Many trees lose their leaves in the fall to conserve resources for future blooming rather than spending them on keeping leaves alive in the wind and cold of winter.

During the fall, shorter days trigger cells in leaves to produce less chlorophyll, a green pigment that is typically present in sufficient concentrations to mask other pigments, such as yellow and orange.

Most cells undergo programmed, controlled death

In the average adult human, apoptosis occurs in 50 billion to 70 billion cells daily when proteins managing a cell's life cycle send signals that the cell is damaged, causing it to break apart into smaller pieces that are consumed by white blood cells. The consumption prevents damage from spreading via cell division.

Wind helps trees develop resistance to collapse

Scientists at Biosphere 2 found that trees grew faster in the facility than those in the wild but collapsed more quickly when replanted outdoors. Researchers uncovered that trees build resistance when pushed and pulled due to wind stress, strengthening their foundational root systems.

Biosphere 2 revealed limitations in maintaining wildlife in unfamiliar environments

Trees appeared to become weak and more prone to breaking because a lack of wind caused them to no longer need to develop stress wood. The extinction of pollinators—potentially due to an explosion in the population of longhorn crazy ants—was also unexpected.

Plants use physical and chemical defenses to protect themselves

Tree bark is difficult to chew and resistant to pathogens, while the waxy cuticle on the surface of leaves deters insects and microbes. Some plants possess thorns, spines, and prickles to discourage predators. Plant cells can also produce antimicrobial toxins or release compounds to alert parasitic wasps to lay eggs in attacking insects.

How trees transport water from roots to leaves

Trees move water to their extremities via a deft system starting from the roots to the leaves. See how it works in this short video breaking down the process in a Douglas fir.

Keystone species with average lifespans exceeding a century, oak trees support more organisms than any other North American tree genus by providing ecosystems with pollen, shelter, and nutrient-rich acorns.

Do trees feel pain?

Trees don’t have nerves or brains. But when they’re wounded, they send underground and airborne warnings to other trees.

Lightning may kill as many as 320 million trees each year

Ignoring the effects of tree loss resulting from lightning-induced wildfires, researchers at the Technical University of Munich developed a quantitative model to estimate the loss of these organisms due to cloud-to-ground strikes, based on global lightning data and forest structure. They expect the estimate to rise due to increased strikes resulting from climate change.

The three categories of photosynthesis, which each help plants survive in different environments

In the vast majority of plants, C3 photosynthesis produces three-carbon intermediate molecules in the Calvin cycle within the cells of leaves. Plants in hot, dry climates use C4 photosynthesis across two types of cells to produce four-carbon molecules before the Calvin cycle. Plants in drought conditions use CAM to store carbon dioxide as an acid at night, minimizing water loss.

One theory claims the retinae of SAD patients may fail to adjust to less light in winter

Most people’s eyes become more sensitive to light in the winter months, but some do not. This failure to adjust causes ripple effects on those individuals’ biological clocks. This Ted-ED video provides a clear, brief, narrative explanation of the condition in six minutes.

Visualize the purpose of stomata in photosynthesis

These openings on the underside of leaves can be opened and closed by specialized guard cells to regulate the movement of carbon dioxide into and oxygen out of cells, thus impacting the rate of photosynthesis. At night, when the light-dependent reactions in photosynthesis are not possible, the stomata close to prevent the plant from losing water through transpiration.

Climate change is disrupting maple syrup by shortening its production season

The number of unusually warm winter days in parts of Maine has increased significantly over the past few decades, stressing maple trees into shifted sap flows and leaving producers with less consistent outputs.

Over 200 known species hibernate, allowing them to lie dormant and survive harsh periods when water and food become scarce, such as frigid winter months or scorching summer periods.

While most cells possess DNA, red blood cells destroy their nuclei to maximize the amount of oxygen they carry and more easily alter their shape to fit through narrow blood capillaries.

Tree rings can reveal centuries of environmental change and natural events

The width and shape of tree rings reflect yearly growth conditions like rainfall or snowfall. Scars in the rings can record disruptions such as fires, avalanches, or earthquakes, explaining when and how those events occurred.

'Watermelon snow'—patches of pink, orange, and red in snow—is the result of extremophilic green algae that thrive in extremely frigid conditions and take the shape of red spheres in winter.

A Death Valley shrub optimizes its cells' organelles to photosynthesize in extreme heat

Examining the cellular structure of the plant under heat, scientists observed the formation of novel, cup-shaped chloroplasts and mitochondrial relocation, which shifted the plant's optimal photosynthesis temperature to 45 degrees Celsius (113 degrees Fahrenheit) as it tripled in mass over 10 days. Engineering these mechanisms in crops may help optimize them for hotter environments.

The complexity of classifying a tree

It may seem obvious to us when we see a tree, but very specific characteristics cause scientists to distinguish trees from other types of plants. This video provides a visual and verbal explanation of distinctions that separate trees from other plants like shrubs or herbs. See a scientific breakdown of these traits.

This year's first leaf and first bloom in the US, mapped

Spring tends to arrive within a range of dates in the contiguous US. See a map illustrating the most recent year's first leaf and first bloom in relation to historical averages to see how early or late the season arrived.

A day in the life of a leafcutter ant

Among the fascinating world of insects, leafcutter ants form some of the most complex and dynamic social ecosystems. All part of an effort to keep a colony alive, worker ants toil tirelessly, dragging bits of leaves and vegetation back to their...

How freeze-drying leaves food with less than 4% of its original water content

In specialized equipment, foods are brought down to temperatures below freezing before a vacuum pump removes the air from the container, lowering the pressure around the food and the boiling temperature of water. Heaters beneath the food slowly raise its temperature above the now-reduced boiling point, causing the water to go from a frozen to a gaseous state.

View colorful flowers that grow on cacti and succulents, popular xerophilic organisms

These dry-loving organisms are able to retain the water they need to grow and reproduce in deserts and arid grasslands through a suite of adaptations, including thick, fleshy stems that store abundant water, a waxy coating that helps prevent water loss, and an uncommon form of photosynthesis that loses less water.

View a fall foliage prediction map to estimate the progressive change in the color of leaves throughout the US from September to mid-November.

Fig trees are considered keystone species because they provide year-round habitat and fruit, which are eaten by an estimated 1,300 species of birds and mammals worldwide.

Lack of sunlight during Arctic winters can fuel a winter slump and a circadian disconnect.

Transpiration drives water movement through a plant’s vascular system

Water evaporates from the leaves, creating tension that pulls more water upward from the roots through the xylem—the equivalent of plant blood vessels. This process is supported by water molecules sticking to each other (cohesion) and xylem walls (adhesion).

The ritual burns of California forests

Many ecosystems around the world have adapted to regularly occurring wildfires. Some human cultures saw the advantage of such fires and integrated them into their community rituals. Learn about similar tribal traditions looking to better manage California's forests today.

To survive underwater hibernation, some freshwater turtles perform cloacal breathing—blood vessels absorb dissolved oxygen from water drawn into the organism's cloaca, or rear orifice.

Adapt or freeze: How plants and animals thrive in the Arctic Tundra

This article explores the fascinating ways both animals and plants adapt to survive in Alaska's arctic tundra, an ecosystem marked by its extreme weather. Most tundra plants are perennials with short growing seasons that focus on gathering and...

There are over 20,000 trees on the National Mall

Nearly 4,000 of the Mall's trees are cherry trees, all maintained by a small National Park Service arborist team that provides year-round, science-based care to address soil compaction, root damage, and heavy visitor traffic.

Butterfly populations have declined by 22% from 2000 to 2020

Research suggests that one in every five butterflies is lost due to pesticide use, habitat loss, and climate change. Playing a vital role in pollination, their declining populations threaten plant reproduction and the health of ecosystems.

Grief rewires the human brain

The human brain handles stress and emotional traumas similarly. In response to the emotional stress of a situation like the death of a loved one, divorce, or abuse, the brain may strengthen or weaken connections between nerves to form new neural connections. Over time, chronic stress can diminish brainpower, reducing overall nerve growth and memory to shift resources to enable elevated fear responses and enable humans to survive.

While invasive species typically harm ecosystems by outcompeting native organisms for resources, some provide unexpected benefits, including new shelters, nesting habitats, and reduced environmental heat stress.

Necrosis is the unplanned death of cells and the tissue they comprise

If cells die prematurely due to a lack of blood flow, injury, or disease, they and their organelles can swell, leading to rupture of the surrounding cell membrane. This releases the cell's contents into the surrounding tissue, causing inflammation and damage to neighboring cells.

Watch a time-lapse from space of photosynthesis across Earth

Using NASA satellite imagery, carbon absorption can be tracked and serves as a proxy for photosynthetic activity on land and in the oceans. Over the course of a year, seasonal changes can be observed as plants become dormant in the fall and active again in the spring.

Symptoms of DNA loss may mimic those seen in mushroom poisoning or chemotherapy

Although no organism has ever lost all its DNA, the destroying angel mushroom contains amatoxin, which disrupts DNA transcription and is known to cause death via liver and kidney failure in three days. Doxorubicin, which tangles DNA to disrupt cellular replication, compromises a person's immune system.

Appropriate timing of land management techniques can help support pollinators

The mowing, grazing, and burning practices used to maintain land should be tailored to the life cycles and needs of native pollinators, particularly those of rare or endangered species. For example, mowing is recommended in the fall or winter when flowers are not in bloom.

US honeybee colony loss remains a concern, despite rebounding from the mid-2000s CCD

In the winter of 2006-07, worker honeybees began mysteriously disappearing from hives—a phenomenon known as colony collapse disorder—triggering the loss of as many as 90% of hives. The lack of dead bees found near hives and the declining prevalence of CCD since then have made finding a single cause challenging.

Stem cells can reboot the ability of cells to repair themselves

Stem cells—special cells that can self-renew and evolve into new cell types—may provide a path to address aging. Instead of repairing aging cells, stem cells can replace a cell's "repair kit," effectively rebooting the internal processes of tissues to a more youthful state.

Even in nature reserves, climate change is driving rapid ecological collapse

Studies show a dramatic decline in insect populations, resulting in cascading global biodiversity losses across non-insect species. The balances in tropical ecosystems are the most affected by climate change.

How flowering plants took over the world

Flowering plants are relatively young in the evolutionary scheme of things, only arriving after the dinosaurs had already been wiped out. Their evolution has long puzzled scientists, but recent research indicates their success is due to smaller,...

The ginkgo tree is a living fossil that has not changed in over 200 million years

Having outlived the dinosaurs, the tree has no living relatives as the only surviving species of the genus Ginkgo. Its growth in undisturbed environments, pollution resistance, and foul-smelling seeds may have contributed to its survivability.

Aging results from the cumulative breakdown of cellular and tissue processes

A cumulative breakdown of cellular and tissue processes combines to result in decreased organ function, disrupting the systems driving normal human physiology. This five-minute video provides a primer on the subject, complete with a discussion of risk factors, cellular changes, and potential future treatments in the fight against aging.

How greenhouse gases and climate change impact the efficiency of photosynthesis

A review in the Journal of Experimental Botany found that higher temperatures reduce the efficiency of enzymes involved in photosynthesis and impair a plant's ability to control water loss and regulate carbon dioxide uptake. While increased carbon dioxide levels are understood to accelerate plant growth by boosting photosynthesis, researchers suggest these effects more than offset the potential gain.

Understanding the role of photosynthesis as a sink within the carbon cycle

Photosynthetic organisms are net carbon absorbers, pulling carbon dioxide from the atmosphere and storing it in organic compounds and within soil. Approximately one-third of humanity's carbon emissions are stored by these organisms.

Scientists testing how climate change affected plants found in a yearslong simulation study that poison ivy grew 70% faster than it did without extra carbon dioxide.

Imagining if humans could perform photosynthesis and how it would change our anatomy

Since chloroplasts reflect green light, becoming photosynthetic would give our skin a green appearance. Because photosynthesis has efficiencies of only 5% to 9%, and humans burn 2,000 Calories daily compared to about 200 burned by a tree, becoming photosynthetic would also require us to adopt a less active, sun-filled lifestyle.

Sleep deprivation leads to the buildup of dangerous molecules in the gut.

Cells cannot grow forever due to escalating inefficiency in transporting chemicals

As cells get larger, their volume grows much faster than the surface area through which nutrients and waste products pass, creating a bottleneck that eventually causes cells to die. This forces nearly all organisms visible to the naked eye to comprise enormous numbers of smaller cells, such as the approximately 30 trillion found in the average adult human.