Introduction

Growth

Growth is one of the characteristics of living things. It is an increase in plant's height, weight and cell size. Growth in living things occurs at different rates in their lifespan. Usually all living things grow rapidly during their early stages until they are about to mature. The growth rate after maturity starts to decrease and stop at a certain period. The organism will eventually die.

Plants grow well when all essential needs for growth are available. The following illustration shows all essential needs for plant growth.

Essential needs for plant growth

The Essential Needs for Plant Growth

• Sunlight
• Air
• Water
• Nutrients

Sunlight

1. Role in Plant Growth: Sunlight is crucial for plant growth as it provides the energy required for photosynthesis. Plants use sunlight to create their food through a process called photosynthesis.
2. Photosynthesis: Plants absorb sunlight through chlorophyll in their leaves. Chlorophyll captures sunlight energy, which enables the plant to produce food.
3. Effect of Sunlight Intensity:
   • As sunlight intensity increases, the rate of photosynthesis also increases.
   • However, if sunlight intensity becomes too high, it can destroy chlorophyll, leading to a decrease in the rate of photosynthesis.
   • If the intensity continues to increase, photosynthesis may stop altogether.

Air

1. Role in Plant Growth: Plants need air for photosynthesis. The carbon dioxide in the air is used by plants to produce food.
2. Process of Absorption:
   • Carbon dioxide enters the plant through stomata pores in the leaves.
   • The stomata open to absorb the gas, which is a key component in photosynthesis.
3. Maintaining Carbon Dioxide Levels:
   • The concentration of carbon dioxide in the atmosphere remains relatively constant due to respiration in living organisms and the decomposition of plant and animal matter.
   • Additional carbon dioxide is produced by human activities such as the combustion of fuels in vehicles and machines, as well as natural events like volcanic eruptions.

Water

1. Role in Plant Growth: Water is vital for plant growth and is a necessary raw material for photosynthesis.
2. Absorption of Water:
   • Plants absorb water from the soil through their roots, which contain tiny root hairs that absorb water by osmosis.
   • Water travels through the plant's root hairs, to the main root, stem, and finally to the leaves.
3. Importance of Water in Plant Growth:
   • Nutrient Transport: Water helps dissolve nutrients in the soil, making them easier for plants to absorb.
   • Transport of Carbohydrates: Water transports carbohydrates and other nutrients from the leaves to other parts of the plant.
   • Temperature Regulation: Water helps regulate the plant's temperature, mainly through transpiration.
   • Support for the Plant: When plant cells are filled with water, they become turgid, providing mechanical support to the plant.
   • Photosynthesis: Water is a raw material used in the process of photosynthesis.

Nutrients

1. Role in Plant Growth: Plants require various nutrients for their proper growth. These nutrients are essential for healthy development and metabolic processes.
2. Absorption of Nutrients:
   • Plants absorb nutrients from the soil or other media where they grow. Some plants can even grow in water, without soil.
   • Nutrient absorption occurs through osmosis via the root hairs near the root tip.
3. Transportation of Nutrients:
   • After absorption, nutrients are transported through the xylem tissue to the main root and stem.
   • The nutrients are eventually carried to the leaves, where they are used in growth processes.