Category: Genetics, Breeding, Growth

Hydro Power Plants

From the soil to the sky: Researchers quantify the amount of energy that plants use to lift water on a global scale: Every day, about one quadrillion gallons of water are silently pumped from the ground to the treetops. Earth’s plant life accomplishes this staggering feat using only sunlight. It takes energy to lift all this liquid, but just how much was an open question until this year.

Researchers at UC Santa Barbara have now calculated the tremendous amount of power used by plants to move water through their xylem from the soil to their leaves. They found that on average, it was an additional 14% of the energy the plants harvested through photosynthesis. On a global scale, this is comparable to the production of all of humanity’s hydropower. Their study, published in the Journal of Geophysical Research: Biogeosciences, is the first to estimate how much energy goes into lifting water up to plant canopies, both for individual plants and worldwide. “It takes power to move water up through the xylem of the tree. It takes energy. We’re quantifying how much energy that is,” said first author Gregory Quetin, a postdoctoral researcher in the Department of Geography.

This energy is in addition to what a plant produces via photosynthesis. “It’s energy that’s being harvested passively from the environment, just through the tree’s structure.” The team combined a global database of plant conductance with mathematical models of sap ascent to estimate how much power the world’s plant life devotes to pumping water. They found that the Earth’s forests consume around 9.4 petawatt-hours per year. That’s on par with global hydropower production, they quickly point out.

Reaching for the Sun

How light and temperature work together to affect plant growth: Plants lengthen and bend to secure access to sunlight. Despite observing this phenomenon for centuries, scientists do not fully understand it.

Now, Salk scientists have discovered that two plant factors—the protein PIF7 and the growth hormone auxin—are the triggers that accelerate growth when plants are shaded by canopy and exposed to warm temperatures at the same time. The findings, published in Nature Communications will help scientists predict how plants will respond to climate change—and increase crop productivity despite the yield-harming global temperature rise.

“Right now, we grow crops in certain densities, but our findings indicate that we will need to lower these densities to optimize growth as our climate changes,” says senior author Professor Joanne Chory, director of Salk’s Plant Molecular and Cellular Biology Laboratory and Howard Hughes Medical Institute investigator. “Understanding the molecular basis of how plants respond to light and temperature will allow us to fine-tune crop density in a specific way that leads to the best yields.”

Genetics, Breeding, Growth

Ferns Get a Genome

Ferns finally get a genome, revealing a history of DNA hoarding and kleptomania: Ferns are notorious for containing massive amounts of DNA and an excessively large number of chromosomes. Defying all expectations, a fern no larger than a dinner plate currently holds the title for highest chromosome count, with a whopping 720 pairs crammed into each of its nuclei. This penchant of ferns for hoarding DNA has stumped scientists, and the intractable size of their genomes has made it difficult to sequence, assemble and interpret them.

Now, two papers published in the journal Nature Plants are rewriting history with the first full-length genomes for homosporous ferns, a large group that contains 99% of all modern fern diversity. “Every genome tells a different story,” said co-author Doug Soltis, a distinguished professor with the Florida Museum of Natural History. “Ferns are the closest living relatives of all seed plants, and they produce chemical deterrents to herbivores that may be useful for agricultural research. Yet until now, they’ve remained the last major lineage of green life without a genome sequence.”

Two teams of researchers separately unveiled the genome of Ceratopteris (Ceratopteris richardii) this Thursday and that of the flying spider monkey tree fern (Alsophila spinulosa) last month.

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Genetics, Breeding, Growth

Heterophylly

Researchers identify gene that participates in leaf response to environmental conditions: Heterophylly, the plasticity of leaf form in response to environmental conditions, occurs in aquatic and amphibious plants where it modulates leaf form, gas exchange and photosynthesis, providing a good model for plant acclimation to environment.

Although heterophylly was widely seen in nature, no transgenic studies have been performed yet and its molecular mechanism is largely unknown. Hygrophila difformis (Acanthaceae) has recently merged as a plant model for the study of heterophylly due to its typical phenotypic plasticity to various ecological factors, but the mechanisms had not been identified.

In a study published in Plant Physiology, a research team led by Prof. Hou Hongwei from the Institute of Hydrobiology (IHB) of the Chinese Academy of Sciences provided genetic evidence on the molecular mechanism of heterophylly in Hygrophila difformis.

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Climate Change Genetics, Breeding, Growth

Epigenetic Reprogramming

Plant molecular geneticists discover, and begin to crack, the epigenetic code: When plants sense environmental challenges such as drought or extended periods of extreme temperatures, they instinctively reprogram their genetic material to survive and even thrive. The chemical code that triggers those changes can be deciphered and then duplicated to breed more vigorous, productive and resilient crops.

That’s the conclusion of a team of Penn State molecular plant geneticists that conducted the first-ever study of those reprogramming effects and discovered that “epigenetic reprogramming” code, which results in the expressing and over expressing of some genes and the silencing of others. Understanding and someday harnessing that reprogramming process, the researchers contend, will be critical to breeding crops that can tolerate weather extremes brought on by climate change.

“Plants can enter these new states—either really vigorous growth or, let’s say, hunkering down to withstand stress,” said team leader Sally Mackenzie, professor of plant science in the College of Agricultural Sciences and professor of biology in the Eberly College of Science. “In other words, we don’t have to cross breed to make it happen. We don’t need to add new genes because the plants actually go into that state, when properly prompted, on their own.”

In the study, recently published in Genome Biology, the researchers manipulated the MSH1 gene to trigger at least four distinct nongenetic states to impact plant stress response and growth vigor. Cross-comparing data from these four states, they identified particular gene targets of epigenetic change within the genome where they could locate and decode data relevant to plant-growth.

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Citizen Science Genetics, Breeding, Growth Pollinators, Molluscs and Other Invertebrates

Plant-insect Interaction

Boy’s discovery reveals highly complex plant-insect interaction: When eight-year-old Hugo Deans discovered a handful of BB-sized objects lying near an ant nest beneath a log in his backyard, he thought they were a type of seed. His father, Andrew Deans, professor of entomology at Penn State, however, knew immediately what they were—oak galls, or plant growths triggered by insects. What he didn’t realize right away was that the galls were part of an elaborate relationship among ants, wasps and oak trees, the discovery of which would turn a century of knowledge about plant-insect interactions on its head.

Many plant-insect interactions are well documented. For example, most “cynipid” wasp species have long been known to induce oak trees to produce protective galls—or growths—around their larvae to ensure the safety of their developing offspring. Additionally, certain plants—including bloodroot (Sanguinaria canadensis), a wildflower native to North America—produce edible appendages, called elaiosomes, on their seeds to attract ants, which then disperse the seeds by carrying them back to their nests.

This latter example is referred to as “myrmecochory”—or seed dispersal by ants. “In myrmecochory, ants get a little bit of nutrition when they eat the elaiosomes, and the plants get their seeds dispersed to an enemy-free space,” Deans explains. “The phenomenon was first documented over 100 years ago and is commonly taught to biology students as an example of a plant-insect interaction.”

The team’s new research—initiated by Hugo’s discovery of galls lying near an ant nest—revealed a much more complex type of myrmecochory, one that combined the wasp-oak gall interaction with the edible appendage-ant interaction. “First, we observed that, while these galls normally contain a fleshy pale-pink ‘cap,’ the galls near the ant nest did not have these caps, suggesting that maybe they were eaten by the ants,” says Deans. “Ultimately, this led us to discover that gall wasps are manipulating oaks to produce galls, and then taking another step and manipulating ants to retrieve the galls to their nests, where the wasp larvae may be protected from gall predators or receive other benefits. This multi-layered interaction is mind blowing.”

The team’s findings were published in the journal American Naturalist.