Plant Adaptations

4th Grade Living Systems

By Brandi Crouch

In drier, temperate deciduous forests a thick bark helps to limit moisture evaporation from the tree’s trunk.

Tropical rainforests have high humidity, and most trees have a thin, smooth bark.

This is probably because the trees to not need to protect against dryer conditions.

The smoothness of the bark may also make it difficult for other plants to grow on their surface.

Lianas are climbing woody vines that drape rainforest trees. They have adapted to life in the rainforest by having their roots in the ground and climbing high into the tree canopy to reach available sunlight.

Epiphytes are plants that live on the surface of other plants, especially the trunk and branches.

They grow on trees to take advantage of the sunlight in the canopy.

Epiphytes: This tree has Bromeliads and mosses living on the surface of its bark.

The leaves of Bromeliads form a vase to hold water. The pineapple is an example of a bromeliad.

Another bromeliad.

Rhizophora: In deltas and along ocean edges and river estuaries, trees have adapted to living in wet, marshy conditions. These trees, called mangroves, have wide-spreading stilt roots that support the trees in the tidal mud and trap nutritious organic matter.

Desert plants have adapted to the extremes of heat and aridity by using both physical and behavioral mechanisms, much like desert animals.

Xerophytes, such as cacti, usually have special means of storing and conserving water. They often have few or no leaves, which reduces transpiration.

Xerophytes adaptations:1. Thick cuticle.2. Stomata hidden in crypts or depressions in leaf surface (less exposure to wind and sun).3. Reduction in size of transpiration surface (lower leaf only).4. Increased water storage.5. Thicker leaves and stems, or leaves reduced in #, or leaves drop off during dry season.6. Leaves covered with silvery hairs (creates wind break & light reflective surface). 7. Deep taproots or wide spreading fibrous roots near the soil surface.

Phreatophytes are another group of plants that have adapted to arid environments. Phreatophytes, like the mesquite tree, have adapted to desert conditions by developing extremely long root systems to draw water from deep underground near the water table.

The Creosote Bush is one of the most successful of all desert species because it utilizes a combination of many adaptations. Instead of thorns, it relies for protection on a smell and taste wildlife find unpleasant. It has tiny leaves that close their stomata (pores) during the day to avoid water loss and open them at night to absorb moisture. Creosote has an extensive double root system -- both radial and deep -- to accumulate water from both surface and ground water.

Some plants, such as the Ocotillo, survive by becoming dormant during dry periods, then springing to life when water becomes available.

The Ocotillo also has a waxy coating on stems which serves to seal in moisture during periods of dormancy.

Another example of plants that utilize dormancy as a means of evading drought are bulbs, members of the lily family. The tops of bulbs dry out completely and leave no trace of their existence above ground during dormant periods.

The Desert Lily is found at a depth of 18 inches or more. Adequate winter rains can rouse it to life after years of dormancy.

Desert plants must act quickly when heat, moisture and light inform them it's time to bloom. Ephemerals send out flower stalks in a few days.

Ephemerals such as the Desert Sand Verbena usually germinate in the spring following winter rains. They grow quickly, flower and produce seeds before dying and scattering their seeds to the desert floor.

The Desert Paintbrush is another ephemeral that quickly blooms and scatters its seeds when it is active.

Supportive adaptations: many plants have developed adaptations that help them be more supported in order to grow taller and stronger. Some tropical trees have buttress roots, which are roots that come out from the lower part of the trunk and grow into the ground.

Prop roots: Some trees grow in very unstable soil, and the complex prop root system helps keep the tree stable in an unstable environment.  You can find an example of prop roots when looking at red mangroves. 

Prop roots on corn.

Epiphytes and vines also have special roots that help them grab onto a tree’s bark and stay put.

Defensive adaptations:

Plants as we know have evolved ways to defend themselves by using sharp spines, thorns or hairs; cellulose that makes them hard to digest, or creating toxic chemicals.  Another unusual way some plants have evolved to defend themselves is through mimicry - that is they evolve to look like another plant that is poisonous and animals are fooled into believing that they are poisonous.

Because weather conditions in the arctic and alpine tundra are unpredictable, plants need to adapt to all sorts of weather. Being close to the dark, warmth-absorbing soil helps to keep plants from freezing.

Instead perennials are more hardy of a plant for the tundra. They are plants which do not die in the winter because they keep their leaves, shoots and sometimes just roots in the ground. They quickly grow when the short growing season starts.

Another way plants have adapted is by how their seeds are dispersed. Some seeds hitch a ride on passersby using tiny hooks that snag on fur or clothing, only to be brushed off later far from the parent plant.

Other plants, like the dandelion have seeds better adapted to be caught by the wind and transported to another location.

The seeds of maple trees are also very aerodynamic. They mimic wings.

Aquatic plants like this fringed water lily have not needed adaptations for strengthening themselves. They are supported by the water they live in. They also do not need as many roots since they live in the water.

Many aquatic plants have very specialized leaf shapes. The submerged leaves are often very divided. This has the advantage of creating a very large surface area for absorbing water and for photosynthesis.

Pitcher plants (nepenthes) are named after an unusual adaptation. They have a structure shaped like a pitcher or vase that acts as a trap. The trap contains a fluid that the plant produces. This fluid is used to drown the prey. The lower part of the trap contains glands which absorb nutrients from captured prey.

That’s right! Pitcher plants are carnivorous.

“There is no doubt that tropical pitcher plants (Nepenthes) eat prey: they attract it, kill it and absorb the products of digestion.”

-June 2000, The Enduring Controversies Concerning the Process of Protein Digestion in Nepenthes (Nepenthaceae), International Carnivorous Plant Society Newsletter. http://www.carnivorousplants.org/cpn/samples/Science292Digest.htm