How Plants Adapt to their Environment

Adaptation is the process of change by which an organism becomes better suited to its environment. Either the organism is facing a new environment, or is dealing with changes in its old environment (as in climate change). The organism then needs to adapt in a way that offers it the best chance to survive. Biological adaptations can be passed on to off-spring, so that the future generations have a greater chance of reproduction and hence survival of the entire species.

Adaptation in the Desert
Plants adapt to their environment from necessity. For example, plants may adapt by growing lower and closer to the ground to shield themselves from wind and cold. The following adaptation of desert plants help them to conserve food, energy and water and still be able to reproduce effectively.

Many desert plants may have a thick waxy cuticle (a protective layer on the surface of stem and leaves) to prevent dehydration. For example, both agave and cacti show such adaptation. A succulent must be able to absorb large quantities of water in short periods because desert rains are often light and brief, and the soil dries rapidly under an intense sun. These succulent plants store water in fleshy leaves, stems or roots. Apart from cacti, non-cactus plants such as agave, aloe, elephant trees, and many euphorbias are succulents.

Most desert plants have thick, fleshy leaves to store water. Succulent plants like Agave victoriae-reginae store water in their leaf blades.

Desert plants usually have a shallow root system to collect small amounts of moisture. Or else they may have extremely deep root systems to tap into underground water.

They have light coloured leaves or small reflective hairs to reflect excessive light, normally grey or silver, to help keep them cool. Such plants show reduced leaf size since transpiration (loss of water through the plant, mainly the stomata, the pores on the leaves) takes place through leaves. The tiny leaves on this pink fairy duster plant are examples of a reduced leaf surface area, making the plant more water efficient.

Sometimes, there is a complete transformation of the leaves e.g. they are reduced to thorns or spines. These also offer protection against predators. This prickly pear cactus not only stores water in its succulent pads (stems), it also protects itself from hungry predators with its spines. Spines also help shade the plant and to capture moisture.

Plants like euphorbia have toxic sap to deter insects.

Desert plants flower infrequently and produce large amounts of seed e.g. cacti. Flowers are often light coloured and have no pigment.

Adaptation in the Rainforest
A rainforest is a rich and dense forest found in areas with high rainfall, in contrast to a desert climate. The canopy, where more species live than anyplace else in the rainforest, is the denser layer of greenery about 6 meters thick formed by the next tallest trees. It acts like a roof over the rest of the rainforest. Plants in rainforests have an extra struggle to survive as they seek the sun through layers of vegetation, with extreme heat and humidity.

In drier, temperate deciduous forests a thick bark helps to limit moisture evaporation from the tree's trunk. Since this is not a concern in the high humidity of tropical rainforests, most trees have a thin, smooth bark. 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. That is, their leaves and flowers grow in the canopy where they are exposed to sunlight that enables photosynthesis.

The leaves of forest trees have adapted to cope with exceptionally high rainfall by having "drip tips". It is thought that these drip tips enable rain drops to run off quickly. Plants need to shed water to avoid growth of fungus and bacteria in the warm, wet tropical rainforest.

Many large trees have buttresses. A buttress means a support or reinforcement that strengthens a structure. Many large trees have massive ridges near the base that can rise 30 feet high before blending into the trunk. Buttress roots provide extra stability. Trees like fig, silk-cotton (kapok) and jackfruit tree, all have buttress roots -- these are large, wide roots on all sides of a shallowly rooted tree. Typically, they are found in nutrient-poor tropical forest soils that may not be very deep, and prevent the tree from falling over.

Prop and stilt roots help give support and are characteristic of tropical palms growing in shallow, wet soils. See the stilt roots of the maize plant in the picture.

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. Most are orchids, bromeliads, ferns, and Philodendron relatives.

Bromeliads are found mostly in the Americas. Some grow in the ground, like pineapple, but most species grow on the branches of trees. Their leaves form a vase or tank that holds water. The tanks support a thriving eco-system of bacteria, mosquito and dragonfly larvae, tadpoles, birds, salamanders and frogs.

Most famous of rainforests are Mangroves which are found in many parts of India along both the east and west coasts. Mangroves an be found on tropical deltas and along ocean edges and even river estuaries. These 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.

A very curious type of plants are the Nepenthes. A common example is the Pitcher plant. Here the vines have leaves that form a pitcher (jug), complete with a lid. Sweet or foul-smelling nectar in the pitcher attracts insects, especially ants and flies, that lose their grip on the slick sides and fall into the liquid. Downward-pointing hairs inside the pitcher prevent the insects' escape. The insects are digested by the plants and provide nutrients. Pitcher plants are not epiphytes but climbers rooted in the soil.

Every plant has adapted in various ways to survive best in the environment it has found itself in. Animals also adapt to their environment, but that is another story!

Sources:
https://www.botanic.co.uk/wp-content/uploads/2017/05/8_1__tttTeachers_Notes_Awesome_Adaptations.pdf;
https://wateruseitwisely.com/blog/how-do-those-desert-plants-survive/;
https://www.bbc.co.uk/bitesize/guides/zx8n39q/revision/2;
Images from Wikipedia