July 23, 2016 | David F. Coppedge

For the Love of Trees

You don’t have to be a proverbial tree-hugger to love trees and wonder at all the things they can do, and do for us.

India just broke a world record by planting 50 million trees in one day, National Geographic reported. Wow! Other countries are on the tree-planting binge, too. Why would people do such a thing? “Trees sequester carbon dioxide from the air, thereby reducing the amount of greenhouse gases in the atmosphere,” but they provide many other benefits, too. Besides, they are wonders of engineering in their own right, and often beautiful.

Google Tree: You may have marveled at how trees find ways to grow out of the poorest of soils—even out of bare rock, it appears sometimes. That’s because trees have a search strategy: actually, several strategies. If there’s a nutrient hotspot around, PhysOrg says, they will find it. How can they do this without eyes and ears and noses? Well, they have help. Fungi are their partners. But fungi don’t have those things, either. A new paper in PNAS shows how “Root morphology and mycorrhizal symbioses together shape nutrient foraging strategies of temperate trees.” For the curious,

Here, we show that in 13 sympatric temperate tree species, when nutrient availability is patchy, thinner root species alter their foraging to exploit patches, whereas thicker root species do not. Moreover, there appear to be two distinct pathways by which thinner root tree species enhance foraging in nutrient-rich patches: AM trees produce more roots, whereas EM trees produce more mycorrhizal fungal hyphae. Our results indicate that strategies of nutrient foraging are complementary among tree species with contrasting mycorrhiza types and root morphologies, and that predictable relationships between below-ground traits and nutrient acquisition emerge only when both roots and mycorrhizal fungi are considered together.

River tree: What transports 8 to 10% of the Yukon River’s annual discharge? It’s the trees in boreal forests, Science Daily reports. A team from the University of Alaska made measurements and found that trees, by soaking up snowmelt and transpiring it into the atmosphere, play a larger-than-expected role in the boreal water cycle, especially between late winter and spring. Even deciduous trees before they leaf out in the spring do a lot of water transport work, releasing 21-25% of the available snowmelt water.

Coconut homes: The fruits of coconut trees, as we all know, have hairy, waterproof husks that allow the seeds to float across oceans. Science Daily says that the “specialised structure of coconut walls could help to design buildings that can withstand earthquakes and other natural disasters.” Those coconut palms are quite the structural engineers:

Their investigations found that within the endocarp layer — which consists mainly of highly lignified stone cells– the vessels that make up the vascular system have a distinct, ladder-like design, which is thought to help withstand bending forces. Each cell is surrounded by several lignified rings, joined together by parallel bridges. “The endocarp seems to dissipate energy via crack deflection” says Stefanie. “This means that any newly developed cracks created by the impact don’t run directly through the hard shell.” It is thought that the angle of the vascular bundles helps to “divert” the trajectory of the cracks. The longer a crack has to travel within the endocarp, the more likely it is that it will stop before it reaches the other side.

Other Plants

The wonders of plant biology extend down to smaller species, too. Here are some more plant wonders:

Plants as chemistry labs: Most people probably are unaware of the thousands of the complex organic chemicals manufactured by plants. The refreshing pine-scented air we enjoy when walking in the woods doesn’t just happen. Volatile compounds, particularly terpenes, are made by plants for themselves and for the whole forest community. PNAS gives us a glimpse into the remarkable complexity of processes that go on daily in the laboratories inside plant cells:

The triterpenes are a large and highly diverse group of plant natural products. They are synthesized by cyclization of the linear isoprenoid 2,3-oxidosqualene into different triterpene scaffolds by enzymes known as triterpene synthases. This cyclization process is one of the most complex enzymatic reactions known and is only poorly understood. Here, we identify a conserved amino acid residue that is critical for both product and substrate specificity in triterpene synthases from diverse plant species. Our results shed new light on mechanisms of triterpene cyclization in plants and open up the possibility of manipulating both the nature of the precursor and product specificity, findings that can be exploited for the production of diverse and novel triterpenes.

The plant that solves Rubik’s cube: Science Daily tells about an enzyme in plants that solves puzzles. “Scientists at the John Innes Centre have discovered a key ‘twist’ in a Rubik’s cube-like plant puzzle, which could pave the way to new, or more effective pharmaceuticals,” the article begins. To make one of the many complex chemicals plants are famous for, called heteroyohimbine, the plant has to twist and turn the molecule. “The puzzle is not a simple jigsaw in which the picture becomes clearer with each new piece discovered; it’s more like a Rubik’s cube.”

Sunbathing plants: Why don’t plants get sunburn? They stand out there making shade for others, but are exposed to the hot sun all day. Nigel Paul explores this question on The Conversation and reports that plants make their own sunscreen. Clever! They are, after all, good organic chemists as stated above. The dangerous ultraviolet-B rays (UVB) act as a signal to a protein named UVR8 to turn on their sunscreen production. How many plants had to burn up before that system evolved?

Drought-resistant corn: Californians know about this one, looking at their brown lawns after years of drought. Grass isn’t entirely helpless under the onslaught of dry conditions. A paper in PNAS says that grasses like maize are able to suppress shoot-borne roots during drought to conserve water. To do this, the roots and the top of the plant have to talk to each other—and they do, with chemical messages traveling through the pipelines.

Nitrogen fixing skill: Many plants (especially legumes, like beans and peas) help the whole planet by “fixing” nitrogen—that is, making the molecular nitrogen gas in the atmosphere available in the form of ammonia and other compounds. N2 in the atmosphere, being triple-bonded, is a tough nut to crack. Current Biology reveals a few more details about the process in soybeans. It “requires complex adjustments of nodule nitrogen metabolism and partitioning processes,” the paper says. If and when scientists can ever replicate what plants do every day, it could revolutionize agriculture.

The force: When plant cells divide, they have a problem. Stiff cell walls don’t make way for new cells easily. What to do? Chilean scientists took a look at the forces involved in cell division in plants. Writing in PNAS, they report on recent work that helps resolve a long-standing debate between two hypotheses. It appears now that “the cell will align its division plane with the direction of greatest tension as a whole.” Even so, the scientists are still not sure the process is understood. Maybe both hypotheses are partly right.

Light food: The greatest benefit to man and to all animals is plants’ ability to make food from sunlight. Scientists still struggle to understand photosynthesis in detail. Science Daily reported new clues that could help scientists harness the potential of this amazing ability. The clue involves enzymes and signals and wavelengths of light beyond the scope of a quick summary. Too bad they didn’t thank the Creator.

BM-lightclick“Photosynthesis usually ranks about third after the origin of life and the invention of DNA in lists of the greatest inventions of evolution,” said Bryant. “Photosynthesis was such a powerful invention that it changed Earth’s atmosphere by producing oxygen, allowing diverse and complex life forms — algae, plants, and animals — to evolve.

Incredible egg: Speaking of “plant evolution,” detail freaks may be curious how Current Biology answers the question, “What does it take to be an egg?” In his latest book Evolution: Still a Theory in Crisis, Michael Denton pointed to plant reproduction as a prime example of “baroque” architecture too elaborate to submit to a Darwinian mutation-selection explanation (Discovery Institute’s short video “Biology of the Baroque” explains what that means). The authors of the new paper point to a conserved transcription factor in liverworts that appears to be implicated in cell fate during egg cell production, but they admit, “The genetic regulation of cell patterning within plant gametophytes remains poorly understood.”

Anyone see Darwin contributing anything worthwhile to the findings of science listed above? Anyone?

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