A seed is an embryo of a new plant enclosed within a protective outer covering. It consists of an ovule and its endosperm, which is a food reserve that contains nutrients such as starch, oil, and protein.
A thick seed coat protects the embryo from sunlight and water loss. It also prevents entry of parasites into the seed.
Origin
Seeds are a key innovation in the evolution of plants. They have many advantages over spores, like having a food source to feed the new plant and having a protective coat that keeps the seed in place.
Despite their important role in evolution, there is a lot we don’t know about how seeds came to be. This article aims to fill in some of those gaps and explore the origins of seed plants.
The first seed plants emerged around 370 million years ago, during the late Devonian period. During this time, three major trends were crucial to the development of seed plants: heterospory (the production of specialized haploid female-like megaspores and male-like microspores), evolution of the integuments, and the transition to water-independence in pollen formation.
Function
A seed is a tiny plant, containing the embryo of the parent plant. It also contains a food supply for the seedling, called endosperm.
A high quality seed is free of stones, debris, and dust and should be uniform in size, weight, color, and texture. It should also be a healthy, viable plant that produces good yields in the field.
A seed is the reproductive body of most flowering plants and some gymnosperms, including conifers, cycads, ginkgos, and junipers. Seeds have a wide variety of functions and interact with the environment in complex ways. These include multiplication, perennation (surviving a long period of stress such as winter), dormancy, and dispersal. They are essential for biodiversity and help maintain ecosystem balance, protect water resources, and make medicines.
Dormancy
The duration of seed is an important aspect of its life cycle. The seed must break dormancy in order to germinate.
This can be done through many different factors including water, temperature, sunlight, and nutrients in the soil. Once these ideal conditions occur, the seed breaks dormancy and germinates into a seedling.
Dormancy is important for survival because it helps seeds withstand harsh weather conditions while waiting to become a tree or plant. It also allows plants to thrive in environments that would be unfavorable if all seeds germinated at the same time.
In addition, seeds can adapt to the environment by changing their sensitivity thresholds (the depth of dormancy). These thresholds change over time as a response to temperature and other environmental signals.
Germination
Seed germination is the process by which seeds become new plants. It requires the right internal and external conditions – these include oxygen, water, temperature, light or darkness.
Many plants have specific optimum conditions for germination and these vary from plant to plant. The conditions for germination are also closely related to the ecological conditions in a plant’s natural habitat.
For example, some seeds need to go through a process called dormancy before they can germinate. They may need to spend time under certain environmental conditions, such as cold temperatures or fire.
Dispersal
Seeds are a vital component in the survival of many plant species. Without them, plants could not spread out from their parent plant and avoid competition for resources such as light, water and nutrients.
As a result, plants have developed numerous dispersal mechanisms. These include wind, animal or water-based means of transporting seeds and fruit.
For example, many plants enclose their seeds inside edible fruits that are attractive to animals. These fruit-loving animals, called frugivores, can eat the seeds and then pass them along in their faeces.
Some birds and mammals can serve as primary seed dispersers, while others, such as raptors, are thought to act as secondary dispersers. These interactions are called “diploendozoochory” and may have significant ecological significance. However, research is needed to understand these relationships better and assess their impact on seed viability.
