Jennifer Sarmiento 12/2/17BSGE 11-1Internal Assessment Part 1:Question: What is the effect of salt concentration on the seed germination of Barley (Hordeum vulgare)?Background Information: In order for a seed to germinate, there are multiple stages that it goes through.
First through imbibition, the seed takes up water, causing the seed to swell and soften. This is a necessary step in order for the interim or lag phase to occur, in which the seed start to respire and go through life processes such as food metabolism and synthesis of proteins. Once the cells in the seed start to divide, the root and radicle sprout from the seed, which from there, the seed develops into a seedling, starting to sprout leaves as the root continues to receive enough water and nutrients (Stivers et. al). Typically, seeds are vulnerable to many factors that could prevent the seed from going through imbibition or developing into a seedling such as salt (NaCl).
Under saline conditions, seeds require higher amount of water uptake during germination, since the accumulated amount of salt, a soluble solute, increases the osmotic pressure (Demir et. al). This means that the seed will not only be prevented from absorbing water due to the high solute concentration surrounding the seed, but it instead will also uptake a great number of ions from the salt, which can be toxifying for the seed. Studies have shown that a high ion content in a plant cell causes changes in protein hydration which restrains enzyme activity, impairs DNA synthesis and also interferes with mitosis, all of which can be harmful as the necessary life processes are being restrained (Waisel, 1972).
However, there are plants that are more immune and tolerant to salts as they have been more exposed to salts and have adapted to these conditions. These plants are called halophytes, and they in comparison to glycophytes—or the non-salt tolerant plants–deal with the high concentrations of salt in various methods, one method being able to rupture and release the salt back into the environment. One example of a halophyte plant is Barley (Hordeum vulgare) that is a member of the grass family (Poaceae) and it is known for having a high level of salt tolerance.
Barley (Hordeum vulgare) is able to withstand a salt concentration up to 10 g/l, which is considerably more than sensitive crops who can only withstand 2.5 g/l (Brouwer et. al). Furthermore, Barley tends to grow well in cool, dry areas, however it can grow in a hot climate, but is more susceptible to diseases and pathogens (Weibe, 1979).
Despite this, Barley is sensitive to low temperatures and will die if the temperature is below 17°F. To continue, Barley grows well between a pH value of 6.0– 8.
5 (Weibe, 1979).Statement of Personal Interest: I find this experiment interesting because I want to find out the effectiveness of barley when dealing with salt. Since I was younger, my mom was always interested in growing plants and crops, having a skill for always keeping her plants healthy and beautiful. However, I was not the same, mainly because I was not informed of the different growing conditions of plants. This experiment will allow me to continue learning about this, and expand my knowledge on halophytes.Independent and Dependent Variables: The independent variable in this experiment is the concentration of salt in the water for the Barley seeds. This variable will be varied in the mass of salt, which will be measured in grams, which will be applied for the water amount, which will be kept constant at 10 ml. There will be one group in which the salt concentration will be 0 and the other groups will gradually increase in salt concentrations, up to a concentration of about 15 g/l.
The dependent variable is the seed germination of Hordeum vulgare. This can be measured by counting the amount of seeds that are germinated after 3 days. This then can be converted into a germination percentage by calculating the amount of seeds that germinated divided by the total number of seeds times 100.Controlled Variables:Water content: The volume of water that each seed will be placed in will be at 10 ml in the petri dish.Temperature: The seeds that will be germinated will be placed in a place at a temperature of 25 degrees Celsius. Light: All the seeds being germinated will be placed in a place where the same amount of light is hitting the petri dish.The space between each seed germinated: This space will be kept constant at 2 inches of space between each seed.
Hypothesis: It is predicted that as the salt concentration in the water increases, the seed germination of Barley (Hordeum vulgare) will decrease, decreasing at a faster rate once the salt concentration is higher. Since, under saline conditions, seeds require higher amount of water uptake during germination, since the accumulated amount of salt, a soluble solute, increases the osmotic pressure (Demir et. al). This means that the seed will not only be prevented from absorbing water due to the high solute concentration surrounding the seed, but it instead will also uptake a great number of ions from the salt, which can be toxifying for the seed.
This will then lead to a restraint in enzyme activity, impair in DNA synthesis and mitosis, affecting the necessary life processes are being restrained (Waisel, 1972). However, since Barley tends to grow in a drier area, its germination rate is predicted to not be as low in comparison to other plants, since it does not need to absorb as much water as other plants. This means that the Barley seed is not as likely to absorb as much of the ions from the salt, which decreases the chances of the Barley seed to be impaired in the life processes in comparison to other plant seeds. BibliographyBrouwer, C., Goffeau, A., & Heibloem, M.
(1985). Introduction to Irrigation (Provisional ed.). FAO Land and Water Development Division. Demir, I., & Mavi, K. (n.
d.). Effect of salt and osmotic stresses on the germination of pepper seeds of different maturation stages. Retrieved December 02, 2017, from http://www.
scielo.br/scielo.php?script=sci_arttext&pid=S1516-89132008000500004 Wiebe, G.A.
1979. Introduction of barley into the new world. In: Barley: origin, botany, culture, winter hardiness, genetics utilization, pests. USDA Agriculture Handbook 338. Washington, DC.
Stivers, L., & Dupont, T. (2017, November 13). Understanding Seeds and Seedling Biology. Retrieved December 02, 2017, from https://extension.
psu.edu/understanding-seeds-and-seedling-biology Waisel, Y. (2012). Biology of halophytes (1st ed.
). Burlington: Elsevier Science.