ADAPTATIONS IN PLANTS
Natural home of a plant is called its habitat. Each habitat has its own characteristic, i.e., some places are warm, some are hot, some are cold and some are very cold. Some places get a lot of rainfall while others are dry.
Plants have special features to live successfully in their respective surroundings and have adjusted themselves to the different habitats on Earth e.g., desert plants try to save whatever water is available and hence have adjusted well with low water conditions. This process of adjusting or changing to suit the environment is called adaptation.
Adaptations in Terrestrial Plants:
Plants that grow on land are called terrestrial plants. As there are different land forms like plains, hills, deserts, swamps, etc., there are different types of plants growing in each of these habitats.
Plants growing in the plains:
Plains have a moderate climate. It is neither too hot nor too cold. The climate is warm to hot in summer and cold in winter. The rainfall is just sufficient for plant growth. As the climate is well suited for plant growth, many kinds of plants grow here. Trees growing in the plains have lots of h e branches e.g., neem, peepal, mango, banyan, etc.
- Most trees growing in plains usually shed their leaves in winter to protect themselves from the cold weather and get new leaves again in spring. Such trees are called deciduous trees, e.g., oak, maple, elm, etc.
- Certain trees do not shed their leaves and remain green throughout the year. Such trees are called evergreen trees, e.g., some varieties of neem plant.
- In plains, where it rains heavily, tall and thick trees (e.g., teak, rubber, etc.) and some short trees and climbers grow. Such areas are called rainforests which are home to many animals. Most rainforests are found in South America, Asia, Africa and Australia.
Plants growing on hills:
The climate on hills and mountains is cold to very cold. During winter, there is snowfall in some areas therefore, the plants growing on hills are well adapted to such weather conditions.
|Pine tree (evergreen)||Needle – like leaves and Woody cone of a pine tree|
- Sloping shape of trees helps to slide off the snow easily. This helps to prevent damage to the plant and its parts due to extreme cold.
- Leaves are needle shaped with waxy coating. This helps to prevent any damage from the snow.
- These trees have woody cones instead of flowers. That is why they are called coniferous trees. The cones are very hard and bear seeds inside them e.g., pine, spruce, cedar, fir etc.
- Most of the conifers are evergreen trees e.g., pine, spruce, cedar and some conifers are deciduous trees e.g., larch.
Plants growing in deserts:
Climate in deserts is hot, dry and dusty. There is shortage of water. Inspite of all these disadvantages, plants grow in deserts with certain special features.
|Desert Oak, found in Australia has roots that are 30 times longer than its trunk. The roots go very deep into the ground to reach water. This water is then stored in the trunk. When there is no water in the desert, local people put thin pipes into the trunk of this tree, to drink water.|
- Certain plants, like Acacia or babool have small leaves to prevent water loss through transpiration. Transpiration is the process of losing water in the form of vapour through the stomata of leaves.
- Some plants, such as date palms, have strong and hard leaves which help them to survive in hot and dry deserts.
- Certain plants, like mesquite tree, have roots that go down up to 20 metres under the ground in search of water.
- In some desert plants, the stomata are found deep into the leaves rather than on the surface of the leaves. Hence, they are called sunken stomata. This reduces water loss through stomata.
- Certain plants, like cactus, have leaves modified into spines that help in preventing water loss through stomata. These spines discourage animals from eating them. The green stem stores water and carries out photosynthesis
|Acacia tree||Date palm||Cactus|
Plants growing in swamps or marshes:
Marshes have clayey soil with plenty of water. The soil is sticky and does not have enough air for the roots of the plants to breathe.
To withstand these problems, the trees growing in marshy areas have roots growing out of the water-logged soil to breathe air. Such roots are called breathing roots. Mangrove trees grow in marshes e.g., sundari tree (a mangrove tree) found in Sundarbans.
Plants growing in sea coasts:
The coastal areas have hot and wet climate. Trees growing in coastal areas should be able to withstand salty water, strong winds and heavy rainfall.
|Coconut tree||Pepper plant|
The trees growing here are usually tall and straight. They have a crown of giant, feather-like leaves which allow the wind to pass through. They are adapted to grow well in salty water. Their fruits and seeds are scattered by water. Some examples are trees of coconut, pepper.
Adaptations in Aquatic Plants:
Plants growing in water (ponds, lakes, seas, oceans) are called aquatic plants. Aquatic plants are of three types- fixed, floating and underwater plants.
- The roots of such plants are much reduced and are fixed to the mud at the bottom of the pond.
- The stems are long, hollow, light and flexible so that they stay afloat and can bend easily with the waves of water and do not get broken or uprooted.
- Their leaves are broad and flat which help in staying afloat and to get enough air and sunlight for photosynthesis.
- Stomata are on the upper side of the leaves so that they can breathe easily.
- The leaves of fixed plants have a waxy coating on their surface so that water cannot stay on them. This prevents them from rotting or shrivelling up. Some examples are water lily, lotus, etc.
- These plants float freely in water as they have spongy bodies filled with air.
- They are not fixed at the bottom of the water body. Their roots just float below the water surface.
- They are small and light in weight. Some examples are duckweed, water lettuce and water hyacinth.
|Duckweed||Water hyacinth||Water lettuce|
Some plants like Hydrilla and tape grass remain completely submerged in water. So, they are called underwater or submerged plants.
- These plants have thin and narrow leaves with flexible stems to withstand water currents. Hydrilla has tiny leaves and the leaves of tape grass are ribbon-like.
- Their roots are fixed to the bottom of the pond.
- The leaves of underwater plants have no stomata at all. They breathe the dissolved oxygen through their body surface.
Plants are primarily known for their green colour due to chlorophyll and their self-dependence for food. However, there are certain plants which show different types of nutrition.
Some plants like dodder do not make their own food, but absorb food from other plants. Such plants are called parasites. Some examples are Dodder, Corpse flower and Australian Christmas tree.
There are some plants which eat insects. Such plants are known as insectivorous plants. These plants are green in colour and make their own food but they grow in soil which is poor in minerals. So, they trap and eat insects to fulfil their nutrient requirement. Some examples are Venus fly trap and pitcher plant.
- In pitcher plant, the leaf is modified into a pitcher with a lid which can open and close. The pitcher is filled with a special nectar (digestive liquid). Whenever an insect comes to feed on this nectar and sits on the edge of the pitcher, the lid closes and the insect is trapped inside. The insect gets digested from which the plant can obtain its mineral nutrition.
- The leaves of Venus fly trap are like boxes with hinges. They have long hair along the edges. When an insect touches the hair, the leaf closes rapidly, trapping the insect inside. The insect gets gradually digested.
|Venus flytrap||Pitcher plant|
|Venus Flytraps: Venus Fly Traps. Attracts small insects with sweet smelling nectar, then snaps shut and digests the meal.|
Pitcher plants: Pitcher plants are shaped like vases, or pitchers, and resemble flowers in look and smell. Pitcher plants color, nectar and scent lure in and trap insects. Hairs and digestive acids inside the plant ensure insects cannot escape, becoming a meal for the pitcher plant. Pitcher plants slowly break down the insect and absorb essential nutrients for survival.
Bladderwort: Bladderwort is unique in that the underwater leaves bear small oval “bladders” that trap and digest small aquatic creatures. Bladderwort is usually found in quiet shallow, acidic waters and can form dense mats.
Sundews(Drosera): Sundews are “flypaper” plants that trap prey in sticky hairs on their leaves. They make up one of the largest groups of carnivorous plants. Long tentacles protrude from their leaves, each with a sticky gland at the tip. These droplets look like dew glistening in the sun, thus their name.
Fungi are organisms that cannot make their own food by photosynthesis as they do not have chlorophyll. They absorb nutrients from dead and decaying plants, animals or stale food. They are also called saprophytes. Moulds and mushrooms are some examples of fungi.
Sometimes, bread slices change colour when you keep them for longer time at room temperature. This is because of the growth of moulds on them.
PLANTS OF GRASS FAMILY
Plants of grass family are useful to us in many ways:
- They provide food, e.g., wheat, rice, bajra, jowar, sugarcane, etc.
- Bamboo plants are tall plants. They are used for making furniture, mats, baskets, etc. Young bamboo shoots are used to prepare food items, like curry, pickles, etc. It has high nutritive value.
- Some grasses are used to make paper. Paper was first made in Egypt from a grass called papyrus.
- The grass family has fibrous roots which hold the soil tightly and protect it against erosion.
- Dried grass is used as packing materials and for side cover of air coolers.
- Some grass family plants are used in preparing medicines e.g., lemon grass.
USES OF PLANTS
- Plants are producers. They produce food in the form of fruits, vegetables, pulses, grains, spices, nuts, etc., that are required by animals to survive.
- Plants produce oxygen during the day by the process of photosynthesis which is used by animals for breathing.
- Plants provide us with medicines, oil, rubber, wood, paper, etc.
- Plants such as cotton, jute and flax provide us with fibres used to makes clothes, bags, etc.
- Plants maintain the balance of oxygen and carbon dioxide gases in atmosphere.
- Plants help to beautify our surroundings.