Jennifer Sarmiento 12/2/17
Internal 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).
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.
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.
BARLEY: Origin, Botany, Culture,
Winter Hardiness, Genetics, Utilization, Pests. (n.d.). Retrieved December 2,
2017, from https://naldc.nal.usda.gov/download/CAT79716376/P
Brouwer, 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
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.