Seed Physiology Seed Dormancy Dormation is a delay in growth for a certain period, this condition is found in seeds, shoots, tubers or rhizomes. These plant parts remain variable, but there is a reduction in metabolic activity and this is closely related to external factors and factors internal. Water, light and temperature are external factors that are very influential in causing dormancy to occur. Factors that influence dormancy include the presence of certain compounds that act as inhibitors, in this case including ABA. In seeds, the embryo has not yet reached morphological maturity due to insufficient nutrition, which is also one of the factors that can cause dormancy. This temporary inability to grow is divided into two types: - Kwisen (quisent), namely the inability to grow because the external conditions are not suitable - Dormancy is defined as the inability to grow from seeds because the internal conditions are not suitable, even though the external conditions are suitable. Dormancy in seeds is often caused by the hard seed coat which inhibits them absorption of water and oxygen, naturally dormancy will be broken after fungal attacks on the hard seed coat or after being digested by burns and may also be eroded after being exposed to water flow. The dormancy caused by the hard seed coat can be overcome by certain treatments such as using certain chemical compounds such as alcohol, fat solvents, sulfuric acid or hot water. Apart from that, certain hormones such as GA are also used.3or by scarification, namely sharpening the seed coat. Seed Germination Seed germination is greatly influenced by two main factors, namely internal factors and external factors. Internal factors are factors that originate from within the seed itself, such as whether there is a dormancy period, maturity of the embryo, availability of food reserve sources and the presence of growth hormones that stimulate or even inhibit seed germination. External factors are environmental factors that greatly influence seeds to germinate, such as water availability, temperature, humidity, light and so on. Experiment a. Seed Dormancy Breaking Objective: 1. Overcoming dormancy in seeds caused by the hard seed coat 2. Examining the effect of chemicals and physical factors on germination Materials and tools: Plant material : types of plants with hard-shelled seeds, tobacco seeds Chemical material : : 3 ml of 40 mg/l coumarin solution, 3 ml of 0.5% thiourea solution and distilled water Tools : 9 petri dishes, straw paper, file or whetstone, The lights are white, the plastic is red and blue Ways of working: A. Hard seed coat 1. Prepare 3 petri dishes filled with 2 sheets of damp straw paper (with enough distilled water) 2. Select 6 seeds that are still good, then treat them as follows: a. File or sharpen the 2 seeds at the ends that are far from the embryo, until the cotyledons are visible b. Soak 2 seeds in freshly boiled water and leave until the water cools c. Soak 2 seeds in cold distilled water for 1 to 2 hours 3. Place each group of seeds in one of the available petri dishes, label them according to the treatment given, store them in a dark place at room temperature. 4. Check every day for 7-10 days and note the progress. Compare one treatment with another. B. Chemical treatment 1. Provide 3 petri dishes, each with 2 pieces of straw paper 2. Place 50 tobacco seeds in each petri dish 3. Add in: a. Cup 1: 3 ml distilled water b. Cup 2: 3 ml coumarin solution 40 mg/l c. Cup 3: 3 ml 0.5% thiourea solution 4. Label each cup and store in a dark place at room temperature 5. Observe germination, determine the germination percentage after 72 hours C. Physical treatment 1. Provide 3 Petri dishes, each with 2 pieces of strawberries and 3 ml of distilled water, so that the strawberries are quite damp. 2. Prepare a dark room with dim white lights 3. Place into each cup 50 tobacco seeds 4. Wrap 2 petris each in red and blue and leave one petri unwrapped in colored plastic. 5. Place it in a room with white lights set to 12 hours of light/12 hours of darkness. 6. Determine the percent germination of seeds in each cup after 72 hours Experiment b. Effect of Inhibitory Substances on Seed Germination Objective: Looking at the effect of inhibitory substances contained in fruit flesh on seed germination Materials and tools: Plant material : rice seeds or other types, juice of various types of fruit Tools : Petridis, straw paper Ways of working: 1. Prepare fruit juice from several types of fruit according to the assistant's instructions 2. Make 6 groups of rice seeds of 100 grains each and put them in a petridise without filter paper. 3. Two groups of seeds were germinated in the first fruit juice, 2 groups in the second fruit juice, and 2 groups in distilled water as a control. 4. Every day the fruit liquid is replaced with a new one, but before replacing, the seeds are washed until clean. 5. Observe when the seeds start to germinate and how many seeds germinate each day and determine the percentage of seeds that germinate. Observations were stopped after the control germinated 100% and the percentage of sprouts for the treatment was calculated. 6. Any seeds that germinate after being counted must be discarded at each observation.