INTERMEDIATE LEVEL: KEY PROCESSES AND FUNCTIONS IN PLANTS

Now that we know some basic plant structures, let’s dive into the processes that drive plant growth and health. Plants are complex organisms that carry out several vital processes to thrive in diverse environments.

Plants have two primary types of vascular tissue responsible for transporting materials throughout the plant:

Xylem – Transports water and minerals from the roots to the rest of the plant. Water is essential for photosynthesis, and minerals like nitrogen, phosphorus, and potassium are required for growth.
Phloem – Transports the products of photosynthesis (mainly sugars) from the leaves to other parts of the plant, such as the roots and flowers.

Meristems: Growth and Development

Plant growth occurs in specialised areas called meristems. There are two types of meristems:

Apical meristems – Found at the tips of roots and stems, responsible for primary growth, or lengthening.
Lateral meristems – Responsible for secondary growth, or thickening, found in woody plants.

Chloroplasts are the sites of photosynthesis, where light energy is converted into chemical energy. The process occurs in two stages:

Light-dependent reactions – These occur in the thylakoid membranes and require sunlight to generate ATP and NADPH, which are energy carriers.
Light-independent reactions (Calvin Cycle) – These occur in the stroma of the chloroplasts and use ATP and NADPH to convert carbon dioxide into glucose.

Transpiration and Water Transport

Transpiration is a critical process for maintaining water flow through the plant. As water evaporates through stomata in the leaves, it creates a negative pressure that pulls water upward from the roots through the xylem in a process known as the transpiration pull.

Plant Hormones: Controlling Growth

Plants use hormones to regulate growth and responses to environmental stimuli:

Auxins – Promote cell elongation and help plants grow toward light (phototropism).
Cytokinins – Promote cell division and growth in the roots.
Gibberellins – Stimulate stem elongation and seed germination.
Abscisic acid (ABA) – Helps plants cope with stress, such as drought, by closing stomata.

Nitrogen is an essential nutrient for plants, as it is a key component of proteins and nucleic acids. However, plants cannot use nitrogen directly from the atmosphere. Certain bacteria in the roots of legumes convert atmospheric nitrogen into forms that plants can absorb and use, a process called nitrogen fixation.

INTERMEDIATE LEVEL: KEY PROCESSES AND FUNCTIONS IN PLANTS