Plant growth and development

The Seed and Germination

Seeds are a way of reproduction in plants, containing an embryonic plant covered by a protective outer covering.
Germination happens when a seedling begins to grow, requiring available water, a suitable temperature, and favourable light conditions.
The seed’s coat softens and splits in reaction to water, allowing the embryonic root to break through, and the leaf and stem follows.

There are various stages of plant development including germination, seedling growth, vegetative development, reproduction, and senescence.
During seedling growth stage, the plant develops initial leaves to begin photosynthesis on its own.
After vegetative development, the plant enters a reproductive stage where flowers, fruits, and seeds are formed.
Senescence is the final stage of a plant’s life cycle, often characterised by yellowing leaves and reduced metabolic function.

Photosynthesis is the process by which green plants convert light energy, usually from the sun, into chemical energy in the form of glucose.
Photosynthesis occurs mainly in leaf cells, specifically in the chloroplasts where chlorophyll (a green pigment) absorbs sunlight.
The general formula of photosynthesis is: 6CO2 + 6H2O + light energy = C6H12O6 + 6O2.

Just like animals, plants also produce hormones known as phytohormones for coordination and regulation of growth and development.
There are five main groups of phytohormones: auxins, gibberellins, cytokinins, abscisic acid, and ethylene.
Examples of their functions include controlling the direction of growth (auxins), promoting cell division (cytokinins), and facilitating plant ageing (ethylene).

Plants require different nutrients for growth, including macronutrients (e.g., nitrogen, phosphorus, and potassium) and micronutrients (e.g., iron, zinc, and manganese).
Nutrients are primarily absorbed through the roots and transported within the plant through the xylem.
Water is crucial for plant life, aiding in important functions like photosynthesis, nutrient transport, and temperature regulation.

Plants have several adaptations to cope with different environmental conditions like drought, high salinity, or low nutrient availability.
Some desert plants store water in their tissues (succulence) and minimise water loss through a thick cuticle and small, sunken stomata.
Some plants living in nutrient-poor soils can trap and digest insects to supplement their nutrient intake, these are known as carnivorous plants.