Buzz
In the biological world, plant enthusiasts often go unnoticed and are sometimes the subject of ridicule. Sure, plants might not have the same flash as majestic whales, ancient dinosaurs, or creatures so small they can kill you with a single bite, but they still hold their own. (And don’t even get me started on rocks.)
Plants often have secrets that aren’t immediately obvious, and studying them can be a greater challenge than studying animals. My hope is that this list will help everyone reading it discover the incredible world of plants.
10. CAM and C4 Plants
CAM and C4 plants, like succulents and cacti, are desert survivors. CAM stands for ‘Crassulacean Acid Metabolism,’ and C4 refers to the use of four carbon molecules in their metabolism. These plants have adapted to harsh, dry environments by modifying their processes to conserve water. While most plants open their stomata during the day to let carbon dioxide in for photosynthesis, CAMs and C4s have figured out a different way to thrive in such hot, arid conditions.
CAM and C4 plants keep their stomata shut during the day to prevent water loss. However, this leads to carbon dioxide binding to the wrong protein, causing sugar consumption instead of production. This issue, known as photorespiration, is cleverly avoided by these plants by opening their stomata at night. This allows carbon dioxide to attach to a different protein called phosphoenolpyruvate (PEP). With this process, CO2 binds effectively to form the four-carbon compound oxaloacetate (OAA), enabling desert plants to gather carbon dioxide overnight and use it for metabolism during the day.
9. Phloem and Xylem
‘Phloem’ and ‘xylem’ are technical terms for the cells that help distribute nutrients throughout vascular plants. These cells are also the reason vascular plants can grow so much larger than nonvascular plants. Xylem is in charge of transporting liquid from the roots all the way up to the leaves at the top. These cells are rigid and form the structure of wood, allowing the plant to grow tall without drooping or wilting.
Phloem is responsible for transporting nutrients, or ‘food,’ throughout the plant, though it lacks the rigidity and structure of xylem. To facilitate this transport, the xylem and phloem form tubelike structures up the stem, with the xylem in the center surrounded by phloem. Specialized companion cells allow water and sugars to move from cell to cell through small openings as needed.
8. Tropical Pitcher Plant
The tropical pitcher plant, a lesser-known carnivorous cousin of the Venus flytrap, has pitcher-shaped flowers with ultra-slick waxy walls and sweet nectar at the bottom, all capped with a lid. There are two types: the highland and lowland varieties. Both are found in the tropics in areas with constant humidity, but the highland variety is more common and has a tubelike shape, while the lowland variety has a broader, more typical flower shape on top of its pitcher.
Known for capturing small insects, the pitcher plant attracts its prey with its sweet nectar. Once inside, the creature struggles to escape while digestive enzymes in the liquid begin breaking it down. While insects are the usual prey, tropical pitcher plants have been known to consume entire rats! Their size allows them to trap even larger creatures, including clever rats.
7. Gravitropism
Gravitropism is a remarkable ability plants possess: the power to defy gravity. Normally, plants grow upward to capture sunlight for photosynthesis. However, when light is limited, they can grow in any direction, even upside down, in their search for it. In just a few hours, plants can shift their growth direction when sunlight is reduced. How do they do this so quickly? Their sophisticated system for detecting direction and gravity is the key.
At the top of the plant, known as the meristem, are specialized cells called statocytes that are sensitive to gravity, helping the plant determine which way it’s oriented. When these cells detect light, the plant adjusts its growth accordingly. Experiments show that plants without the meristem lose this ability, demonstrating the complexity and sophistication of plant evolution. Who needs eyes when you’ve got this system?
6. Accessory Pigments
We’re all familiar with chlorophyll, the green pigment in plants that plays a vital role in photosynthesis. However, even though many plants are green, they can come in a variety of colors and contain different pigments. Plants also possess accessory pigments, which are adapted to absorb various wavelengths of light, enhancing their absorption efficiency. The broader the spectrum of light a plant can absorb, the more sugars it can ultimately produce. These pigments can absorb nearly every color, as seen in the various types of algae:
Algae are classified into three main types: cyanobacteria (blue-green algae), rhodophytes (red algae), and ochrophytes (brown algae). In the ocean, light fades quickly with depth, complicating photosynthesis. As a result, accessory pigments are crucial for survival, and algae have evolved to absorb specific light colors based on their depth. Red light only penetrates shallow waters, so red algae often reside near the surface. On the other hand, blue light can reach deeper into the ocean, enabling blue-green algae to thrive in those depths. Despite red light’s lower absorption efficiency in the deep blue ocean, red algae’s ability to absorb it gives them an advantage over blue-green algae, which are more abundant.
5. The Most Abundant Protein in the World
Plants are home to what many consider the world’s most abundant protein. Ribulose-1,5-bisphosphate carboxylase oxygenase, or ‘RuBisCo,’ plays a crucial role in photosynthesis. Given the vast number of photosynthetic organisms scattered across the globe, it’s easy to see why RuBisCO is so prevalent. During photosynthesis, it binds with carbon dioxide, converting it from an inorganic to an organic state in a single step. RuBisCO remains unique as the only enzyme on Earth capable of doing this. When CO₂ attaches to RuBisCO, it forms an unstable six-carbon molecule that quickly breaks down into two 3-phosphoglycerate (3-PGA) molecules, which can then be used to produce sugars.
For CAM and C4 plants, RuBisCO can pose a problem. It becomes too efficient and can cause water loss, which is why these plants deactivate it. However, for most plants, RuBisCO is highly active during the day to maximize energy production. It’s incredibly effective, metabolizing four carbon dioxide molecules for every one oxygen molecule—quite an achievement when you consider that oxygen molecules are five times more abundant than carbon dioxide in the atmosphere.
4. Zooxanthellae
Zooxanthellae might sound strange, but it refers to a type of photosynthetic algae that lives inside coral reefs. These algae and the corals share a symbiotic relationship—corals offer a habitat for the zooxanthellae, while the algae provide essential nutrients through photosynthesis. The zooxanthellae produce oxygen, sugar, and amino acids for the coral, while helping to process harmful waste products, enabling the coral to synthesize fats and proteins. Surprisingly, the most beautiful oceans, home to the most vibrant coral reefs, are often the least productive waters. Clearer waters typically have fewer algae and bacteria, resulting in reduced growth, which in turn gives the water its clear appearance.
Zooxanthellae and corals depend on one another for survival in nutrient-poor, crystal-clear waters by maintaining a precise nutrient cycle. The clarity of the water actually benefits the algae, as it allows them to absorb light more effectively. However, a significant challenge to this finely tuned process is coral bleaching. When water quality deteriorates due to pollution or acidification, corals become stressed and expel their photosynthetic companions. This causes the corals to lose their color, taking on a “bleached” appearance. Once this occurs, the likelihood of survival for both the coral and the algae becomes very low. Bleached reefs are often unhealthy, leading larger species, like fish, to relocate to healthier areas, leaving behind a once-thriving ecosystem.
3. Ethylene
Ethylene is a gas released by fruits that triggers the ripening process. While we cannot see or smell it, this subtle gas plays a significant role in the ripening of fruits. Apples and pears, for example, release ethylene, while smaller fruits like berries don’t typically need to undergo ripening in the same way. The gas is believed to be associated with aging, which is why it initiates the ripening process. Once one fruit starts emitting ethylene, it encourages nearby fruits to produce the gas as well, speeding up their ripening. For this reason, it’s advisable to store fruits together to help them ripen faster.
Ethylene has also been harnessed industrially to assist farmers in accelerating crop production. It is commonly used on tomatoes to hasten their ripening process. However, excessive ethylene exposure can cause fruits to ripen too quickly, leading to overripeness and rot, and can even harm the plants, causing leaves and flowers to yellow or drop off. Despite these risks, ethylene remains a fascinating natural adaptation in plants, playing a key role in producing ripe and tasty fruit around the world.
2. Reducing Water Loss
While we’ve already discussed the unique adaptations of CAM and C4 plants to minimize water and energy loss, it’s not just these plants that face this challenge. Every plant has evolved mechanisms to conserve water in order to survive. Common adaptations include the development of waxy leaves, the strategic use of stomata, and guard cells. Guard cells encircle the stomata and regulate their opening and closing. When the guard cells are inactive, they are limp, causing the stoma to remain shut. When the guard cells become more rigid or 'flexed,' the stoma opens to allow gas exchange.
Guard cells operate in a manner similar to diffusion. Their opening occurs when there is a higher concentration of potassium ions inside the cells. This triggers the guard cells to take in water, and as the ion concentration levels out, the cells become limp, leading to the closing of the stomata. When the stomata are open, carbon dioxide enters the plant, facilitating photosynthesis. This process works in harmony, and at night, when the stomata close, the plant is able to conserve the water and energy it has accumulated during the day.
1. True Plants
Earlier, this list about plants mentioned algae—and it wasn't entirely honest. Algae and kelp, though often referred to as plants, don't actually qualify as 'true plants.' While they are much closer to plants than to animals, they belong to a distinct scientific category. The key difference lies in their morphology, even though their ability to photosynthesize is what frequently causes them to be grouped with plants.
What sets them apart? The most significant difference is that they lack true roots, stems, or leaves. For example, giant kelp may look like it has these structures, but they're actually quite different. Kelp doesn't have roots, but instead uses a holdfast, which anchors it to rocky surfaces, preventing it from being swept away by powerful waves or currents. Kelp's 'leaves' are called blades, and they differ from plant leaves in that they can sustain themselves. Each cell in a blade of kelp can independently supply its nutrients, so the kelp doesn't require a vascular system. The stipe, resembling a stem, lacks vascular features like phloem or xylem to transport water and nutrients. It simply provides structural support, allowing the blades to extend upward and capture sunlight at the water's surface.
