The Seeds Structure The outer and visible part of a seed is called the seed coat. It protects the embryo from harm, injury, and drying out. The seed coat has three layers: The thicker layer, tough "stony" or middle layer, and the inner layer. The endosperm is a temporart food supply tissue, that accumulates starch, protein, and fats. It is for the seed while it is germinating, packed around the embryo in the form of special leaves, cotyledons, or seed leaves. This is generally the first part visible while the seed germinates. Plants are classified upon the number of cotyledons, seed leaves, in the seed. Monocots contain one cotyledon as Dicots have two cotyledons. Immediately inside the cell wall is the nucellus. It is a peper like layer surrounding the megaspore cell wall. Inside the megaspore cell wall is the megagmetophyte, the female gametophyte, the haploid mutritional tissue found in gymnosperm seeds. In the development of cones, the megagamentophytes makes egg cells which are fertized by male gametees to produce zygotes. The zygotes develope into the embryos. The megagametophyte then plays its second functional role. It surrounds the embryo, protecting and nourishing it. The embryo is located in the corrosion cavity, a pit in the center of the megagametophyte that is fully filled by the embryo in mature seeds. It is the cotyledons, shoot apical meristem, room apical meristem, root cap and suspensor. Pointing towards the wider chalazal end of the seed are the shoot apical meristem and cotyledons. After you have a dormant embryo, a storage tissue, and a seed coat, then you have the seed. The Seed's Needs The germination of seeds is very complex believe it or not. It is a physiological process that is started when it has enough oxygen and water, which then lets out any of the possible dormancy mechanisms by certains triggers depending on what seeds. Under the required weather and temperature of the soil, the embyo breaks and "explodes" the covering layers of the seed and emergence of the radicle, which is considered as the completion of germination. If the soil temperature is extremely low or too high, the growth of the seed is effected. It will either slow down the germination process, or the germination process is entirely stopped, meaning the seed will not germinate. Most germinations don't follow through correctly or at all due to the cause of soil depth the seeds are at. Small seeds are recommended to be planted on the soil's surface and pressed or rolled in for best results due to they contain a limited amount of stored food for a limited period of time during the growth. When the seed germinates, it must immediately sprout out from the soil and began to produce its own food as quickly as possible. Seeds too deeply buried beneath the surface of the soil will not germinate properly. They may use up the food supply they have to reaching the soil surface, causing their death before there is life. They may also sufficate cause by the lack of oxygen from being so deeply buried, causing no germinations altogether. Other reasons the seed will not germinate is due to the amount of water. Too much water in the soil pushes the air out, causing the seed to rot. Not enough water will cause the delicate seed to dry out and die. Temperature wise, aslo affects the outcome of the seed. Depending on what seeds depend on the radiation needed to start germinating. Too low of a temperature, the seed will take up water but will not be able to germinate and therefore, also rots. Too high of a temperature will prevent the growth of the seed. UV Light History Ultraviolet Light, also known as UV light, or sometimes Black light, was found shortly after the the 1800s some time during year 1801. The 'dark ortion' of the solar spectrum, the UV light, waws discovered by the German physicist, Johann Wilhelm Ritter and was named 'ultra violet' radiation. UV Light Information Ultraviolet light has shorter wavelengths than visible light. Ultraviolet Light is invisible electromagnetic radiation between visible violet light and X rays. The ultraviolet radiation in sunlight is divided into three bands: UVA (320-400 nanometers) that can cause skin damage and may cause melanomatous skin cancer. UVB (280-320 nanometers), stronger radiation that increases in the summer and is a common cause of sunburn and most common skin cancer. Then there is UVC (below 280 nanometers), which is the strongest and potentially most harmful form of ultralight radiation. Most of the UVC and much of the UVB radiation is taken by the ozone layer of the atmosphere before it can even reach the earth's surface. The effect of this, results increases the amount of ultraviolet radiation that can pass through it. Koning, Ross E. Seeds and Seed Germination. ESCU University. 1994 N/A. Seed Germination Database.Thompson & Morgan Successful Seed Raising Guide. N/A. N/A. Seed Germination. N/A. N/A. Dr. Gerhard Leubner. The Seed Biology Place. 24 January, 2003. N/A. Forest Biology Course Site - Foresty 200.N/A ask jigar about this ::: http://www.blacklite.com/History/History_Main.htm
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