Today, I am going to explain about seed germination. The resumption of active growth of the embryo resulting in rupture of a seed coat and emergence of a young plant is called as germination. There are three stages of germination. One is pre germination. Second is germination and third one is post germination. In case of pre germination, first the high rehydration takes place that is imbibeation of water. RNA and protein synthesis is stimulated. Increased metabolism that is increased respiration takes place. Later the hydrolysis of reserve food material by the enzymes will be done. Then change in cell ultra structure will be seen. Then induction of cell division and cell growth will be seen. And in case of germination, the rupture of seed coat, emergence of seedling usually radical will be the first. Then post germination, controlled growth of root and shoot axis and then controlled transport of material from food stores to growing axis is seen. Then sentences are aging, sentences of the food storage tissues will be seen. There are three phases of seed germination. One is imbibeation phase. Second is latent phase and exponential phase growth. In case of imbibeation phase, water is absorbed by the seed which activate the gibbalic acid synthesis. This increased gibbalic acid synthesis will internally to increase in DNA synthesis which led to the RNA synthesis or transcription which finally led to the production of amylase enzymes or other hormones or other enzymes also. Which this amylase enzyme will degrade the starch, convert into sugar, this sugar enter inside the epicortile which led to the growth and germination of the seed. Lament phase is further divided into phase 1, 2 and 3. In phase 1, rapid uptake of water takes place and the onset of mRNA synthesis will start. Then the onset of starch degradation takes place. Then glycolysis and fermentation of starch hydrolysis which led to the cell wall biosynthesis non-functional protein degradation, mitochondrial assembly and amino acid biosynthesis. Then in phase 2, that is TCA cycle where in phase 2, coliaptyl emerges emergency. Emergence will be seen then starch biosynthesis, stalking protein degradation and then aerobic respiration will be seen in the phase 3. In the exponential growth phase, the seed code will broke up and then the sugar produced by the aerobic respiration will be consumed by the embryo and epicortile and radical and the hypochortile will start to grow and that will lead to the germination of the seed. There are two types of germination. One is hypogeal germination and another one is epigel germination. In case of hypogeal germination, the cotillidane is present inside the ground level after germination of the seed. That is why it is called as hypogeal germination, hypochial germination inside the ground level. So hypogeal means inside the ground level. This type of hypogeal germination is seen in monocort plants. In case of epigel germination, the cotillidane will come above the ground level after the germination. That is why it is called as epigel. Epigel means above the ground. So this type of germination is seen in case of dikecots. Requirements of germination. First is the light. Generally, seed required darkness to germinate, but sometimes it required light. Photoblastic. If a seed responds to light for germination, named as a photoblastic. Three categories of photoblastic seeds are there. One is positive photoblastic, that is let use or tobacco or some of the examples, which require exposure of sunlight. Whereas negative photoblastic here example is ony and lily amaranthus and they do not require exposed sunlight. Non photoblastic here non exposure of light is needed. Phytocrome is a plant pigment found in cytoplasm that sends the presence of light, that is red light. Phytocrome absorbed light into inter convertible form. PR is metabolically inactive and absorbed red light, that is 660 nanometer. PFR is metabolically active and get transformed into PR. The later promote the germination, that is PR will promote the germination and other phytocrome control, the process of the plant. PFR revert back to PR after absorbing far red light or 730 nanometer. This is the light spectrum, where you can see that the nanometer for red light is from 650 to 760. This is the wavelength in nanometer in function of phytocrome system will be explained in this picture. Here the inactive form that is PR, that is phytocrome with absorbed the red light at 660 nanometer will be converted into active form which is PFR. That will lead to photo morphogenesis. Whereas when this PFR, when it is in active form, the lead to a dark light and it will be produced into, I mean it will be converted into a inactive form. Now this PFR will absorb the far red light at 730 nanometer and converted into PFR which is an inactive form. So usually in this table, you can see that whenever a red light is given to the seed, it will germinate. When you give a red light plus far red light, no germination will be seen. In the same way, if we give red light, far red light and then the red light, germination will be seen. In the same way, if you see here, whenever the last light which will be given in red form, then germination will be seen. Whenever there is a last treatment will be far red light, then there will be a no germination. So we have to remember in this way, when there is a red light, see germination takes place when there is a far red light at the light treatment, then no germination will be seen. To germinate, seed must require, must take in water. Uptake of water by seed is called imbibeation. The imbibeation lead to swelling and breaking the seed coat. Next is oxygen. Eration. Oxygen is required initially for metabolic activity, metabolic activity, breakdown of stored food for energy, radical emergence from the seed coat with aeration. Temperature. Most seed go through cold period before germination. It helps prevent seeds from sprouting as soon as they mature. Most common annual vegetable have optimal germination temperature between 75 to 90 degree Fahrenheit, that is 24 to 32 degree centigrade. Temperature must be optimum. If the temperature is very high, then seed will emerge very fast and even, whether traditional carif crop are soon in June and July after the Resiptoff, Mansoon, West. I mean, Southwest Mansoon, whereas, a rubricop during the October, November. Since seeds are not provided with adequate condition like water, temperature or air for germination, that is seeds in storage form. Dormancy. Seeds remain un germinable, even though provided with suitable condition, then it is called as dormancy.