On August 21st, 2017 we learned about

Thin, smooth bark makes Madrone tree trunks seem cool to the touch

I may need to start petting trees more often. I’ve long known of trees that had particular colors and smells in their leaves and trunks, but I only learned in the last week that some trees hold surprises for your finger tips to discover. The tree in question was a Pacific Madrone (Arbutus menziesii), and was actually hard to miss thanks to its striking red bark peeling off the trunk. The surprise was that the tree was cool to the touch, which is why it’s sometimes called the “refrigerator tree.”

For something cool to the touch, Madrone trees need lots of sunshine to thrive. If conditions are right, they can grow to be nearly 100 feet tall, but at smaller sizes Madrone trees can be mistaken for some of their red-barked relatives, like the Manzanita (Arctostaphylos). Both plants’ eye catching bark grows thin and smooth, but this trait is especially striking in mid-summer when Madrone tree bark starts to peel off the trunk. At that point, a quick touch makes it hard to ignore how much cooler these trees are than the surrounding environment.

Cold or just conductive?

Except that they’re not really cooler. The trees’ temperature is likely the same as any of the other similarly-sized plants that grow near them, just like a paper book is the same temperature as a metal keys sitting in the same room. With sufficient time, the temperatures equalize, but when we touch the metal, or the Madrone trunk, it feels colder. This is because heat is more easily transferred to certain materials than others, and when heat from our hand is conducted away we perceive it as colder. Now, a Madrone tree obviously isn’t metal, but that thin, smooth bark isn’t as good an insulator as the rough, corky bark that you find on most trees. Your hand is able to come into more contact with the smooth surface, and the sap and fluids flowing inside the trunk can then wick your body heat away.

Even if refrigerator trees aren’t actually colder, their unusual bark obviously still stands out from that of their neighbors in the forest. The thin, peeling bark that exposes the trunk may have originally evolved as a form of defense. By shedding the outer layer of bark, the tree can dump any fungi, mosses, lichens or other parasites that tried taking up residence on the red wood. The red itself is likely another form of defense, as the tannins that make up that coloration would be bitter and possibly toxic to animals that might want to munch on the tree, not unlike the colorful bark found on rainbow eucalyptus. It’s good that the peeling is helpful to these plants, because now that they know about these chilled trees, it’s going to be hard to keep my kids’ hands off them.

Source: The Refrigerator Tree by Steve, Nature Outside

On August 20th, 2017 we learned about

Digital farming tools simulate a full season’s growth in a single day

Humans have been manipulating the evolution of plants for ages, but usually at a pace slow enough we barely notice. By planting seeds from specific plants that had attributes we liked more than others, say a more pleasing color, or larger amount of tasty flesh, we’ve transformed many plants into the produce we know today. However, this is a slow process, and farmers are looking for ways to speed things up while reducing the costs associated with experimenting with a whole season’s crops. The solution may be to first grow crops on a in silico, or “in silicon chips,” before ever putting a seed in the ground.

The simulations that are being developed allow for some very specific details to be tested. For instance, will you get a bigger crop yield if you plant your sugarcane in staggered rows, or all lined up? Should they be angled north-south, or east-west? A farmer could plant four different fields of sugarcane to see which did best, although in doing so they might introduce new variables to the mix. It would also be a slow process, possibly risking income for 12 months of work.

The in silico version took all the available data and came up with a prediction in 24 hours. It considered minutiae down to the amount of light that might be blocked by a neighboring plant’s leaves at different times of the day, then produced a 3D visualization to show the expected outcome of each field arrangement.  In this case, staggered plants planted on a north-south axis was predicted to increase yields by ten percent, making that a much safer test to run in the real world for confirmation.

Farming experiments made even faster

As these tools are developed, researchers hope that the speed and depth of the simulations can be improved. Not everyone can tie up a supercomputer for 24 hours to test out a new technique, and the goal is to eventually simulate a whole season’s growth in a minute, making it easier to try out different variables. The number of variables should also be increased to incorporate more data that different labs have been creating over the past decades, but that requires some serious coordination efforts. Not every research team uses the same tools or data structure to archive their experimental findings, which makes integrating existing information about crops difficult.

Still, the developers are confident that all these challenges can be met, partially because they have to. Concerns over population, soil quality and fresh-water availability suggest that farms will need to be more efficient than ever in the coming years. A tool that lets you configure and simulate new ideas in a single afternoon could save everyone a lot of time and resources.

Source: Growing Virtual Plants Could Help Farmers Boost Their Crops by Leslie Nemo, Scientific American

On August 8th, 2017 we learned about

Cocoa plants get protection from their healthy neighbors’ leftover leaves

The next time you’re about to enjoy a bite of chocolate, take a moment to thank the fungi and other microbiota that made it possible. Like the microbes humans start picking up at birth, organisms like Colletotrichum tropicale come to live on cocoa plants, helping them be more resilient to pathogens that would otherwise destroy the plant. Fortunately for farmers, and chocolate lovers, experiments suggest that this kind of fungal protection isn’t hard to spread between cocoa plants— sharing a bit of leaf litter from healthy neighbors should do the trick.

One of the biggest concerns for a cocoa, papaya and other tropical plants is Phytopthora palmivora, the “plant destroyer.” Once infected, a plant will start rotting at a variety of locations, from the roots to the fruit, and thus is a huge problem for farmers. The pathogen can be found in soil and water throughout tropical ecosystems, but fortunately protective fungi like C. tropicale aren’t too hard to come by either. Just as microbes can be shared between people when they touch, contact with leaf litter from healthy plants seems to be a good way to spread preferred microbes.

Testing leaf-based transmission

Researchers tested the effectiveness of leaf litter with cocoa plants initially grown from sterile seeds in sterilized chambers. Their leaves were verified as being fungus free before one-third of the plants had dead leaves from healthy cocoa plants placed in their pots. Other plants got mixed leaves from the forest, and some had none at all. They were all given a little time to grow outdoors in more “natural” conditions before purposely being exposed to P. palmivora. After three weeks, the plants with healthy cocoa leaves on their soil fared the best. DNA sequencing also confirmed that these plants leaves had a considerable population of the helpful fungus, C. tropicale.

While growing up in the leave litter of a healthy plant seems beneficial, there are limits to proximity. If a parent plant is infected, it can just as easily spread pathogens to its offspring. So cocoa farmers need to keep an eye on their plants to make sure the healthier plants are the ones dumping their leaves their neighbors.

Source: Litter Bugs May Protect Chocolate Supply, Scienmag

On August 7th, 2017 we learned about

Light pollution is driving nocturnal pollinators away from their favorite plants

Plants need light to grow, but many need a good dose of darkness as well. This is because some very effective pollinators wait until dark to visit plants’ flowers, meaning that a plant can work on reproduction night and day, growing more seeds for new plants. This has served plants well for millions of years, and a variety of very effective pollinators only come out at night, from moths to beetles to bats. Unfortunately, recent experiments in Switzerland indicate that humanity’s love of lighting may be casting a shadow over this otherwise efficient system.

The basic model to be tested was that artificial lighting is scaring nocturnal pollinators away from their favorite flowers. Setting up this experiment was tricky though, as artificial lighting in developed areas has left very few places in total darkness at night. This forced researchers from the University of Bern to head for the foot of the Alps to find some cabbage thistles (Cirsium oleraceum) that still enjoyed a decent amount of darkness each night, at which point they started shining lights on them. Half the thistle plants were left in natural conditions and monitored with night-vision goggles, while the others were illuminated by semi-portable LED lamps meant to imitate a streetlight, albeit one with a very long extension cord.

Staying out of the spotlight

Pollinators were counted and collected each night, and the various nocturnal critters clearly showed a preference for the dark. There were 62 percent fewer visits by pollinators, and 29 percent less variety among the pollinators that did risk exposure in the lights. Even though daytime pollinators visited both sets of thistles equally, the plants that missed their nighttime visitors showed a significant decrease in the number of seeds they produced. The decrease in seeds actually outweighed the decline in pollinator visits, suggesting that nighttime pollinators may do a better job of moving pollen on a per-visit basis. In other words, adding more bees and butterflies during the day wouldn’t easily replace the lack of moths and beetles at night.

One hope is that the plants still left in darkness are getting extra pollinator traffic from all the visitors that are scared off by human-made lighting. However, the pockets of darkness left in some areas are so isolated in many places that these more successful plants probably won’t make up for the losses experienced by their well-lit counterparts. This isn’t the only concern that’s been raised about artificial lighting, indicating that we may have to reconsider how badly we really need all our outdoor night-lights.

Source: Artificial Light Deters Nocturnal Pollinators, Study Suggests by Scott Neuman, The Two-Way

On July 12th, 2017 we learned about

Tomatoes infuse their leaves with toxins to turn insects against each other

Tomato plants do not want to be eaten. The 31 pounds of tomatoes each American gobbles per year is fine, because that helps with seed dispersal and gives us a reason to plant more tomatoes. The problem for the plants is that too many bugs bypass the red fruit and eat the leaves of the plant, leaving it with no way to produce its own food through photosynthesis. To defend themselves, the plants have found a way to control the bugs’ appetites and populations— they get the bugs to eat each other.

This pest-control concept is actually based on normal behavior in various pest herbivorous insects, like mottled willow moth caterpillars (Spodoptera exigua). When these bugs can’t get enough nutritious food, they don’t really have the means to travel to find something better, as they’re trying their best to hoard calories in preparation for metamorphosis. So when the leaves are scarce, or just low enough quality, the insects will start eating each other instead as the last local source of nutrients and calories.

Turning up the toxins

Tomato plants (Solanum lycopersicum) have evolved to exploit this quirk of pest ecology. Tomatoes in danger can start producing extra toxins in their leaves that make them less nutritious to eat. Manipulating leaf-quality like this then convinces caterpillars it’s time to switch to cannibalism. In experiments, caterpillars offered more toxic leaves started munching caterpillar corpses much sooner than their peers. From the tomato plant’s perspective, adjusting the chemistry of leaves may be energetically costly, so they don’t make their leaves less attractive all the time. When circumstances demand it, this strategy does work well enough to make a measurable difference in just how much each plant gets eaten.

The last layer of this defensive strategy is that a tomato plant doesn’t need to get bitten to start raise its defenses. Like a variety of other plants, tomato plants can warn each other about the arrival of herbivores. They emit a compound called methyl jasmonate (MeJA) that can be detected by nearby plants, giving them a chance to start toxifying their leaves before the insects begin their buffet. There is some interest in manipulating this warning system, since presumably farmers could release MeJA to warn crops whenever they wanted. However, it might be best to follow the tomato plants’ lead on this, since constant warnings and toxic leaves could stress the plants while selecting for only the hardiest, toughest insects around.

Source: Plants turn caterpillars into cannibals by Laura Castells, Nature

On July 10th, 2017 we learned about

Plants and fungi that spray, splatter and sling their seeds and spores

If the apple doesn’t fall too far from the tree, they both have a problem. The seeds in the apple may take root next to its parent where it will be forced to compete for nutrients and sunlight, possibly stunting its growth and wasting the investment the parent plant made in the seeds. Fortunately for apples, the seeds are packaged in yummy, sugar-filled fruit that animals eat, taking the seeds for a ride along the way. As those seeds are pooped or discarded elsewhere, the seeds have a chance to grow in new territory away from their parents. Not all plants make such attractive fruit though, and so many have had to find other ways to give their offspring a push to newer pastures. In some cases, that even means evolving mechanisms to squirt, eject or catapult seeds and spores to ensure a bit of distance between each generation.

Shooting spores

Starting small, many fungi have ways to launch their spores into the air when it’s time to reproduce. The Pilobolus mold, for instance, uses sap to build up pressure in a stalk called the sporangiophore. Once the pressure is too great to contain, the end of the sporangiophore bursts open, launching a payload of pinhead-sized spore capsules. Those tiny capsules are ejected at up to 55 miles per hour, sometimes traveling as far as six feet. For molds that grow less than half an inch high, that’s plenty of distance to ensure the spores end up on the grass they need to continue their life-cycle.

Slinging sori

On a larger scale, some plants throw their spores rather than fire them out of a fluid-powered cannon. The delicate ferns you find in shady forests have a two-stage life-cycle, and to get spores in a safe location to grow into gametophytes, the spores need to move away from the parent plant. To do this, clumps of spore pellets, called sori, grow on the underside of the fern’s leaves. Once the sori dry out, the a catapult mechanism flings them into the air where they can be carried on the wind, animal fur, or in local waterways.

Ferns don’t exactly look like catapults, but they can launch their spore in a process that takes less than a half-second to complete. A coiled group of cells called an annulus grows around spore capsules, bent in an arch to build a bit of mechanical tension. Once dried sufficiently, the annulus snaps forward to lob the spore capsule. To keep it from bending too far and flinging the spore back at the leaf, a tiny amount of water squeezes through pores in the annulus, blocking that forward movement and releasing the spore at an optimal trajectory. This tiny delivery structure can send spores flying at around 22 miles per hour once released.

Popping pods

Launching spores are one thing, but firing full-sized seeds into the air requires some heavier artillery. Various plants grow seed containers that dry out unevenly, squeezing the seeds from one side. For example, when gorse seed pods are sufficiently dried out, they fire seeds out at around 18 miles per hour. Gorse seeds usually only travel a few feet, but pinching seeds for propulsion is used by the Bauhinia tree to send seeds as far as 49 feet.

Self-firing fruit

The biggest payload to be propelled off a plant may be Ecballium elaterium, better known as the Squirting cucumber. Like the cucumber you put on your salad, this plant’s seeds grow in a protective, oblong fruit, although there’s a lot less flesh to actually eat. Instead the two-inch fruit fills mostly with fluid, with enough room for a 20 or so seeds to go flying away from the parent plant.

When filled with fluid, there’s enough pressure in a single cucumber to give it a bit of a hair trigger, ready for wind or a passing animal to kick things off. When “activated,” the cucumber will detach from the stalk it grows on, ejecting water and seeds into the air out of newly formed opening where the stem attached. Like a rocket booster, the cucumber shell will be pushed towards the ground while the seeds will fly as far as 20 feet away. It seems like this should make for the most exciting, kid-pleasing vegetable ever, but aside from being mostly water, Squirting cucumbers contain a lot of cucurbitacins, pest-deterring chemicals which are toxic if ingested. It seems that Squirting cucumbers are better to watch than to eat.

Source: An explosive start for plants: Plants get up to some ingenious tricks and aerial acrobatics to ensure their survival by Paul Simons, New Scientist

On May 29th, 2017 we learned about

Tree-climbing goats spit out the argan seeds humans want to harvest

Argan oil may soon loose some of its allure, because it turns out it’s not tied to goat poop as much people thought. Unlike kopi luwak coffee that put civet-processed beans in high demand, the goats that pluck fruit from the argan trees of Morocco have been proven to be spitting out the oil-rich nuts, instead sending them all the way through their digestive tracts. This isn’t to say that the goats are doing some very specialized nut-collection, but experimental evidence has taken poop out of the equation.

The nut-gathering goats may look perfectly ordinary at first glance, but their efforts to harvest the fruit and leaves of an argan tree (Argania spinosa) are fairly amazing. With dexterity worthy of (unrelated) cliff-dwelling mountain goats, these domestic goats will climb trees as high as 30 feet high, staying in the upper branches until a tree has been nearly stripped bare. The goats seem to like the green, fleshy fruit that resembles a large olive, even though it contains a large nut inside. It may take a bit of digestion, but rather than allow the nuts to be passed all the way through the digestive tract, the goats elect to regurgitate the seeds, spitting them out where humans can scoop them up to make oil, dips and of course, upscale beauty products.

Examining goat excrement

To determine exactly how digested the argan nuts were, researchers fed domesticated goats a variety of fruit, monitoring exactly which seeds came out which end of the animal. As ruminants like cows and sheep, goats digest their food throughout four stomachs, regurgitating and re-chewing cud between each phase of digestion. This means that even if the argan fruit was swallowed in the trees, the now-bare nuts weren’t guaranteed a trip through the goats’ entire digestive tract. In testing the goats’ preferences, researchers found that smaller seeds didn’t seem to be noticed, eventually turning up in the goats’ feces. Larger seeds, like those of the argan tree, were rejected and spat out, rather than being reswallowed. So it seems that despite popular lore about the post-poop qualities of Aargan oil, these nuts had only been partially fermented by the goats.

This is mixed news for all the parties involved. The argan trees benefit from this form of seed dispersal, which is common enough in other ecosystems to earn the name endozoochory. If this makes the resulting products seem less special, it may actually be good news for the goats, as the aforementioned coffee made from civet poop was in enough demand to land many wild civets in cramped, inhumane cages for easier harvests. For the herdsmen who gather the goat-gobbled argan nuts, it’s probably a tad more pleasant to pick up spat seeds, although they’ve likely known this all along. If anything, the goats make harvesting these valuable seeds so easy, there are actually concerns about the over-saturation of goat herds among argan trees. Now that the news is out, we’ll see if demand for argan oil declines, which may help over-harvested trees while also revealing some very weird standards for what people want to wipe on their faces.

Source: Tree-climbing goats spit out and disperse valuable argan seeds by Elizabeth Preston, New Scientist

On April 17th, 2017 we learned about

The potentially perilous seed pods of a Sweet Gum tree

It may sound ridiculous at first, but my four-year-old had to go to urgent care last week because of something called a Sweet Gum ball. The name may suggest this emergency was oriented around candy, but Sweet Gum balls, also known as “space bugs,” “monkey balls” or “goblin bombs,” aren’t something you’d want in your mouth. They’re one-and-a-half-inch seed pods from a Sweet Gum tree, covered in woody spikes and famous for littering yards all over suburban America. In this case, a good fall managed to break open my kids’ forehead enough to require surgical glue, so it seemed like a good reason to learn more about what’s growing in the yard.

While the seed pods may decidedly unpleasant to have against your skin, the Sweet Gum trees (Liquidambar styraciflua) they come from are actually quite nice. Characterized by deep-grooved, “alligator skin” bark, five- to seven-pointed leaves and a pleasing overall shape, these trees have been planted in many neighborhoods as ornamental landscape pieces. The trees are especially picturesque in the late fall, when their leaves turn gold, purple and red, and are relatively pleasant to see all over the ground afterwards.

Uses beyond appearances

None of this is especially sweet or gummy of course, but the name is actually based on what’s inside the tree, not outside. The resin in the Sweet Gum tree has been linked to a huge variety of medicinal treatments. Explorer Francisco Hernandez claimed it could treat gonorrhea, diphtheria, and indigestion. Other applications focused around skin conditions or dysentery. The Cherokee even used the sap to help treat wounds, probably including those inflicted by the tree’s seedpods.

Not many people are relying on the tree’s sap for curatives these days, but many are dealing with the seed pods. In the spring and summer, a tree is likely to grow and drop what feels like an overwhelming supply of the tough, spiked balls. The large spikes, which may have once helped latch the balls onto some long-lost megafuana’s fur now only serve to keep larger animals from easily accessing the sides inside the pod. Smaller birds and squirrels have found ways to access the seeds, but that ecological utility isn’t quite enough for some people. To cut down on the risk of puncture wounds, some people are injecting their Sweet Gum trees with what is effectively birth control, stopping them from producing the seed pods in the first place.

My second-grader said: I use them as pencil-sharpeners by twisting a pencil into the empty seed holes.

That may be one of the less common uses of a Sweet Gum ball, but people are definitely interested in putting them to work. They can be used in gardening to defend plants, help drain soil, or add to compost. They’re also used in a lot of craft projects, often focused around wreaths or ornaments. If you have an idea, or a need for a very uncomfortable pencil-sharpener, you can always order a bag of balls without investing in an entire tree.

Source: The Most Dangerous Tree in the Suburbs by W. Kerrigan, American Orchard

On April 5th, 2017 we learned about

Sourcing the chemical components of trees in California

A redwood tree usually weighs around 50,000 pounds, which can yield as much of 250 cubic feet of usable lumber. That’s a lot of mass, and if you were considering a 50,000 pound animal, it would be hard to not take an interest in that creature’s dietary needs (if only to make sure you weren’t one of them.) We know what trees take in, but in some cases it’s not clear how trees might be satisfying their nutritional needs. Analysis from the Sierra Nevada mountains found that the giant sequoias living there aren’t always shopping local, taking in nutrients from as far away as the Gobi Desert in China.

Long-distance dirt

The major question for giant trees like sequoias or redwoods is phosphorus. These giant trees grow mostly on soil made from granite bedrock, which shouldn’t have enough crucial nutrients like phosphorus to sustain such large plants. Rather than carve into living trees, researchers figured they could collect a sample of what soil was circulating in the mountains with pans designed to collect dust. The dust might not represent deeper layers of soil exactly, but it would give a fair representation of what elements were available to the trees living there.

The dust collected was then analysed, using the isotopes of each component to figure out its point of origin. At higher elevations, 45 percent of the dust originated in Asia, having been blown high into the atmosphere to cross the Pacific Ocean. At lower altitudes, Asian dust was less concentrated, and more dust was seen from California’s own Central Valley. While the Asian dust made the bigger journey, the Californian dust was actually more surprising. As the study progressed, more Central Valley dust was found at higher altitudes, which researchers suspect was due to drought conditions drying and distributing topsoil more than usual.

Captured carbon

Of course, a sequoia or redwood tree isn’t 25 tons of phosphorus— most of that bulk is carbon, grabbed out of the air’s ample supplies of carbon dioxide. During photosynthesis, trees and other plants break down carbon dioxide, releasing oxygen and building glucose, starch and cellulose. That cellulose (C6H12O6) then locks up a lot of carbon in leaves and well, wood, which is very helpful in a world with an ever-growing surplus of carbon dioxide. On a macro-scale, forests in the United States alone are estimated to absorb around 827 million tons of carbon dioxide each year thanks to their normal growth processes. Since the CO2 is airborne, some of it might also be coming from Asia, but its abundant availability means that it isn’t the ingredient researchers are trying to track down.

Source: Gobi Desert Dust Helps Sustain California's Sierra Nevada by Robert S. Eshelman, Live Science

On March 26th, 2017 we learned about

Purging plant cells turns spinach into scaffolding for heart tissue

Dark, leafy vegetables are great for your health, even if don’t eat them. Researchers at the Worcester Polytechnic Institute are looking to use spinach leaves as a way to help heal damaged heart tissue, although not thanks to any of their vitamin A or iron. Instead, the structure of the leaves themselves may be used as a scaffolding for growing new tissue that can later be grafted to damaged hearts, arteries or bones.

Plants and animal cells have some similarities, but overall operate very differently. Even the basics of metabolism, such how carbon dioxide and oxygen are used, illustrate that you can’t add plant cells to an animal organ and expect them to function, much less avoid rejection and destruction by the body’s immune system. So before any piece of spinach can be put near a heart, all the plant cells must be removed in a process called decellularization. Over the course of a week, a specialized detergent can essentially drain a leaf of the plant cells, leaving a translucent, leave-shaped shell made of cellulose. That cellulose is inert enough that it won’t be rejected by animal cells, and can therefore be repurposed as a starting point for building new animal tissue.

Upside of leafy lattices

The primary benefit of using a spinach leaf in this way is the exact shape of the decellularized structure. The fine veins and capillaries you see in a leaf are an excellent proxy for the vascular system found in animal tissue. Once the cellulose is isolated, it can be refilled with the cells that line blood vessels and will pass fluids to the surrounding cells in a way that can’t otherwise be synthesized. For example, while 3D printing is pushing the boundaries of tissue generation, it can’t yet match the delicate, branching network of capillaries that spinach has already mastered.

Once a single leaf is mastered, larger structures like heart muscles would be made of many layers of “leaves” stacked together. Beyond spinach, researchers are looking to other veggies as scaffolding for other types of tissue. Parsley, sweet wormwood and jewelweed are all contenders for future bioengineering projects. Aside from the immediate practicalities mentioned above, plant-based tissue development may also offer economic and environmental benefits thanks to the relatively easy production of these key ingredients.

Source: Heart tissue grown on spinach leaves, Science Daily