When seeds wake up from their dormant state, they need water, air and warmth to sprout. This is called germination, and it’s the first step to turning a seed into a plant.
Within a seed is an embryonic plant that includes the root, stem and leaves (called cotyledons). They all need food from the endosperm until they can absorb it themselves through photosynthesis.
What is a seed?
A seed is a fertilized ovule that contains a plant embryo and a food reserve called endosperm. These are essential to the development of a new plant.
A seed can be of many different shapes, sizes, colours and textures. These are all determined by the species of plant it comes from.
Usually, seeds are shaped like a kidney (reniform), bean-shaped or ovate with lobed ends on either side of the hilum. They can also be ellipsoid, globose or subglobose.
Most seeds are dormant at first, resting inside their coat until they can get the right conditions to grow. Some have special features that allow them to disperse in the wind, water or through the soil. Some have fleshy appendages that attract animal dispersers, like ants.
How does a seed grow?
Seeds are the tiny parts of plants that grow into larger plants. They are made of an outer shell called the seed coat, a plant embryo with a root and leaves, and some plant food for the plant embryo, called endosperm.
To start growing, a seed needs water, the right temperature and light to germinate. When it germinates, a sprout forms and this grows into a small plant.
In the beginning, a seed must soak up water (called imbibition) which causes the seed coat to swell and split open. This lets the plant food that is inside the seed to flow out into the air and soil.
Then, a little shoot emerges from the seed that has a root called a radicle and the first two leaves known as cotyledons. As the plant starts making its own food, it uses these leaves to absorb sunlight and turn this energy into carbon dioxide and water in a process called photosynthesis.
What is the difference between a seed and a seedling?
Seeds are the embryonic cells of a plant encapsulated in a protective outer covering. This outer coating is called a seed coat.
In a flowering plant, seeds are derived from ovules that have formed from the pollen grains of female flowers. These ovules contain an embryo sac and eight nuclei.
These nuclei each carry a set of chromosomes. Some plants have haploid nuclei and others have diploid nuclei.
Seeds are generally larger than seedlings, and they grow slower. Most vegetable seeds take 2 to 3 weeks before they sprout, and seedlings usually germinate in just a few days.
What is the purpose of a seed?
The purpose of a seed is to provide food, fiber and fuel for living organisms. Staple crops, such as cereals and legumes, contain the majority of calories consumed by humans, and many foods such as fruits and vegetables, oils, spices and beverages can also be derived from seeds.
Almost all plants have a reproductive structure called an ovule that produces a seed when pollen lands on it and is fertilized. In angiosperms, the ovule is protected by a hard or fleshy seed-enclosing structure called a fruit.
A seed coat protects the ovule and embryo and usually holds some initial nutrition, often called endosperm. The outer coat varies from thin and papery to rock-hard.
