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What Is a Seed?

seed

Seeds are the primary means of reproduction for flowering plants. They contain a miniature undeveloped plant and food reserves enclosed in protective coats.

Scientists are beginning to understand the genetic controls that determine seed development by studying a model plant, Arabidopsis thaliana. They hope that knowledge of this process will help them understand how seeds evolved from simpler ovules and seeds in gymnosperms to the diversity found in angiosperms.

Definition

A seed is a fertilized ovule that will grow into a new plant given proper growth conditions. It contains an embryo and food reserves enclosed in a protective outer covering or coat. The embryo is surrounded by the seed coat and in some seeds, a tissue called endosperm which serves as the source of nutrients for the embryo during germination.

Seeds are the primary source of many foods, including wheat, rice, soybeans and peanuts. They are also used in medicine, dyes and fuel. Seeds are classified as monocotyledonous and dicotyledonous based on the number of seed leaves, known as cotyledons. Monocots have one cotyledon while dicots have two.

In computer science, a seed is a value that determines a portion of the initial internal state of a DRBG mechanism. The seed must have enough entropy to support the security strength of the DRBG. The term is also used in sports to refer to the ranking and placement of teams or players in a tournament.

Functions

Seeds have several important functions, including storing the embryo of a new plant in a protective outer covering that can sprout under favorable conditions. They also store nutrients for germination.

The inner seed coat is sometimes hard, as in a coconut shell, but it can be soft like a pea or spongy like cotton. This outer layer is known as the testa or tegmen.

A key function of a seed is its ability to survive periods of unfavorable environmental conditions, such as drought or frost. Seeds have a natural dormancy response to ensure this, called physiological dormancy.

This dormancy is triggered by the need for water, oxygen and temperature to be in the right balance for germination. During the process of water uptake, or imbibition, metabolic processes that were suspended or greatly reduced during dormancy resume. This is caused by the action of protein kinases and phosphatases, which are part of a complex system of cell cycle regulation.

Origin

Seeds are one of the most significant innovations in plant evolution. They appear in the fossil record as early as the Devonian. They are the distinguishing feature of a clade of plants called gymnosperms, which are divided into fernlike plants such as cycads and palms and conifers such as pines. A recurrent feature of the gymnosperms is the production of wood from secondary xylem. Another important feature is a system of reproduction called heterospory, whereby each ovary produces two sets of spores.

Seeds come in a wide range of shapes and sizes. Some seeds are large, like those of the coco de mer tree, weighing up to 40 pounds and dispersing by floating in water; others are tiny, such as epiphytic orchid seeds. Seeds also come in a wide variety of colors. Most seeds germinate after a period of dormancy, either physiological (senescence) or photodormancy. Physiological dormancy is broken by cool wet conditions, while photodormancy is broken by light or enzymatic damage caused by ultraviolet rays.

Variation

Seed characteristics, such as seed size and seed number, vary significantly among genotypes within a population. These within-plant variations may reflect diversifying bet-hedging strategies in response to environmental uncertainty (figure 3a). Indeed, several studies have found that plant species with a greater long-term mean seed crop also exhibit higher year-to-year variability in their total seed production.

However, seed traits may also respond to nongenetic factors, such as the condition of mother plants during the vegetative phase of growth. For example, differences in 1000-seed weight and germination percentage (GP) between and within the eight cowpea and 54 mungbean accessions evaluated here suggest that maternal effects play an important role in variation in these seed traits.

Similarly, changes in seed size variation have been correlated with variables other than dispersal syndromes, such as climate, forest structure and life history (figure 4). These relationships are consistent with the hypothesis that shifts in fleshy PTs are more likely to be responses to underlying shifts in resource availability than direct consequences of the evolution of dispersal syndrome.

By Weed Smoker

Rastafarianism is an African religion and there is a great deal of people in the world that follow its teachings. In fact, there are even people that have embraced the lifestyle that is closely associated with Rastafarianism in the past such as musician and entertainer Bob Marley and Rastafarian clothing designer Larry Lloyd.

As the name implies, the Rastafarian lifestyle includes wearing clothes and accessories that are made out of beads, feathers, and other natural materials. The clothing in the Rastafarian tradition often includes animal skin, such as a horse's hide. The hair of the Rastafarian man is also usually long.

The lifestyle of Rastafarians is largely based on traditional ways of living in their native countries, as well as the African traditions and rituals that are passed down. Rastafarians have a great deal of respect for the animals that are part of their diet. Most people that follow this type of lifestyle believe that they have a direct link to the animals that they eat. In fact, in some cases, the animals may be eaten during the ceremony that follows the ceremony.

In addition to having a great deal of respect for the animals, Rastafarians also have a great deal of respect for their hobbies and pastimes. They often dress in clothes that are similar to that of the animals that they eat. Rastafarians also have a great deal of respect for the clothing that they wear and the clothing that is used to decorate their home. The color of the clothing and accessories that are worn by Rastafarians is often very similar to that of the animals that they eat.

Although Rastafarians follow a lifestyle that is based on a natural way of life, some of them do have to be in the workplace. For example, many Rastafarians work as musicians or entertainers. In order to do so, the musician may have to give up some of his or her time in order to become successful. In addition, some musicians choose to work for other musicians, such as Bob Marley and the Wailers. However, other musicians choose to work for themselves, like Bob Marley.

Although the Rastafarian lifestyle is different from that of other people, the Rastafarian lifestyle is also a life of peace and harmony. The Rastafarian people live a simple life where they eat animal meat, live in their own homes, and do not engage in much of the materialistic activities of society.