Silphium was an extinct Libyan plant renowned for contraception, medicine, and trade. Its disappearance remains a historical mystery, and scientists continue searching for surviving descendants. Roman leader Julius Caesar is said to have kept a stock of it in the treasury. Ancient writer Pliny the Elder says Rome’s Emperor Nero owned the last stalk of [...]Researchers have uncovered why a common and costly dental implant infection often resists antibiotics. Dental implants have helped tens of millions of people regain a full set of stable, functional teeth, something traditional dentures cannot provide. However, between 10% and 20% of implant recipients eventually develop peri-implantitis, a serious infection that damages the jawbone around [...]
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For decades, scientists have understood that plants can release volatile organic compounds—essentially airborne chemical signals—to attract the natural enemies of the things that eat them, like caterpillars. What we didn’t know was exactly how a plant translates the physical act of being eaten into a specific, predator-summoning distress signal.
“[One] thing we didn’t know is how the plant detects the caterpillar in the first place,” says Adam Steinbrenner, a biologist at the University of Washington. Now, after years of experimenting with common bean plants in the lab and in the agricultural fields of Oaxaca, Mexico, Steinbrenner’s team pinpointed a single immune receptor that orchestrates its anti-caterpillar defense system.
When an herbivorous insect like a caterpillar feeds on a plant, it introduces its saliva straight into the plant's damaged tissues. This saliva contains biological clues called HAMPs: herbivore-associated molecular patterns. One of the HAMPs molecules is a peptide called inceptin, and there’s an 11-amino acid fragment of inceptin named In11, as well. Both of them turn out to be a fragment of the ATP synthase found in chloroplasts—basically a piece of one of the plant’s own proteins. As the caterpillar ingests the leaf, its gut enzymes chop up the plant's cellular engines and their pieces, including In11, are regurgitated back onto the leaf’s surface, albeit at extremely small concentrations.
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Researchers from Okinawa Institute of Science and Technology and Japan Agency for Marine-Earth Science and Technology have identified how bacteria can adapt to toxic metals released from hydrothermal vents. The study focused on Nitratiruptor sp. SB155-2, a species of bacteria isolated from vents in the Okinawa Trough. The researchers found that bacteria use transporter proteins […]
The post Testing their mettle: How bacteria in deep-sea vents deal with toxic metal environments appeared first on Science Bulletin.
Superblooms are massive blooms of desert wildflowers. There isn’t an exact number of flowers required to make something a superbloom. But the word usually describes an above-average number of blossoms. These flowers create colorful carpets that blanket usually barren desert landscapes. They can even be seen from space!
Deserts are dry ecosystems that get less than 25 centimeters (10 inches) of precipitation a year. As a result, these environments often have very little plant life.
The few flowering plants that do grow in deserts live very short lives. They spring up after rainfalls and race through their life cycles in a few days or weeks before heat and drought wipe them out. Before they die, these plants produce lots of seeds. Those seeds can lie dormant in the soil for years or even decades, waiting for the right conditions to sprout.
This creates a buildup of seeds in the ground. So when deserts have an unusually wet year after many dry ones, the seeds sprout into a superbloom. This happens as long as it’s not too hot or windy for the flowers to grow.
For animals that eat wildflowers, such as desert tortoises and sphinx moth caterpillars, superblooms are quite a feast. For humans, the blooms make a beautiful spectacle. But it’s important for visitors to not step on the blossoms or pluck them from the ground. That way, they can seed the next flower extravaganza.
Because of climate change bringing record-breaking droughts and heatwaves, superblooms could become even rarer.
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The evolution of land plants about 450 million years ago altered many of Earth’s geologic processes, like weathering and erosion. Due to the lack of evidence for meandering rivers before then, past scientists hypothesized that plants could have caused straight rivers to meander. However, in recent decades, researchers have challenged this idea. They’ve suggested that plants could have changed rivers without causing them to meander.
To understand how vegetation changed rivers in the past, researchers recently studied 49 modern meandering rivers. They sorted these rivers into 3 categories – vegetated, unvegetated, and semi-vegetated – by analyzing color images taken of them from the air. They identified 18 vegetated rivers located in South America, 24 unvegetated rivers in the western United States, and 7 semi-vegetated rivers in China and the Eastern United States.
To examine the impact of plants on these rivers, the researchers quantified how much each river channel curves, known as its sinuosity. They used opposite banks of each river bend to find its center point, then, using digital maps, drew a line along the river’s trajectory at an equal distance between the bend center points. They used this line to calculate the angle between the river’s curve and the center point. This angle, called the migration angle, shows how a river bend relates to the river’s downstream direction. By measuring it, researchers can tell whether a river is developing more vertically or horizontally, and how sharp its bends are, either of which could be influenced by plants.
The researchers compared migration angles across each river system to determine how river bends varied between vegetated and unvegetated rivers. They found that vegetated rivers tend to deposit sediments in the river bend, leading to curvier bends that develop horizontally and widen over time. In contrast, unvegetated rivers deposit sediment downstream, which means the rivers bend less and have greater variability in bend width.
The question remained whether plants were the primary cause of these differences or whether other factors were at play. To resolve this, the researchers investigated 3 additional factors. The first was the natural fluctuations in water flow across a river system, called its flow variability. They found that during storms, flow variability caused river bends to move downstream in unvegetated rivers, but not in vegetated rivers. This result suggested that flow variability alone didn’t drive downstream migration, although it can directly impact vegetation.
The second variable the researchers analyzed was the amount of sediment a river can carry, or its sediment flux. They found that rivers carrying more sediment can erode more banks, also shifting river bends. However, rivers with more sediment but the same level of plant coverage had statistically similar bend angles. Thus, the researchers concluded that sediment flux alone can’t drive bend development, and that the changes were instead dependent on vegetation cover.
The third variable they analyzed was riverbank strength. The researchers observed rivers with strong banks, made of rock or compacted sediment, and weak banks, made of loose sediment. They observed no difference in river bends with the same vegetation cover but different bank strengths. The researchers concluded that bank strength is also not the primary driver of bend migration in vegetated or unvegetated rivers.
Of the 4 variables the researchers examined – flow variability, sediment flux, bank strength, and vegetation cover – vegetation cover consistently had the greatest impact on the appearance of meandering rivers. They concluded that meandering rivers could have existed before plants, but would have looked different. Like modern unvegetated rivers, ancient meandering rivers likely had lower-angle bends. As plants evolved and grew on river banks, the bends would have developed differently, becoming curvier like modern vegetated rivers. They suggested that understanding this process provides insight into life on Earth before plants evolved 450 million years ago.
The post How did land plants change rivers? appeared first on Sciworthy.
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