Life Processes in Plants
Plants make their own food and quietly carry out the same life processes as animals in their own way. This Class 7 Curiosity chapter covers photosynthesis, how water and food are transported through the plant, transpiration, and respiration in plants.
Learning objectives
- Explain photosynthesis and its requirements.
- Describe transport of water and food in plants.
- Explain transpiration.
- Describe respiration in plants.
Key concepts
Photosynthesis
Plants make their own food by photosynthesis, in which green leaves use sunlight, carbon dioxide from the air and water from the soil to make food (a sugar) and release oxygen. The green pigment chlorophyll captures sunlight, which is why leaves are the main food factories of the plant.
Transport in plants
Plants have two transport tissues. Xylem carries water and dissolved minerals upward from the roots to the leaves, while phloem carries the food made in the leaves to all other parts of the plant. This two-way transport keeps every part of the plant supplied.
Transpiration
Transpiration is the loss of water as vapour from the leaves, mainly through tiny pores called stomata. It helps pull water up from the roots and cools the plant. On a hot day a plant loses a lot of water this way, which is why plants need a steady water supply.
Respiration in plants
Like animals, plants respire all the time, using oxygen to release energy from food and giving out carbon dioxide. Respiration happens day and night in every living cell. During the day, photosynthesis also occurs, and plants take in carbon dioxide and release oxygen overall when light is bright.
Important formulas
Photosynthesis
carbon dioxide + water → food + oxygen (in sunlight, using chlorophyll)
Key definitions
- Photosynthesis
- The making of food by green plants using sunlight, carbon dioxide and water.
- Chlorophyll
- The green pigment in leaves that captures sunlight.
- Xylem
- The tissue that carries water and minerals up from the roots.
- Stomata
- Tiny pores on leaves through which gases and water vapour pass.
Solved examples
Q1. Which gas do plants take in for photosynthesis?
Solution: Carbon dioxide.
Q2. Which tissue carries water up the plant?
Solution: Xylem.
Q3. Through which pores does transpiration mainly occur?
Solution: The stomata.
Common mistakes to avoid
- Thinking plants do not respire (they respire day and night).
- Confusing xylem (water) with phloem (food).
- Believing photosynthesis releases carbon dioxide (it releases oxygen).
- Forgetting that chlorophyll is needed to capture sunlight.
Life Processes in Plants — MCQ Quiz
10 questions with instant feedback. Use number keys 1–4 to answer.
Plants make their food by:
Practice questions
Short answer
What is photosynthesis?
The process by which green plants make food using sunlight, carbon dioxide and water.
What does xylem carry?
Water and dissolved minerals, upward from the roots.
What is transpiration?
The loss of water as vapour from leaves through stomata.
Long answer
Explain photosynthesis, including its raw materials and products.
Photosynthesis is the process by which green plants make their own food. It takes place mainly in the leaves, where the green pigment chlorophyll captures energy from sunlight. Using this energy, the plant combines carbon dioxide taken from the air through the stomata with water absorbed from the soil by the roots, producing food in the form of a sugar and releasing oxygen as a by-product. The raw materials are therefore sunlight, carbon dioxide and water, and the products are food and oxygen. Because of this, green plants are the original source of food and oxygen for almost all living things.
Describe how materials are transported in a plant and the role of transpiration.
A plant moves materials using two transport tissues. Xylem carries water and dissolved minerals upward from the roots to the leaves, while phloem carries the food made in the leaves to all other parts of the plant, including the roots. Transpiration, the loss of water as vapour from the leaves through tiny pores called stomata, plays an important role in this transport: as water evaporates from the leaves, it helps pull more water up through the xylem from the roots, rather like sucking through a straw. Transpiration also cools the plant. Because a plant can lose a lot of water this way, especially on hot days, it needs a steady supply of water from the soil.
HOTS (Higher Order Thinking)
Why is the leaf called the food factory of the plant?
Because leaves contain chlorophyll and carry out photosynthesis, making the plant's food using sunlight, carbon dioxide and water.
Why might a plant wilt on a very hot day even with some water in the soil?
Because transpiration removes water faster than the roots can replace it, so the plant loses water and wilts.
Quick revision
Revision notes
- Photosynthesis: sunlight + CO₂ + water → food + oxygen (needs chlorophyll).
- Xylem carries water up; phloem carries food.
- Transpiration: water vapour lost via stomata; pulls water up and cools.
- Plants respire day and night (use O₂, give out CO₂).
Key takeaways
- Plants make food by photosynthesis and release oxygen.
- Xylem moves water up; phloem moves food.
- Plants respire continuously, not only at night.
Frequently asked questions
What does a plant need for photosynthesis?
Sunlight, carbon dioxide, water and chlorophyll.
What is the difference between xylem and phloem?
Xylem carries water and minerals up; phloem carries food to all parts.
Do plants respire?
Yes, all the time — using oxygen and giving out carbon dioxide.