# Life Processes in Plants

## Overview
This chapter explores how plants grow, prepare their own food through photosynthesis, transport substances, and respire. Through various experiments and observations, students understand the key roles of water, sunlight, carbon dioxide, and chlorophyll in plant life processes. The chapter highlights the structure and function of leaves, transport systems like xylem and phloem, and the importance of stomata.

## Key Topics Covered

### 1. How Do Plants Grow?
- Plants grow by developing new leaves, branches, increasing height, and thickening stems.
- Growth is influenced by sunlight and water.
- **Activity 10.1** demonstrated plant growth under three conditions:
- Sunlight + Water → Maximum growth
- Sunlight + No Water → Minimal growth or plant dies
- Water + No Sunlight → Poor growth, yellow leaves
- Conclusion: Both sunlight and water are essential for plant growth.

### 2. How Do Plants Get Food for Their Growth?

#### 2.1 Leaves: The ‘Food Factories’ of Plants
- Leaves store food as starch, a carbohydrate.
- They are mostly green due to **chlorophyll**, which helps capture sunlight.
- **Activity 10.2**: An iodine test on a decolourised leaf shows blue-black colour where starch is present.
- **Activity 10.3**: Leaves from plants exposed to sunlight (with green patches) show starch presence; non-green parts or leaves kept in the dark do not.

#### 2.2 Role of Air in the Preparation of Food
- Plants need **carbon dioxide** from the air to prepare food.
- **Activity 10.4**: A destarched plant leaf placed partly in a CO₂-free bottle did not form starch in that part.
- Conclusion: CO₂ is essential for photosynthesis.

#### 2.3 Photosynthesis in a Nutshell
- Photosynthesis occurs in the presence of sunlight, water, carbon dioxide, and chlorophyll.
- It produces glucose (used for energy or stored as starch) and releases oxygen.
- **Word Equation**:


Carbon dioxide + Water --(Sunlight, Chlorophyll)--> Glucose + Oxygen


#### 2.4 Exchange of Gases: Role of Stomata
- Stomata are tiny pores on the leaf surface that help exchange oxygen and carbon dioxide.
- **Activity 10.6**: Peeling a leaf and viewing under a microscope reveals stomata.

### 3. Transport in Plants

#### 3.1 Transport of Water and Minerals
- Water and minerals are absorbed by roots from the soil.
- **Xylem**, a tube-like structure, transports these nutrients upward to stems, leaves, and flowers.
- **Activity 10.7**: A plant placed in red ink water showed red streaks through stem and leaves, proving water transport through xylem.

#### 3.2 Transport of Food
- Food prepared in leaves is transported to all parts of the plant through **phloem**.
- It may be stored in seeds, roots, or other plant parts.
- Diagrammatic representation explains transport through xylem (water and minerals) and phloem (food).

### 4. Do Plants Respire?
- Plants also respire like animals.
- During respiration, **glucose** is broken down with oxygen to produce **carbon dioxide**, **water**, and **energy**.
- **Word Equation**:

Glucose + Oxygen → Carbon dioxide + Water + Energy

- **Activity 10.8**: Germinating seeds produce carbon dioxide, turning lime water milky, proving respiration in plants.
- All parts of plants, including green and non-green, carry out respiration.

## New Terms and Simple Definitions

| Term | Simple Definition |
|-----------------|------------------|
| Chlorophyll | Green pigment in leaves that helps absorb sunlight for food preparation |
| Photosynthesis | Process by which plants make food using sunlight, water, and carbon dioxide |
| Starch | A type of carbohydrate stored in plants |
| Xylem | Tubes that carry water and minerals from roots to other parts of the plant |
| Phloem | Tubes that carry food from the leaves to other parts of the plant |
| Stomata | Tiny openings on the leaf surface that allow gas exchange |
| Respiration | Process of breaking down food to release energy |
| Glucose | A simple sugar made during photosynthesis |
| Carbon dioxide | A gas taken in by plants for making food |
| Oxygen | A gas released by plants during photosynthesis |

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## Practice Questions

### Easy (3)

1. **What is the role of chlorophyll in plants?**
*Answer*: It helps in absorbing sunlight for photosynthesis.

2. **Name the two main transport tissues in plants.**
*Answer*: Xylem and Phloem.

3. **What gas is released during photosynthesis?**
*Answer*: Oxygen.

### Medium (2)

4. **Why do leaves turn blue-black in the iodine test?**
*Answer*: Because of the presence of starch, which reacts with iodine.

5. **What will happen to a plant if it doesn’t get sunlight?**
*Answer*: It cannot perform photosynthesis and will have poor growth.

### Difficult (3)

6. **How does carbon dioxide enter the plant for photosynthesis?**
*Answer*: Through tiny pores in leaves called stomata.

7. **Differentiate between xylem and phloem.**
*Answer*: Xylem transports water and minerals from roots; phloem transports food from leaves.

8. **What does the experiment using caustic soda demonstrate?**
*Answer*: It shows carbon dioxide is essential for photosynthesis.

### Very Difficult (2)

9. **Describe an experiment that proves plants respire. What does the result indicate?**
*Answer*: Soaked moong seeds in a flask release carbon dioxide which turns lime water milky, indicating respiration.

10. **Explain the significance of photosynthesis and respiration in maintaining balance in nature.**
*Answer*: Photosynthesis produces oxygen and food; respiration uses oxygen to release energy and produces carbon dioxide—both keep atmospheric gases balanced and support life.

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