Plant Adaptations: Desert, Tropical Rainforest, Tundra

Diverse marine, aquatic and terrestrial plants evolved long before dinosaurs roamed the Earth. From their humble beginnings as single-celled algae, plants have evolved clever adaptations to survive and reproduce even in the harshest environments.

Charles Darwin's theory of evolution helps explain how plant adaptions occur as the result of inherited physical and behavioral characteristics passed down from parent to offspring.

You can find fascinating examples of plant adaptions when comparing vegetation in desert, tropical rainforest and tundra biomes.

Biomes are areas of similar climate and temperature that have distinctive plants and animals that have adapted to the conditions of the region. Similar biomes can be found in discontinuous geographical areas.

Biomes around the world are divided into broad categories such as the desert, tundra and rainforest biome. Adaptations are nature's way of helping animal and plant populations survive in a particular biome.

Examples of biomes:

• Desert: succulents that store water, spiny leaves, low precipitation, high evaporation, extreme temperatures 
• Tundra: low trees and shrubs, small woody plants, cold, dry, windy conditions most of the year
• Rainforest: dense jungle, lush vegetation, heavy rain, high humidity, tropical, nutrient deficient soil
• Taiga: evergreen forests, snowy, cold winters, warmer and longer growing season than tundra
• Deciduous forest: broad-leaf trees that seasonally drop leaves, cold winters and hot summers
• Grasslands: treeless plain with grasses and woody plants, parched, natural fires common
• Chaparral: dense woodland, trees have thick, evergreen leaves, little rain in the summer
• Savannah: woodlands and grasslands, scarce trees, summers are hot and wet, fire and drought cycles

Plants contain genetic material in the nucleus of their cells that is passed down through generations. In any plant population, there will be **random mutations** during gamete cell division, as well as variations in behavior, physiology and other special features that give certain organisms an evolutionary edge.

Charles Darwin posited that this process leads to the evolution of structural adaptations in a population that improve fitness and viability.

Species wage a contest of "survival of the fittest," as described by early evolutionists. For example, behavioral adaptations include going dormant during unbearable heat or equally difficult conditions and returning later.

Similarly, desert plants with narrow leaves are more fit for retaining water in the desert than plants with broad leaves that have a wide surface area. Over time, plants that survive and reproduce become the dominant species via natural selection.

Nonvascular plants with simple structures such as mosses and liverworts were the first plants to adapt to a terrestrial environment. Ferns evolved next, followed by seed-bearing gymnosperms such as conifers and ginkgoes.

Flowering angiosperms including hardwood trees, grasses and shrubs evolved the ability to make seeds enclosed in protective ovules. Plant life proliferated after plants developed the ability to produce seeds that traveled long distances in the wind.

Gymnosperms were soon outnumbered by angiosperms that gained the evolutionary upper hand. Gymnosperms depend on the wind and water for seed dispersal; whereas, angiosperms rely on wind and water plus pollinators that are attracted to that plants' flowers and nectar. The fruit of angiosperms provides extra nutrition and protection for the seeds.

Today, flowering plants are ubiquitous around the world. Angiosperm pollen is smaller than male gymnosperm pollen, so it can reach eggs faster. Some types of seeds survive digestion when animals eat and excrete the seeds, which further aids their wide distribution and proliferation.

Deserts are arid lands that stay parched for long stretches of time. Without adaptations, plants would wither and die. Temperatures rise and fall to extremes, and some regions receive as little as 10 inches of annual rainfall. Seeds may be dormant for years before there is enough moisture to sprout.

Desert plants look very different from plants found in other biomes due to the methods that they have adapted to obtain water, store water and prevent water loss. Such specific adaptive strategies have evolved to help desert plants cope with conditions inhospitable to most living organisms.

Examples of plant adaptations:

Evening Primrose has a long, thick taproot that helps this plant reach and store water and nutrients. Like some cacti, the primrose plant becomes active at night, and flowers bloom when temperatures are cooler.

Pinyon pines have vertical and horizontal root systems that reach out 40 feet in both directions to provide water. Extensive root systems help the tree grow and produce edible pine nuts in resin coated cones that prevent water loss.

Juniper are gymnosperms with sharp, pointed needles or waxy scales adapted for less water loss. Long tap roots help these trees and shrubs reach deep into the bedrock for water. A slow growth rate expends less energy and helps preserve water. Junipers can even self-prune by cutting off water to a branch in times of drought to save the tree itself from dying.

Yucca have a long tap root for accessing sources of water that competing species cannot reach. Yucca also have an adaptive reproductive process with the yucca moth that mutually benefits the life cycle of both species. Yucca provide food for caterpillars that hatch into moths. The moths flit between yucca flowers laying eggs in the yucca plant's ovaries while pollinating the host plant in the process.

Cacti are succulents with a waxy coating that helps the plant retain water. Cacti open their stomata at night to reduce water loss through transpiration. Shallow roots are capable of multiplying quickly in the presence of moisture. Cacti have prickly spines instead of leaves to keep animals from eating the plant to obtain the water that is stored in parts of the cactus.

**Sagebrush** have "hairy" looking leaves that provide insulation from extreme temperatures and desert winds. Leaves are retained year-around, which enables the plant to photosynthesize even when the temperature drops sharply.

Tropical rainforests are warm and humid year-around. Tropical rainforests receive 80 to 400 inches of rain a year, which can lead to bacteria and fungi growth, soil erosion, nutrient leaching and poor soil quality.

Large canopy plants can block sunlight to the forest floor while those canopy plants must withstand almost constant daily sunlight in the tropics. Native plants in tropical rainforests have specific adaptations tailored to their unique ecosystem.

Tropical rainforests provide a habitat for more than two thirds of all plant species on Earth. The rainforest is also an important producer of oxygen and a sink for carbon dioxide pollutants.

Plants also provide food and habitat for unique birds, monkeys and jungle predators. Trees in the rainforest don't need insulating thick bark like deciduous trees to stay warm and hold on to water.

Examples of plant adaptations:

Carnivorous plants like the Venus fly trap have adapted the ability to catch and digest insects that are drawn to their colorful, scented flowers. The much larger pitcher plant can even eat small rodents or snakes that get too close. These plants also make food through photosynthesis but do not depend on soil for nutrients, relying instead on consumed animal proteins.

Buttress roots are huge woody ridges at the base of large trees that help keep these trees upright. Long prop or stilt roots on trees like mangroves or tropical palm trees provide added support when the soil is wet. The shallow root formation also helps with the absorption of nutrients.

**Epiphytic orchids** use other plants and trees as a growing surface without causing any harm. They are adapted to climbing up other plants to reach sunlight in the rainforest canopy.

Many trees in the rainforest have leaves, bark and flowers that are wax coated as an adaptation to handle excessive rainfall that can give rise to the growth of harmful bacteria and fungus. The leaf structure has a pointy end called a drip tip that speeds runoff when the plant receives too much water.

Amazon water lilies are giant aquatic plants native to South America. Adaptions include delicate free-floating leaves with sharp prickles on the underside for protection. Water lily flowers' blooms open at night and only last a couple days.

**Air plants** in the Bromeliad family do an excellent job removing atmospheric carbon dioxide. Aerial plants obtain moisture and nutrients from the air using an adapted root system called air roots. Such adaptations are only possible in warm, humid climates.

The Arctic and Alpine tundra biomes are the coldest places on Earth. The Arctic tundra stretches across Canada, Siberia and northern Alaska. Alpine tundras are found at elevations of 11,000 to 11,500 feet in places like the Rocky Mountains. Living organisms are sparse in Antarctica's extreme climate.

Most months in the tundra are extremely cold and windy. Winter is dry and the growing season of the cool summer months is short. Tundra biomes only receive 4-10 inches of rain annually.

Sources of soil nutrients are mainly nitrogen from decomposing matter along with phosphorus from precipitation. Nutrient-deficient soil further limits the type of plants that can establish there under such dry, windy conditions.

Examples of plant adaptations:

Arctic Flowers and dwarf shrubs have a shallow root system to absorb nutrients above the line of permafrost. Many species grow close together for warmth. Their leaves can photosynthesize at low temperatures. Examples of Arctic vegetation include willows, poppies and purple saxifrage. Not much grows in cold, icy Antarctica except for moss and lichens.

Cushion plants resemble clumps of moss clinging to the ground. Their long taproots penetrate rocky soil and provide an anchor during fierce winds.

Caribou mosses grow low to the ground to avoid the chilling winds. They are well adapted to nutrient poor substrates.

Grasses and sedges grow in spots where the tundra soil is well-drained and has adequate nutrients.

The Old-man-of-the mountain is a bright yellow wildflower that gets its name from its very hairy-looking appearance. Wooly leaves and stems provide insulation and buffer the wind.

Alpine sunflowers are bright yellow like the true sunflowers of the Helianthus family. Alpine flower heads face East throughout the day, instead of following the sun like Helianthus do, as an adaptation from strong afternoon thunderstorms rolling out of the west.

The **taiga biome** has some similarities to the tundra biome. The taiga, also called the boreal forest, is a once glaciated area within Eurasia and North America that has retained patches of **permafrost**. Like the Arctic tundra, plants in the taiga biome have adapted to difficult winters and few days without killing frost.

Needle-like leaves and waxy coats reduce water loss through transpiration. Dark colored foliage is an adaptation that helps with heat absorption and photosynthesis. Larch forests survive in places too cold and barren for conifers.

Examples of plant adaptations:

Spruce, pine, tamarack and fir thrive in cool temperatures and retain water.

Arctic cottongrass grows on mats of aquatic sphagnum moss.