EXPERIMENT 2 : GROWTH AND DEVELOPMENTTITLE : STRUCTURE OF SEEDOBJECTIVES : 1. To study the structure of seeds2. To determine the presence of nutrients in germinating seedsAPPARATUS AND MATERIALS :1. Balance2. Dishes3. Razor blade4. Test tubes5. Test tube rack6. Beaker7. Bunsen burner8. Microscope9. Tap water10. Green bean seed (dry)11. Soaked green bean (soaked for 24-48 hours)12. Soy bean (dry)13. Soaked soy bean (soaked for 24-48 hours)14. Benedicts reagent15. Iodine solution

PROCEDURE :1. An amount of dry green beans, soaked green beans, dry soy beans and soaked soy beans were put in beakers (each beaker contains about 10 seeds). Then they were weighed on the balance, and the weighs were recorded.2. A piece of dry green bean was observed to study its structure. To view its structure clearly, it was observed under the microscope. Then the structure observed has sketched.3. Step 2 was repeated for dry soy bean.4. A piece of wet green bean was then observed with the naked eye, then using the microscope.5. After that, the seed coat of the wet green bean was removed, and the plumule, redicle and cotyledon of the seed were noted.6. Step 4 Step 5 was repeated for wet soy bean.7. All for types of seeds were cut using the razor blade at the thin section of cotyledon. Then, each section of the seeds was tested using the Iodine solution and Benedicts reagent in test tubes.8. Test tubes containing Iodine solution and the seeds were left for about 20 - 30 minutes, while for test tubes containing Benedicts solutions and the seeds were put in beaker containing heated water, and also left in that hot temperature for 20 - 30 minutes.9. The changes of the seeds after being tested were recorded.RESULTS :1. Mass of the seeds :SeedsDry Green BeanSoaked Green BeanDry Soy BeanSoaked Soy Bean

Mass (g)0.640.722.022.47

2. Results of Iodine and Benedict Test :Green BeanSoy Bean

DrySoakedDrySoaked

Benedicts Solution Test negative Positive Light green seed turns to dark green seed negative Positive Pales yellow seed turns to dark green seed

Iodine Solution Test Positive Light blue-black presence at some parts of the seed Positive The blue-back colour covers the whole seed Positive Dark red colour covers the whole seed Positive Dark red colour presence at some parts of the seed.

DISCUSSIONS :This experiment was carried out to first, study the structure of seeds. Green bean and soy bean were used throughout the experiment. Both seeds used were in dry form, and soaked form. For the soaked form of seeds, they should be soaked in water for about 24 - 48 hours before the experiment carried out. After the structure of the seeds had studied by observing them with naked eyes and by using microscope for clear observation, they were then stained in Iodine solution and Benedicts solution.While observing the seeds, there are many structures that had been identified; as shown on the sketches in the results. However, of all the types of seeds that had been observed, the tiny hole that seeds should has, called the micropyl, it can only seen on the dry soy bean, after observing it under the microscope. Since the hole is very tiny, it was very hard to identify the micropyl. The hole is actually the pathway for the plumule and radicle to grow when the seeds start to develop.Besides that, the dry seeds and the soaked seeds had showed some differences. The very obvious different between the two types of seeds is their coating and their hardness. Soaked seeds had wrinkled coating, and softer in texture, making their coat easy to be taken out and easy to split the cotyledons. Compared to the dry seeds, they are harder in texture. Same goes to their coat, they almost cannot be taken out. To split their cotyledons, a razor blade was needed, and this needs to be handled with a full concentration and care, to avoid injuries.On the other hand, the plumule of the soaked green bean had identified after taking out its coat and split the dicotyledons into two. The plumule located at where the cotyledons are attached. The seed has not really grown up, but this observation shows that the seed was started to grow. The structure looks like a pair of leaf. Plumule is a collective name for the epitocyl, young leaves and shoots apical meristem.Next, to answer one of the questions in the Laboratory manual, after testing the seeds by staining them in the Iodine solution and Benedicts solution to test the presence of starch and reducing sugar respectively, the outcome of the test was slightly against the theory for the Benedicts test. Theoretically, the outcome for both tests should be as shown in the table below;SeedsGreen BeanSoy Bean

DrySoakedDrySoaked

Benedicts solution TestPositiveNegativePositiveNegative

Iodine solution TestPositivePositivePositivePositive

When compared to the results of the experiment, the seeds which showed no reaction to the Benedicts Solution are dry green bean and dry soy bean. While the soaked green bean and soaked soy bean showed a positive reaction with the Benedicts. This shows that the results of the experiment carried out against the theory. This may caused by some error. Such of the errors is; the seeds had been soaked for shorter time that it should be soaked. Besides that, they had taken out from the hot water in a rush. The Benedicts solution and the nutrients in the seeds, especially the reducing sugar had not reacted completely.On the very beginning of the experiment, the seeds had weighed all of them. This is to compare the weight between dry seeds and the soaked seeds. Obviously, the soaked seeds had greater mass than the dry seeds. This shows that water had been absorbed by the seeds. Therefore, the mass of the seeds had increased slightly.For the development and growth of seeds, they need nutrients including water. As the basal cell of the zygote continues dividing, it eventually produces a thread of cells called the suspensor. The suspensor functioned to anchors the embryo with the parent plant. Furthermore, suspensor also acts as the root for the transfer of nutrients from the parent plant to the embryo, and from the endosperm for some species of plants.Seeds are protected against harm by its seed coat. The coat that had removed is the seed coat. The seed coat originated from an unfertilized ovule. The structure of the unfertilized ovule that eventually derives into seed coat; consists of outer testa and inner tegmen is the layered integuments. By the time mitotic division of the nuclei completed, the cell has grown to many times its original volume. At the same time, two outer layers of cells ovules differentiate; that is integuments then forming seed coat.Back to the Iodine test and the Benedicts test, they were used to test the nutrient content of the seeds; in this experiment the presence of starch and reducing sugar. Iodine solution was used to test for the presence of starch. Iodine reacts with starch. The test shows a positive outcome when the reaction produces a purple-black or blue-black on the seeds. In addition, the intensity of the colour produced decreasing with the presence of water miscible. While for the Benedicts test, it tests for the presence of reducing sugar. Examples of reducing sugars are monosaccharide, disaccharide, lactose and maltose. Positive outcome of the reaction will obtain a red precipitate, or green precipitate, or yellow precipitate. This shows that reducing sugar present. However, if no one of the precipitates obtained, this concludes that there is no reducing sugar in the seeds.Lastly, the advantage of using the seeds being in a dried-out state is this state keeps the seeds dormant happily. Compared to the seeds lying on the soil, these seeds get a continuous supply of nutrients, including water, which eventually will break this dormancy. This shows that why is it necessary for the seed to absorb water before it can germinate. Specific condition is necessary to break dormancy. One of the factors that can break this dormancy is the continuous supply of water. As the dormancy had break, the seeds can start to germinate.As a conclusion, dry seeds and soaked seeds have some obvious differences in structures. This is caused by the supply of water, which eventually wakes up the sleeping seeds (dormant). The seeds supplied with water can be seen starting to germinate. The nutrient content in the seeds, such as starch and reducing sugars also differ from each other.CONCLUSION :1. Seed coat, micropyl, radicle, cotyledons and plumule are the features of seeds identified.2. Starch present in all types of seeds, while reducing sugar present in soaked green bean and soaked soy bean.REFERENCES :1. Campbell, BIOLOGY Eight Edition, Pearson Education, Inc.2. INTRODUCTION TO PLANT BIOLOGY, Collins3. www.seedbiology.de 12th Disember 2011