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Why aren't plants' roots as diverse as leaves?

Why aren't plants' roots as diverse as leaves?



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I have been doing some gardening recently and I suddenly realised that all plants have superficially identical non-woody roots of the same size from gigantic trees to small fruiting plants and vegetables. They are all white, no more than 1 mm across, long and flexible with no distinguishing marks. Only when the root start to become woody do they become different in appearance.

Leaves are very diverse even when they have just started to grow, i.e. before they have reached their full size. I can recognise many different plants from their smallest leaves alone but I wouldn't be able to differentiate plants by looking at their roots. So why aren't roots anywhere near as diverse as leaves?


To answer this type of question, we should start by defining 2 concepts: the functions of the root and the external condition that brought to a specific evolution. Evolution is a necessary process to all organisms, which evolve to optimize a specific function and to better adapt to the external conditions.

There are 3 main and common functions between all land plant's roots: fix plants to the soil; absorb water and minerals; establish specific relationships with other organisms, principally fungi and bacteria. The external conditions of roots (soil) are quite stable, even though, the different "physical" composition of soil, that is the quantity of sand, clay and rocks, change the physical appearance of size and proportion between the main and the lateral roots.Therefore it is plausible to say that it is not necessary to have a great variety in root's structure; since all roots must carry out same functions, all plant's root underwent a similar evolution.

For the leaves it is a bit different. Leaves must also carry out specific and common functions, as: exchange gas (CO2 and O2); contain photoreceptors to "absorb" light for photosynthesis. However, the external conditions of leaves are shortly and continuously changing and highly different (consider the vary regions of the world, as desert and rainforest) with reference to roots. Therefore each plants underwent evolution depending on these types of external conditions, so as to, of course, optimize their functions but at the same time protect themselves as much as possible. Consider, for example, the intensity of sun's radiation, which, if too strong, can destroy cellular structures, the quantity of CO2 in the air, or the high biodiversity of insects, which can carry diseases, ecc…

Interesting book about evolution is: J.C. Harmon, S. Freeman, "Evolutionary analysis", where it is given an idea of the type of evolution, different species, could undergo. (hope my english is not too bad)


I originally listed two reasons for the relative lack of diversity among roots - the substrate and roots' primary function, transporting water and nutrients. After giving it more thought, I've expanded the list to four reasons.

1. SUBSTRATE - Burrowing animals are far less diverse than animals that live aboveground; note the remarkable similarity between moles, golden moles and marsupial moles - all unrelated. The obvious reason is that they're adapted to living in soil. Roots are similarly constrained by their environment. It's hard to imagine a giant palm leaf growing underground.

2. UNIFORM ENVIRONMENT - Leaves experience light and dark, daily temperature fluctuations and even greater seasonal fluctuations. They may be pummeled by high winds, hail and fire. These variables may influence leaf evolution in many different ways. In contrast, roots grow in an environment that is always dark, relatively protected from wind, hail and fire and relatively stable temperature wise.

3. FUNCTION - Aside from anchoring plants, roots' primary function is transporting water and nutrients. The optimum shape for this is round, similar to the veins in our bodies and the plumbing in people's homes. Rectangular roots or roots shaped like maple leaves make no sense.

4. PREDATORS - A wide variety of animals feed on leaves, which may evolve defenses against predation. For example, a cactus' spines are modified leaves that are widely believed to serve as defenses against animals in search of a juicy cactus. In contrast, relatively few animals feed on roots. There are a few species that dig for roots, and some burrowing animals feed on roots, but virtually no wild primates or ungulates feed on roots.

In summary, leaves grow in an environment where they are less constrained and less protected by the surrounding substrate and are exposed to a far greater variety of environmental variables and predators.

As far as color goes, I don't see much difference; most roots are whitish or brownish, while most leaves are green. Of course, leaves of some species do change colors in the fall, when temperatures begin to decrease. But, once again, roots are relatively insulated from the cold, especially if the ground is covered with a blanket of snow.


Plant Evolution and Diversity - Plant Fossils

The tricky thing about studying evolution is that so many things happened in the past, and in some cases so long ago, we just can't know everything. But one solid piece of evidence for many studies is the fossil record. That's right, dinosaurs aren't the only fossils out there.

Plant fossils can be one of two forms: macrofossils, which are large enough to see with the naked eye and microfossils, which need a microscope to be visible. Macrofossils are usually wood, leaves, seeds, or roots that were fossilized. Microfossils are fossilized pollen.

Fossilized pollen may seem like a funny thing to go looking for, but if you think about it, it's actually a pretty bright idea. The gymnosperms that dominated the plant world before the rise of angiosperms were wind-pollinated, and so are some angiosperms. Wind pollinated plants release a lot of pollen, since the wind could carry the pollen anywhere before it finds another individual of the same species. In some areas, like lakes or riverbeds, tons and tons of pollen was laid down and fossilized, so we can get a really good idea of what plants used to grow there. Of course, pollen and plants change over time, so it is not always possible to identify the particular species, but we can get down to the genus in many cases.

Fossils are really old. Like, really really old. To know just how old they are, scientists can use a technique called radiometric dating, which uses the half-life of a known radioactive isotope to tell the age of a rock. Unfortunately, this process does not create Teenage Mutant Ninja Turtles.

Fossils can be really informative, and there is no other way we could know what plants looked like in the past. However, fossils do not form everywhere, so we don't have fossil evidence from every habitat all over the world. Water and layering of sediment is usually necessary for fossils to form, so fossils are often formed in rivers, lakes or estuaries, and they can be found in areas that were rivers, lakes or estuaries in the past.

We can recreate or at least imagine what ancient landscapes looked like because we have fossils from those times. Back in the Carboniferous period, about 300 million years ago, the world was warm and wet—quite tropical, in fact. It probably would have been a lovely time to set up a beach chair and bask in the sun, except that much of the land was swampy. Even though the descendants of early land plants that we have today are usually pretty small (mosses, ferns, and club mosses aren't exactly giants), there were actually large trees. The picture below shows what an landscape might have looked like 300 million years ago:


(Source)

Brain Snack

The oldest plant fossils are about 500 million years old and were found in Argentina.


More Great Resources to Read about Monocots vs Dicots

Monocots vs Dicots: A quick overview from Berkley.

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Written by Rob Nelson

Rob is an ecologist from the University of Hawaii. He is the co-creator and director of Untamed Science. His goal is to create videos and content that are entertaining, accurate, and educational. When he's not making science content, he races whitewater kayaks and works on Stone Age Man.


Stems vs roots

Copyright 1999, National Gardening Association.
All Rights Reserved.

Similarity: Both stems and roots contain vascular tissues (xylem and phloem), the circulatory system of the plant.

Difference: In herbaceous stems, the vascular tissues are contained in bundles these bundles sit relatively near the surface of the stem. In roots, the vascular tissues form a central core—a location where they're protected from the harsh activity of pushing through soil. (We are referring to young, non-woody tissues.)

Comparison of Stem and Root Cross-Sections

Similarity: Both stems and roots are able to initiate lateral growth: that is, to form "branches."

Difference: In stems, side branches arise from axillary buds. These buds are located at the nodes in the leaf axil (the point where the leaf attaches to the stem).

Lateral roots, on the other hand, arise from deep within the root's tissue, near the central core. Roots don't have nodes, and they don't have buds.

Role reversal
Though most stems are above ground, and most roots are underground, this isn’t always the case. Consider the following underground plant parts:

--potato tuber
--iris rhizome
--tulip bulb
--gladiolus corms

We may think of them as roots, and in many ways they perform the same functions as roots, but, technically speaking, these are all modified underground stems.

Have you ever noticed the little aerial roots sprouting from the stems of philodendrons and orchids? As you might have guessed, these are examples of above ground roots.


Why aren't plants' roots as diverse as leaves? - Biology

Plants are of different types. Plants is a living organism of the kind exemplified by trees, shrubs, herbs, grasses, ferns, and mosses, typically growing on a permanent site, absorbing water and inorganic substances through its roots, and synthesizing nutrients in its leaves by photosynthesis using the green pigment chlorophyll. Plants can be both aquatic and terrestrial. Plants are diverse, but parts of plants are same. Roots, stem and leaves are main parts of plants. These parts are modified according to an adaptation of plants.

Modification of Roots

Parts of plants below the soil is root. The color of roots is of white, grey and light yellow. Root are of two types:

According to adaptation plants, modifies its roots. Roots are modified for following purpose:

For storage of food

Let's take an example modification of radish, turnip and carrot for storage of food.

  1. Upper and lower parts of radish are thinner, but the middle part of the root is thicker in radish.
  2. In turnip, the upper part of turnip is round and broader but the lower part is narrower.
  3. In carrot, upper part is broader and the lower part is thinner and sharper like the pencil.

For mechanical support

Peepal tree has broad base in order to support the huge tree. Bamboo also has a broad base. Bamboo grows longer and it needs firm support which is provided by its broad base. Similarly, maize and sugarcane also has different kind of root to support the plant as maize and sugarcane.

For Vital function

Some plants modify its stem to absorb the food from another plant. Plants growing in the marshy region has its roots extended outside to support respiration. Some plants conduct photosynthesis through the roots. Aquatic plants like Hydrilla have the root that can store air to float in water.

Modification of stem

Part of the plant just above the ground is the stem. Branches, leaves and flowers emerge from the stem. Stem modifies itself according to their adaptation.

  1. Underground Modification:Potato stem is inside the ground which has a thick stem to store food. Similarly, onion and garlic also have a thick stem as it stores food.
  2. Sub-aerial Modification:Some plants have soft and weak stem. Stems of grass help in reproduction.
  3. Aerial Modification:Some stems act as leaves and stores food and water in their stems. Example: cactus. Some stems are like the thread. Some stem is like enrolled wood. Green stems make foods and stores.

Modification of leaf

Leaves emerge from the stem. Leaf helps in photosynthesis and respiration. Leaves are modified in different forms according to an adaptation of plants. Some plants tend to have huge tendrils. Tendrils are usually coiled. Some leaves are modified into thorns which decrease the rate of transpiration. Thorns also protect the plants. Some leaves are as dry as paper. Some carnivorous plants have leaves with bladder to trap insects.

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Pteridophytes

Pteridophtyes are a phylum of plants. They are the vascular plants (those having xylem and phloem tissues) that reproduce by releasing spores rather than seeds, and they include the highly diverse true ferns and other graceful, primarily forest-dwelling plants. There are about eleven thousand different species of pteridophytes, making them the most diverse land plants after the flowering plants (angiosperms). Pteridophytes may represent the closest living relatives (sister group) to the seed plants. (Seed plants include the angiosperms, the conifers, and a smaller assortment of other plants.)

As in seed plants, the greatest diversity of pteridophytes is found in the tropics, with only about six hundred species adapted for life in temperate climates. Species living today are relics of ancient lineages that once dominated

Pteridophytes range greatly in size. There are tiny floating ferns used as "green fertilizer" in rice paddies because they partner with bacteria that pull nitrogen from the air and ȯix" it in chemical compounds that other plants can use. In some tropical forests, the largest plants are tree ferns that can be up to 30 meters (100 feet) tall and have huge spreading leaves up to 4.5 meters (15 feet) in length. Pteridophytes also show a transition from simple to complex leaves. Some pteridophyte groups, including the club mosses and horsetails (classes Lycopodiopsida and Equisetopsida), have simple microphyllous leaves, featuring a single, unbranched vein and modest vascular supplies that do not cause breaks or gaps in the stem vasculature. The true ferns (class Filicopsida), however, have larger, more complex macrophyllous leaves whose veins are usually extensively branched, placing such large demands on the plant's vasculature that distinctive gaps form in the xylem and phloem of the stem.

All pteridophytes have a true alternation of generations, in which a dominant sporophyte generation produces spores through meiosis , and a free-living gametophyte generation forms gametes (egg and sperm) by mitosis . Ferns can be used to illustrate the life cycle stages common to all pteridophytes. Diploid (2n) fern sporophytes are familiar to most people and are often found as quiet accompaniments in floral arrangements. When mature, the undersides of fern leaves produce clusters of capsular structures called sporangia, within which meiosis forms the haploid (n) spores. These spores are released from the sporangia, often when dry wind currents cause the active snapping of the capsules, lofting the spores into the air.

Spores that are wind-borne to shady, moist habitats germinate and yield multicellular, but microscopic, gametophytes, the sexual stage of the life cycle. These short-lived, delicate plants mature and produce egg-forming archegonia and sperm-producing antheridia. When water is present, multi-flagellated sperm swim from mature antheridia, are chemically attracted to the necks of the archegonia, and fertilize the eggs. Although frequently bisexual (hermaphroditic), in most cases the sperm produced by a gametophyte cannot successfully fertilize its own eggs and must swim to archegonia on neighboring, genetically different gametophytes. The diploid zygotes , produced by the fusion of haploid egg and sperm, divide mitotically and differentiate into mature sporophytes, completing the life cycle.

Although most pteridophytes are homosporous (produce spores that are all the same size), a few groups are heterosporous with large megaspores and small microspores. The megaspores produce megagametophytes that only form eggs, and microspores only produce microgametophytes and sperm. Heterospory evolved independently in several groups of vascular plants, including all members of the orders Selaginellales and Isoëtales and those in a few fern groups (the families Marsileaceae and Salviniaceae of the class Filicopsida). The most successful origin of heterospory ultimately resulted in the great diversity of seed plants.

No pteridophytes are cultivated as crop plants, but the leaf buds (ȯiddleheads") of some ferns are commercially harvested and canned or frozen. Fern leaves used in floral arrangements are a major industry in Florida, and in some cultures tree fern stems are used to make elegant, naturally sculpted bowls. The contrasting colors of the vascular tissue in the stems and leaf bases of these plants create complex and pleasing designs. In the past, club moss spores provided the powder used to coat rubber gloves and prophylactics, and photographers used masses of these same spores as flash powder, since they could be easily and quickly ignited.


Types of Adaptations in Hydrophytes

Three types of adaptations occur in hydrophytes.

Ecological Adaptations

Roots

In hydrophytes, the major absorbing part, i.e. roots are the less significant structure. Its overall growth is either poorly developed, reduced or absent. The root’s accessory components like root cap and root hairs are generally absent in floating hydrophytes.

In the plant species like Lemna, Ecchorhnia species, root pocket is present instead of root cap whose function is to maintain the water balance. Wolffia and Utricularia are the plants that lacks root system, but Hydrilla comprises poorly developed roots. The emergent forms contain well-developed roots.

Stems

In submerged forms comprise an elongated, narrow, cushioned and flexible stem. The stems are wide, small, stoloniferous, narrow, and cushioned with extensive parenchyma. It floats horizontally in the free-floating hydrophytes, as in Azolla. In rooted floating hydrophytes, a stem functions as a rhizome or runner.

Leaves

Free-floating hydrophytes consist elongated, slender, flattened leaves. The leaf’s upper surface is coated with a waxy cuticle. Submerged hydrophytes contain leaves that are slender, translucent, elongated, fibrillar, straight and finely dissected.

In amphibious plants, the leaves are of two kinds (submerged and aerial leaves). The submerged leaves show resistant against potential damage by the water current and absorb dissolved carbon dioxide.

The leaves of emergent hydrophytes resemble the leaves of terrestrial plants. Aerial leaves are bulbous, lobed in structure and showing features similar to the mesophytic characters by having a wax coating on the upper leaf surface.

The waxy coating prevents the leaves of hydrophytes against wilting, physical damage, chemical injuries, blockage of stomata etc. The partly submerged plant possesses different patterns of leaves or shows heterophylly, like in Ranunculus aquatilis.

Physiological Adaptations

Shoot system: Stems and leaves participate in the cellular processes (like photosynthesis and respiration), and liberates gases (like oxygen and carbon dioxide), which eventually retain within the air cavities.

The hydrophyte plants could use gases like oxygen and carbon dioxide in the air cavities for the future cell activities. Petioles in floating hydrophytes have a huge tendency of regeneration, which is reasonably controlled by the auxins.

Protective layer: Mucilage cells make up the mucilage canals, which secrete a lubricating agent, i.e. mucilage to protect the plant body against friction, desiccation, decay and other stresses, by covering the entire plant body.

Food storage: Some hydrophytes (water lily) reserves food inside the rhizome.

Osmotic concentration: Hydrophytes possess a low osmotic concentration of the cell sap than the surrounding water.

Transpiration: It is absent in submerged plants, while floating and emergent hydrophytes go through high rate of water loss or transpiration.

Reproduction: The vegetative reproduction commonly occurs in hydrophytes by the propagation of the vegetative structures like runners, stolons, root-tubers etc.

Pollination and dispersal: Both pollination and dispersal of fruits occur by the agency of water. The dispersed seeds and fruits generally remain on the water surface, as they are light in weight.

Other properties: Processes like an exchange of water, nutrients and gases occur by the entire plant surface. Mucilage functions as a lubricating agent by surrounding the submerged parts of hydrophytes and protects them from epiphytes. An aerial part of hydrophyte bears hydathodes, which removes the additional water entering into the plant body via endosmosis.

Anatomical Adaptations

Epidermis

It is present as a thin or a single layer, which comprises parenchyma cells that are non-protective in function. The epidermis of the leaves include chloroplasts, which participate in the process of photosynthesis.

Mucilage encircles the epidermis of the submerged parts and protects the plant against decay. The hypodermis is either absent or poorly developed. The submerged parts of hydrophytes generally lacks cuticle but can be present as a thin layer on the aerial parts.

Stomata

The submerged parts lack stomata, but the upper surface of floating leaves carry stomata that is called “Epistomatous leaves”. Potamogeton is a hydrophyte consisting of non-functional stomata. The emergent hydrophytes consist of scattered stomata on all aerial parts of hydrophytes.

Aerenchyma

It refers to the air cavities found between the differentiated mesophylls, which allows the convenient diffusion of the gases. The diffused gases travel through the internal gas spaces of young leaves, then forced down to the root by the aid of water pressure through the aerenchyma cells of the stem. Older leaves do not support the pressure gradient, so the gases from the roots expel out through the leaves.

Cortex

Hydrophytes possess a highly-developed and thin-walled parenchymatous cortex, which helps the plants against mechanical stresses and also permits efficient gaseous exchange. The large air cavities occupy its major portion. Hydrophytes comprise starch granules as the primary reserve food material, which accumulate inside the cortex and pith.

Mechanical Tissue

Hydrophytic plants possess mechanical tissue (sclerenchyma and collenchyma). Only the aerial or terrestrial parts possess the mechanical tissues and the floating and submerged parts completely lack or contain poorly developed mechanical tissues. Cystoliths or sclereids of variable shapes are present in the tissues of leaves and other plant cells.

Vascular Tissue

Submerged hydrophytes have poorly-developed xylem and tracheids. In contrast, the amphibious plants contain well-developed xylem (towards the central region). Secondary growth in stems and roots does not occur in hydrophytes. In hydrophytes, the presence of endodermis and pericycle are distinct.

Mesophyll Cells

Hydrophytic plants possess undifferentiated mesophyll cells in the submerged leaves and differentiated mesophylls (palisade and spongy mesophylls) with the well-developed air cavities in both the floating and emergent hydrophytic leaves.

Conclusion

Therefore, we can conclude that all the living creatures undergo specific changes according to the changing environmental conditions where they have to live in, whether it is aquatic or terrestrial. Hence, the hydrophytic plants also go through a few modifications in their morphology and physiology to sustain life in an aquatic environment.


Challenges of Terrestrial Environments: Desiccation and Upright Growth

The major challenge for early plants first migrating onto land was the lack of water. In an aquatic environment, desiccation is generally not a problem and there is no need for any protective covering to prevent water loss. Lacking any protection from the dry terrestrial environment, early plants probably dried out very quickly and would have been limited to very moist environments.

The ancestors of early plants were dependent on water, not only to maintain their moisture content but also for structural support. The buoyancy of water supports upright growth of giant marine seaweeds (e.g., kelp, Fig. 6) Consider the seaweeds that are often found washed up on the beach. Although these algae are no longer alive, when held beneath the water their upright form is restored. In a terrestrial environment, the surrounding media is air rather than water. Air does not provide any support for upright growth. The transition to land required changes in structural features, and, as will be discussed later in this tutorial, adaptations for structural support are key features used in plant classification.


Figure 6. Kelp forest off California coast (http://bio.research.ucsc.edu/people/carr/nereo-lit.htm)


The World beneath our Feet

The first indication that bacteria in the soil influence the health of plants came in the late 1800s when Dutch scientist, Martinus Beijerinck, discovered Bacterium radicicola living in the roots of legume plants. Beijerinck found that this bacterial species converts atmospheric nitrogen into a form bioavailable to the plant in a process he called nitrogen fixation. These bacteria also do more than serve as a source of nitrogen for the plants that they inhabit.

In 1904, the German scientist Lorenz Hiltner introduced the term &ldquorhizosphere&rdquo, based on Beijerinck&rsquos findings and the discovery of several other nitrogen fixing, soil-dwelling bacteria. He defined the rhizosphere as the region surrounding a plant&rsquos roots where microbes live and contribute to the health of the plant. He hypothesized that these microbes are recruited by nutrients released from the plant&rsquos roots. Extensive research since Hiltner&rsquos introduction of the rhizosphere has confirmed his hypothesis that it supports a dense and robust microbial population. In fact, one study found up to 10 times more bacteria (around 10 10 bacteria per gram of soil) dwell in the regions near the roots of wild oats compared with the bulk soil outside of the rhizosphere. These populations of rhizobacteria (rhizosphere-dwelling bacteria) are quite diverse as well, with estimates that up to 52,000 different taxa are represented in a single rhizosphere.

As Hiltner hypothesized, plants also influence bacteria within and attract bacteria to their rhizosphere by releasing chemicals and nutrients from their roots, known as rhizodeposits. Each plant releases unique rhizodeposits, so the rhizosphere of one plant is often comprised of different groups of bacteria than other plants.


When we think of the word “plants” we typically picture trees, bushes, grasses, and ferns – so-called “vascular plants” because of their full systems of leaves, stems, and roots. However, the plant kingdom also includes mosses, liverworts, and hornworts, simpler plants that lack these water-transporting structures.

Photos courtesy of Scott Kinmartin and Andrew Fogg via Flickr.

A defining characteristic of plants is their ability to produce energy through photosynthesis. Through this process, plants capture the sun’s energy and use it to fuel chemical reactions that convert carbon dioxide and water into oxygen and energy-containing carbohydrates (sucrose, glucose, or starch).

Plants may reproduce sexually by flowering and producing seeds, or through spore production. They also reproduce asexually through budding, bulb formation, and other types of vegetative reproduction.

Even though most algae and fungi are no longer classified within the plant kingdom, they are often still included in discussions of plant life. Algae include microscopic, single-celled, and multicellular photosynthetic organisms such as seaweeds and green, red, and brown algae. They lack the structures that characterize vascular and nonvascular plants and are classified in the kingdom Protista.

Red algae. Thought algae look like plants, they are not classified in the plant kingdom. Photo courtesy of Fernando Ruiz Altamirano via Flickr.

Fungi do not produce energy through photosynthesis but instead obtain food by breaking down and absorbing surrounding materials. While previously classified with plants, fungi are now considered more similar to animals and are in a kingdom of their own.

Fungi. Photo courtesy of DonGato, Flickr.

Many fungi reproduce with fruiting bodies, a spore-bearing structure produced above soil or a food source. Mushrooms are a well-known example of fruiting bodies.

Lichens are a third group that, while often included in discussions of plants, is not classified in the plant kingdom. Lichens are a symbiotic association of a fungus and an alga. The fungus provides water and minerals from the growing surface, while the alga produces energy for both organisms through photosynthesis. Lichens compete with plants for sunlight, but their small size and slow growth allow them to thrive in places where plants have difficulty surviving.

Lichens are a symbiotic association of a fungus and an alga. They are not plants. Photos courtesy of Trapac and brewbooks via Flickr.

Despite cold temperatures, permafrost, and short growing seasons, vascular and nonvascular plants, algae, fungi, and lichens are found in both the Arctic and Antarctic regions. Learn more about these hardy species and the adaptations that enable them to survive in such harsh environments.

ARCTIC PLANTS

Approximately 1,700 species of plants live on the Arctic tundra, including flowering plants, dwarf shrubs, herbs, grasses, mosses, and lichens. The tundra is characterized by permafrost, a layer of soil and partially decomposed organic matter that is frozen year-round. Only a thin layer of soil, called the active layer, thaws and refreezes each year. This makes shallow root systems a necessity and prevents larger plants such as trees from growing in the Arctic. (The cold climate and short growing season also prevent tree growth. Trees need a certain amount of days above 50 degrees F, 10 degrees C, to complete their annual growth cycle.)

Tundra vegetation is characterized by small plants (typically only centimeters tall) growing close together and close to the ground. A few of the many species include:

Lichens grow in mats on the ground and on rocks across the Arctic. Lichens provide an important food source for caribou in the winter.

Reindeer lichen (also known as Caribou moss) is found across the Arctic. Its name comes from its resemblance of tiny antlers. Photo courtesy of Gerry Atwell, U.S. Department of Fish and Wildlife Services.

ANTARCTIC PLANTS

There are only two native vascular plants in Antarctica: Antarctic hair grass and Antarctic pearlwort. These species are found in small clumps near the shore of the west coast of the Antarctic Peninsula, where temperatures are milder and there is more precipitation.

/> Antarctic hair grass (Copyright 2004 Gerald and Buff Corsi, California Academy of Sciences) and Antarctic pearlwort (Copyright 2007 Gerald and Buff Corsi, California Academy of Sciences).

There are approximately 300 types of moss found in colonies, over 300 nonmarine algae species, and approximately 150 species of lichens. Lichens can tolerate very cold temperatures, and thus can live where true plants cannot. Lack of water, not cold temperatures, is the largest concern, and lichens deal with this problem by living in cracks between rocks.

ADAPTATIONS FOR A POLAR ENVIRONMENT

Similar adaptations help plants, algae, fungi, and lichens survive in both the Arctic and Antarctic.

First, the size of plants and their structures make survival possible. Small plants and shallow root systems compensate for the thin layer of soil, and small leaves minimize the amount of water lost through the leaf surface.

Plants also grow close to the ground and to each other, a strategy that helps to resist the effects of cold weather and reduce damage caused by wind-blown snow and ice particles. Fuzzy coverings on stems, leaves, and buds and woolly seed covers provide additional protection from the wind.

Plants have also adapted to the long winters and short, intense polar summers. Many Arctic species can grow under a layer of snow, and virtually all polar plants are able to photosynthesize in extremely cold temperatures. During the short polar summer, plants use the long hours of sunlight to quickly develop and produce flowers and seeds. Flowers of some plants are cup-shaped and direct the sun’s rays toward the center of the flower. Dark-colored plants absorb more of the sun’s energy.

In addition, many species are perennials, growing and blooming during the summer, dying back in the winter, and returning the following spring from their root-stock. This allows the plants to direct less energy into seed production. Some species do not produce seeds at all, reproducing asexually through root growth.

ADAPTING TO A CHANGING CLIMATE

The polar regions have been of great concern as the Earth’s climate warms. While we’ve heard about the declining sea ice and its negative impact on marine wildlife, there’s evidence to suggest that Arctic plants may be better able to adapt to a warming world. Studies of nine flowering plant species from Svalbard, Norway, suggest that Arctic plants are able to shift long distances (via wind, floating sea ice, and birds) and follow the climate conditions for which they are best adapted. Wide dispersal of seeds and plant fragments might ensure survival of species as climate conditions change. While encouraging, this data does not necessarily extend to Antarctic species or species in the temperate regions.

LINKS

Tundra Plants
Detailed information about eight plant species that are found on the Arctic tundra.

Plants of Antarctica
An overview of the species found in Antarctica.

Life on Antarctica: Plants
Information about the vascular plants, lichens, mosses, algae, and fungi found in Antarctica.

Grow Low, Grow Fast, Hold On!
An overview of Arctic plant adaptations.

NATIONAL SCIENCE EDUCATION STANDARDS: SCIENCE CONTENT STANDARDS

The entire National Science Education Standards document can be read online or downloaded for free from the National Academies Press web site. The following excerpt was taken from Chapter 6.

A study of plants aligns with the Life Science content standards of the National Science Education Standards. In grades K-4, students focus on the characteristics and life cycles of organisms and the way in which organisms live in their environments. Students in grades 5-8 expand on this understanding by focusing on populations, communities of species, and the ways they interact with each other and with their environment.

Teaching about plants can meet a wide variety of fundamental concepts and principles, including:

  • The Characteristics of Organisms
  • Life Cycles of Organisms
  • Organisms and Their Environments
  • Reproduction and Heredity
  • Regulation and Behavior
  • Populations and Ecosystems
  • Diversity and Adaptations of Organisms

This article was written by Jessica Fries-Gaither. For more information, see the Contributors page. Email Kimberly Lightle, Principal Investigator, with any questions about the content of this site.

Copyright March 2009 – The Ohio State University. This material is based upon work supported by the National Science Foundation under Grant No. 0733024. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. This work is licensed under an Attribution-ShareAlike 3.0 Unported Creative Commons license.