 2014, hopefully today’s topic will inspire you. Citrus fruits of all kinds are bountiful in winter and have worked themselves into our Christmas traditions. Many receive an orange in the bottom of their stocking for Christmas. There’s even a tear-jerker short story about The Christmas Orange. The Orange Bowl will be played tonight.* Thankfully, oranges and other citrus products are no longer extravagant seasonal luxuries. However, this time of year they are at their peak if you live where they can be locally grown. If you are looking for healthy snacks to atone for your holiday dietary indiscretions, citrus is a great place to start. Here’s more on the science behind the citrus.

Orange blossom and oranges. Taken by Ellen Levy Finch (en:User:Elf) March 23, 2004. Originally uploaded on English Wikipedia.

First, let’s start with some numbers:

Citrus production is a $3 billion market in the United States. That’s more than 11 million tons of citrus. Not surprisingly, Florida is the leading citrus-producing state (63% of US production totals) followed by California (34%), Texas and Arizona (3% combined). Despite our demand for this healthy fruit and citrus juice products, the market is not on the rise. Florida’s yields in both production and value have been losing ground in recent years (down 9% between the 2011/12 and 2012/13 seasons). Keep reading for more on the reason why.

Of course, it’s not just Christmas Oranges. Citrus fruits include lemons, limes, grapefruit, tangerines, pomelos and a slew of other varieties and hybrids. We eat these healthy whole foods because they are a good source of Vitamin C, but they don’t have a monopoly on this nutrient. Check out this list.** Citrus derives its name from the high content of citric acid, the pucker-inducing chemical that gives the fleshy fruit their distinctive sour taste. Of course, the distinctive smell of citrus comes from volatile chemicals stored in special glands in the peel. The main ingredient is a chemical called limonene. And what about their signature color? All immature citrus fruit goes through an immature green phase. There are chloroplasts within the cells of the peel layer of the fruit that supply energy to the developing tissue. At some point in the developmental program of citrus fruit ripening (triggered by colder temperatures), these chloroplasts undergo a major metamorphosis. They completely rearrange their membrane structure, shut down their photosynthetic machinery and kick carotenoid pigment production into overdrive to give the ripening fruit its characteristic yellow, orange or pink peel.

Orange Sections from Wikipedia

I know you’re not supposed to, but let’s compare apples and oranges. Apples and other stone fruit contain a continuous mass of fleshy fruit surrounding the seeds. Oranges and other citrus fruit have segments, seemingly arranged for convenient consumption. Have you ever wondered where these segments come from? Let’s talk about hesperidium (plant biology word of the day meaning citrus fruit type) development from the outside in. The peel and white pith layers surround a chamber called the locule. This chamber is where the seeds will form and is initially filled with air. As the fruit develops, the hair cells grow from the tissue enclosing the locules toward the center of the fruit. These hair cells swell with water, sugar and other flavor molecules as the fruit matures to become the juice sacs within the segments. Each locule is a separate segment of the hesperidium. Check out this graphic and description from the Mildred E. Mathias Botanical Garden at UCLA.

Satsumas From Wikipedia

One of my favorite citrus fruits is the Satsuma (Citrus unshiu), a seedless variety that is cold hardy enough to be grown in the Baton Rouge area. It’s very similar to mandarin oranges or clementines- small, sweet, seedless and easy to peel***. If you are interested in trying them, but have the misfortune of living in a USDA hardiness zone less than about 8a you can order them online from places like Simon Citrus Farm or LaLagniappe. For those of you in Louisiana that would like to grow your own, I recommend checking out the LSU Agcenter citrus portal for more info.

Now, if you were interested enough to click on the Satsuma-ordering links above, you would have noticed bold disclaimers about quarantines and shipping restrictions. Don’t worry, you don’t have to fear for your safety, but you do if you are a citrus tree. This is because citrus trees have some formidable pathogens that growers and researchers are working hard to combat. Diseases like Sweet Orange Scab and Citrus Canker cause cosmetic damage to the fruit and reduce yields. Sweet Orange Scab is caused by a fungus (Elsinoë australis), and Citrus Canker is a bacterial disease (Xanthomonas citri). Both of these pathogens infect many citrus varieties. Fungicide application protocols can be used to control Sweet Orange Scab, but quarantine and local disposal of infected tissues are also key strategies to prevent their spread.

Citrus greening diseased mandarin oranges Credit: D-USGOV-USDA-ARS. T.R. Gottwald and S.M. Garnsey via Wikipedia

The most devastating pathogen for citrus growers is the bacterium Candidatus Liberibacter spp, which causes Citrus greening disease. It leaves the fruit half green and turns it inedibly sour and bitter. Eventually, the entire tree is killed. The bacterial pathogen is transmitted by an insect vector and growers must spray increasingly more pesticides and destroy acres of infected trees to control the spread of this disease. These factors (reduced supply and increasing costs of maintaining the orchards) are wreaking havoc on the citrus industry, especially in Florida. Growers and scientists are working fervently to come up with some solutions to save the citrus industry. One controversial option is introducing transgenic oranges with resistance to Citrus greening disease. The struggle of associating this wholesome fruit with the GMO debate has been eloquently covered in an article by Amy Harmon in ‘A Race to Save the Orange by Altering Its DNA.’ Genetic engineering may be the only strategy able to combat the disease on a timescale that can save the industry, as evidenced from this quote in the article.

“An emerging scientific consensus held that genetic engineering would be required to defeat citrus greening. “People are either going to drink transgenic orange juice or they’re going to drink apple juice,” one University of Florida scientist told Mr. Kress.”

Let’s hope that growers and scientists can come up with a reasonable solution to this epidemic before the Christmas Orange tradition becomes nothing more than a footnote of Yuletide folklore.

Johnna

*This year’s match-up is Ohio State and Clemson. While I have some University of Michigan connections, I may still have to root against Clemson because I am still bitter about their win over LSU in the 2012 Chick-Fil-A bowl.

** Broccoli and kiwi have nearly twice the Vitamin C content.

***Ease of peeling is a highly desirable trait for the fresh fruit market. Who wants to spend a lot of energy tearing into the fruit, ripping most of it to shreds while getting squirted in the eye with acidic juice in the process? Varieties like Satsumas and Clementines have very thin pith layers that make it easy to pull apart the peel from the segments. For other citrus fruits, the peeling process is not so easy and it frustrates fresh fruit eaters and processors alike. Don’t worry, scientists are on it. Check out this review on orange peeling technologies.

References and Links:

http://www.nass.usda.gov/Publications/Todays_Reports/reports/cfrt0913.pdf

http://www.nass.usda.gov/Statistics_by_State/Florida/Publications/Citrus/cit/2013-14/cit1213.pdf

http://en.wikipedia.org/wiki/Citrus

http://en.wikipedia.org/wiki/Orange_%28fruit%29

http://en.wikipedia.org/wiki/Limonene

http://www.botgard.ucla.edu/html/botanytextbooks/economicbotany/Citrus/

http://aggie-horticulture.tamu.edu/syllabi/422/422lab3.htm

http://en.wikipedia.org/wiki/Satsuma_%28fruit%29

http://www.lsuagcenter.com/en/crops_livestock/crops/citrus/Citrus+and+Freezing+Temperatures.htm

http://www.lsuagcenter.com/NR/rdonlyres/0AD09A71-2C58-40BB-88DB-3D75F2A82C56/74234/pub3169CitrusScabsHIGHRES.pdf

http://www.lsuagcenter.com/NR/rdonlyres/4A42C4A3-BB1B-4DAF-91C3-FB4B675BC393/94853/pub3269citruscankerfactsheet.pdf

http://en.wikipedia.org/wiki/Citrus_greening

http://www.lsuagcenter.com/en/crops_livestock/crops/citrus/How+to+scout+for+the+asian+citrus+psyllid+and+greening+disease.htm

http://www.npr.org/blogs/thesalt/2013/12/27/257632396/time-is-running-out-to-save-floridas-oranges

http://www.nytimes.com/2013/07/28/science/a-race-to-save-the-orange-by-altering-its-dna.html?pagewanted=all&_r=0

The Twelve Days of Christmas Plants: Chestnuts

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

“Chestnuts roasting on an open fire

Jack Frost nipping at your nose

Yuletide carols being sung by a choir

And folks dressed up like Eskimos”

The Christmas Song

American Chestnut Nuts with Burrs and Leaves. Photo by myself: Timothy Van Vliet 2004 from my Orchard in New Jersey (Photo credit: Wikipedia)

The lyrics to The Christmas Song were written during the summer of 1944 and recorded by Nat King Cole in 1946. They were meant to be the acme of the spirit of the winter season. How much do you know about the tree behind the tradition? The American Chestnut’s story of loss and the brink of hope seems almost too fitting for the Christmas season.

By the time those lyrics were written, the American Chestnut (Castanea dentata) was nearing extinction. The forests of the Eastern United States were once filled with this fast-growing species with numerous specimens reaching nearly 100 feet tall and 10 feet in diameter. It provided sustenance for deer, turkeys, bears and passenger pigeons. Its wood was used for a variety of purposes since it was both lightweight and strong. Logging was not the cause of the demise of the American Chestnut.

American Chestnut, Central Maryland. Photograph supplied by the United States Forest Service. (Photo credit: Wikipedia)

English: Range map of American chestnut (Castanea dentata). (Photo credit: Wikipedia)

In 1904, American Chestnuts in the Bronx Zoological Park were reportedly dying, infected with a Chetsnut blight fungus (Cryphonectria parasitica). It was determined that this pathogen had been imported to the United States along with chestnut trees from Asia. Because those varieties had long coexisted with the fungus, they had immunity to the disease, but our American Chestnuts were woefully susceptible. By the 1940s, the fungus had spread throughout the entire range of the American Chestnut. Once infected, the trees died within a decade as the fungus cuts off the lifeline connecting the photosynthetic leaves to the rest of the tree. Because the fungus didn’t completely kill all the roots, the trees vainly sprouted new shoots from the stumps, but eventually these too would fall victim to Chestnut blight. By 1950, nearly 4 billion trees were dead. The loss of the American Chestnut not only changed a Christmas tradition, but also drastically altered the composition of our Eastern forests as slower-growing species like oaks began to fill the empty ecological niche.

Very few specimens of American Chestnuts survive today, and their discovery is always newsworthy. Adult trees have been identified in Ohio, Tennessee, Alabama, Kentucky, Pennsylvania and Georgia. These specimens have escaped infection for a variety of reasons including micro-niche conditions and possibly superior genetics. The largest stand of American Chestnuts can be found in West Salem, Wisconsin. These were planted by an early settler in the area, and because they are outside the natural range of the American Chestnut, they largely escaped the blight. However, in 1987 scientists discovered that even these trees had become infected, and they have been the focus of intense research efforts to save them.

A number of different strategies are being used to ensure that the American Chestnut does not permanently disappear. The American Chestnut Foundation is coordinating restoration efforts. One strategy involves back-crossing American Chestnuts with the blight-resistant Chinese Chestnut. By crossing these two varieties, disease-resistance is conferred. These offspring are then back-crossed to the American Chestnut six more times, selecting for blight-resistance along the way. By 2005 the program had yielded the first blight-resistant chestnuts that were 15/16ths American Chestnut. Because these offspring are 94% American Chestnut, they retain many of the properties of this species. These are being re-introduced in test plots by the U.S. Forest Service. As of this year, nearly 80% of the back-crossed saplings are surviving. Other breeding studies are being conducted with the remaining wild specimens of American Chestnut trees.

More modern technologies are even being applied for the salvation of the American Chestnut. In an NSF-funded project, the genomes of various tree species including the American and Chinese Chestnuts have been sequenced in order to identify the specific genes involved in blight-resistance. This knowledge will provide better genetic markers for screening in traditional breeding programs as well as target genes for engineering. To facilitate these efforts, researchers have developed new techniques for propagating and transforming American Chestnut plant material. As scientists learn more about plant disease resistance in other plant species (like crop plants), those genes also become candidates for engineering into the American Chestnut. For example, transgenic American Chestnuts containing a gene from wheat that helps confer resistance have been planted for field tests. Hopefully the genome of the Chinese Chestnut will reveal additional resistance genes that can be introduced transgenically.

Scientists are also using other methods to tame the Chestnut blight fungus. One way to combat the microbe that felled the giant trees is by using another microbe- a naturally-occurring virus that attacks the Chestnut blight fungus. This is a method that may save mature trees already infected with the fungus like those in West Salem, Wisconsin. It works to heal infected trees in a way similar to modern human vaccinations. Scientists isolate the virus from other infected American Chestnuts and inoculate blight-infected trees. The virus weakens the fungus enough so that the trees can recover. The initial results have proven promising, but this is not the magic bullet solution that they were hoping for.

With all of these efforts, roasting chestnuts over an open fire may once again be a common American Christmas tradition, but science still has a long way to go to bring this species back from functional extinction. Even then, it remains to be seen whether crossbred or transgenic (aka GMO) American Chestnuts will be accepted by the general public. However, there does seem to be some poetic justice in a restoration solution that involves a small piece of foreign DNA to protect these giant trees from a foreign deadly microbe.

Johnna

References and Links:

http://dendro.cnre.vt.edu/forsite/paul/paul1.htm

http://en.wikipedia.org/wiki/American_chestnut

http://www.esf.edu/chestnut/background.htm

http://www.fs.fed.us/r8/chestnut/qa.php

http://dnr.wi.gov/wnrmag/html/stories/2002/aug02/chest.htm

http://aobblog.com/2013/10/american-chestnut-returns/

http://www.acf.org/pdfs/education/TheLegendoftheAmericanChestnutTree.pdf

http://www.acf.org/pdfs/about/restoration.pdf

http://www.acf.org/pdfs/news_room/Blight%20Resistance.pdf

http://blogs.usda.gov/2013/12/06/restoration-efforts-may-mean-more-chestnuts-roasting/