Seeds are the primary means by which most angiosperm (flowering) plants disseminate their offspring. They contain a reserve supply of food that gives the new plant an excellent start in life.
While extensive studies of “model” plants like Arabidopsis have revealed many genes involved in ovule and seed development, much remains unknown about the genetic control of seed structure and growth in non-model plant groups.
Definition
A seed is a mature fertilized plant ovule with an embryo enclosed in a protective seed coat. It is the principal means by which angiosperm plants disseminate offspring. Seeds are also the source of many important crops, such as grains and legumes, which provide food for people and animals. Seeds are also the source of cooking oils and spices, and they are an important source of protein in diets.
Other meanings:
[1]in the field of botany, agriculture and horticulture, a vegetative or reproductive plant part that contains an embryo under a dormant state and can develop into a new plant if it is sown. This term is sometimes used more generally to describe any living organ of a crop in rudimentary form that is used for propagation.
In the verb senses, seed is often used figuratively to mean the starting point for something: The idea was seeded in my mind by an article I read. It is also used to arrange the drawings for positions in a tournament so that superior players or teams will not meet in early rounds of play: to seed (a tournament).
Functions
Seeds serve several functions for the plants that produce them. Key among them are nourishment of the embryo, dispersal to a new location and dormancy during unfavorable conditions.
Most seeds have a protective outer covering known as a seed coat. This can be as thin as a coconut shell or very hard like that of a pine tree. It also has an opening called the micropyle or hilum and a ridge or groove on its surface called the raphe.
The raphe provides a way for water to enter the seed during germination. The permeability of the seed coat and the amount of water available determine how fast the embryo imbibes water and initiates germination.
Physiological dormancy, which is the natural state of most seeds, delays germination until environmental conditions are optimal. This function helps to safeguard the seeds from a catastrophe like cold weather or herbivory that could wipe out all of an embryonic plant population.
Structure
Seeds store the genetic information needed for a plant to grow and produce more seeds. They are protected by a shell or husk and they contain a reserve of food to sustain the embryo until conditions are right for growth (dormancy).
A seed is made up of three parts: an embryo, endosperm, and a seed coat. The embryo is fertilized ovule that has the potential to give rise to a new plant under favorable conditions. The endosperm is a nutritious tissue that is derived from the integument of the ovary or fruit wall. The seed coat is a hard protective covering that can help seeds survive for long periods of time.
The cotyledons, or seed leaves, are attached to the embryonic axis, either one (Monocotyledons) or two in dicots. The area above the point of attachment of the cotyledons is called the epicotyl and ends in an apical meristem, which will become the shoot of the plant upon germination.
Dispersal
Plants need to disperse their seeds so that they do not grow too close and compete for water, light and nutrients. Seeds are dispersed by wind, animals or water.
Many plants produce edible fruits and nuts that act as containers for their seeds. These seeds are then hitchhiked on the backs of birds, mammals and other animals, and are carried to distant locations by the animal’s movements. The seeds have hard coatings that prevent them from being digested, and hooks and barbs which cling to fur or feathers or the hair of animals.
Other seeds are dispersed by wind. Some seeds have wings that allow them to fly, while others are propelled by the force of air currents. For seeds that are wind-dispersed, the distance they travel is influenced by landscape features and weather conditions. Seeds that are dispersed far away from the parent plant have higher germination rates because they do not suffer competition with parents or siblings, avoid exposure to pathogens and predators, and have better opportunities to colonise new habitats.
