Leaves are green colored organs present on all the living plants.
They are greenish due to the presence of a pigment named chlorophyll.
Unlike other parts of the plant, they are highly active. Many leaves are formed over the plant and shed off every year.
This shows their active role in the plant physiology. Both the formation of leaves and their shedding is also essential for the plant.
Leaves are tender, flat and flexible in structure. They tend to get erect in the day and lie down drooped in the night.
Uses of leaves / Importance of leaves
1. Oxygen production: Oxygen is vital for life. When we breathe oxygen, it enters our body cells and tissues and generates energy from glucose. This energy helps us perform all our daily work.
Air has 21% of oxygen. And when all the animals breath daily and release out carbon dioxide, this oxygen ratio can go down and we might suffocate.But green leaves release oxygen during the process of photosynthesis. Thus they help to maintain the proper oxygen ratio in the air.
2. Removes excess carbon dioxide: Besides consumption of oxygen, we also leave out carbon dioxide during expiration. This release of carbon dioxide is also further added up when we burn some wood or fossil fuels. So this can drastically enhance the carbon-dioxide levels in the air which could be harmful to all the animals on the earth.
Interestingly, plant leaves take in carbon-dioxide as a part of photosynthesis.
During the process, they take up carbon-dioxide and along with water help in the formation of sugars like glucose in the presence of sunlight. Thus they take up large volumes of CO2 from the air and help in bringing down its levels. Since carbon dioxide is one of the greenhouse gases, its increase can enhance global warming. So plant through leaves can keep a check on carbon-dioxide.
3. Decrease the temperature: In general, the presence of green trees is considered necessary for low temperatures during summers. This is true as plants minimize greenhouse gas effects. But the other mechanisms involved are through leaves of the plants.
Leaf pigments absorb light from the sun and store it in the form of chemical energy. Thus the light reflected back into space from plants is low. Also, leaves have large amounts of stomata which expel the water by the process called as transpiration. This sending of water into the air also reduces the temperature.
Thus leaves help to lower the atmospheric temperature around us.
3. Food production: Plants are involved in food production. They prepare sugar which is stored in fruits, seeds and tuber (potatoes) of plants. Also, some leaves become succulent and eatable. There are also many green leafy vegetables which are rich in iron and can be used as part of our food. There are some thousands of edible leaves which can be taken as a part of our diet.
Hence we can see leaves in all the ecosystems. Many insects, cattle depend on leaves for food, Similarly, in the marine ecosystem, small fishes and big mammals like sea buffalo, whales depend on leaves for food.
4. Medicine: Leaves are the biggest source of medicine from natural resources. Many leaves like that of digitalis, vinca, alove are excellent sources of medicine. Digitoxin from the leaves of digitalis plant is used in case of heart failure, vincristine from vinca plants is a drug for treatment of cancer, aloe leaves have moisturizing properties which help to heal the dryness of skin.
5. Commercial tobacco: Tobacco which is widely used in cigars and other smoking and chewing products is obtained from the leaves of tobacco.
6. Fiber: Few leaves are the source for good quality fiber for making ropes and threads. Examples of plant whose leaves are used for the purpose include hemp, Henequen, sisal, abaca, etc. These fibers are hard and coarse.
7. Dyes: Leaves are also sources of colors and dyes. Unlike synthetic ones, these are obtained from nature so the process is called as eco dyeing or eco printing. Many leaves like
Eucalyptus: Dark Tan
Coneflower: Brownish green
Fennel leaves: golden brown etc. are the plants whose leaves can be used for extraction of dyes.
8. Home construction: Leaves especially the large ones are used for house construction. These are specifically used for rooftop for small huts or even houses made of mud. They keep the house cool as they are bad conductors of heat, unlike reinforced cement concrete buildings.
9. Small Utensils: Though not large ones, leaves are traditionally used in making small utensils like cups and also used as plates. They are nature-friendly, disposable and also have no untoward effects on humans. Leaves are knitted into cups or plates and dried latter in the sun, to make them slightly harder. Then they are used for serving dishes, eating, drinking etc.
Leaves used for the purpose are
- Banana plan leaves,
- Palm leaves
- Areca etc.
10. Communication and records: Before books and paper were manufactured, palm leaves were used for writing scripts and other literature.
They were used for quite a long time in this manner in different parts of the world. They are said to be used since 5th century BC onward. These are called as palm leaf manuscripts.
Besides the above, leaves are also helpful to plants to expel the waste. Leaves shed at the regular time interval and new ones are formed in the plant. Plant during its course of living generates nitrogenous waste and is stored as alkaloids in the leaves. When leaves dry and shed off, this helps to remove the waste away from the plant.
For plants: As mentioned before, they contribute to food (photosynthesis), gaseous exchange and waste excretion.
For Ecosystem: They maintain oxygen levels, decrease temperatures and act as source of food for other animals.