A seed is the basic unit of a plant. It is a biological component that is composed of the genetic components, the endosperm, and the dispersal system. There are many different types of seeds. Some of them are categorized into a few categories.
The endosperm of a seed is a collection of food stored by the embryo. It contains protein, oils and starch. In addition, it has a tough outer layer called the testa, which protects the embryo. During germination, the cotyledons take over the role of breaking down the stored food material in the endosperm.
Many researchers have examined the structure of the cell walls of the endosperm of seeds during germination. Studies have revealed that the cell wall of the outermost cell bordering the testa is thicker than the rest of the cells. However, some cell walls in the inner layer appeared compressed or uncompressed.
Some of these changes are believed to be caused by the evaporation of water during the freeze drying process. Other studies suggest that the degradation of mannan-type polysaccharides is responsible for the erosion.
Dormancy of seed is a state of seeds that are not able to germinate, due to a number of factors. This condition may occur even under favorable environmental conditions. Its nature and extent depend on the genetic, hormonal and other environmental factors that affect its formation.
Dormancy of seed is an important component of plant fitness. It is beneficial to the health of the species, especially in intact natural systems. In addition, it helps the plant in surviving harsh environments. For example, seeds can be protected from extreme temperatures and water. The presence of dormancy can also help the plants survive in the soil for years.
Seed dormancy occurs when the morphological, physiologic and environmental signals in the seed are not sufficient to facilitate the development of the embryo. Some dormant seeds can also be blocked from sprouting by low levels of growth regulators.
The genetic constituents of seed are complex structures composed of embryo, endosperm, and seed coat. They exhibit an extensive variation within accessions worldwide. Nevertheless, the genetics of seed number and size are still unsolved. Several theories and strategies suggest that selection for these traits can be influenced by life history factors. These include defense against stress, offspring number, and reproductive output.
Genetic factors affecting seed number and size are often subject to trade-offs. These trade-offs can involve direct or indirect effects. However, the magnitude of the trade-off is relatively small. This suggests that the trade-offs may not be as important as they are generally thought.
One approach to identifying genetic factors influencing seed size is to map QTL for the trait. In this study, we mapped nine QTL for the average seed number per fruit.
Germination of seed is a fundamental process in plant development. It includes the development of the embryo axis into a seedling, and also the mobilization of reserves and biochemical preparatory processes. Depending on the species, nutrients and other environmental conditions, seeds vary in their germination process.
The germination of a seed depends on the temperature, light, and the moisture it absorbs. In addition, a seed requires an adequate supply of oxygen. Some seeds do not germinate at all, due to physical or chemical dormancy.
Seed germination is a complex biochemical and physiological process that involves five changes. First, the embryo is activated and begins cell division. Next, the embryo’s axis is elongated. Finally, the radicle emerges. This radicle eventually grows into a root system.
Various mathematical models have been proposed to describe the effects of cardinal temperatures on germination rates. However, many findings in the literature should be reanalyzed.
Seed dispersal is the process of transporting seeds from a parent plant to a new location. The goal of this process is to ensure that germination occurs and that the plant will have a better chance of survival.
Several factors influence the way seeds are dispersed. These factors include the animal or other agent that is carrying the seed, the size of the seed pod, and the shape of the seed.
Animals can carry seeds by passively carrying them, breaking the seed covering, or eating the seed. Some seeds are also sticky enough to stick to animal fur.
Seeds can travel far distances. They can be carried by wind, ocean currents, or other abiotic agents.
Many plants use water to disperse their seeds. Water lilies, for example, have flowers that make fruits that are waterproof. During ripening, the pods split open, allowing the seeds to scatter.