Download Plant Nutrition: Magnesium and Calcium

Plant Nutrition: Magnesium and Calcium
Carly D. Case
Texas Woman’s University
Abstract
The purpose of this paper is to research plant nutrition, specifically calcium and
magnesium. The paper provides a discussion of the essential elements that plants need in
order to grow and produce properly. In addition, specific plant deficiency symptoms are
also discussed. The paper also contains information on environmental plant stresses.
Environmental plant stresses often lead to a lower production rate which can be very
detrimental to many communities. Examples of environmental plant stresses include:
drought, freezes, heat, salinity, soil mineral deficiency, and soil mineral toxicity. I
personally performed an experiment that examined how calcium and magnesium
deficiencies affected Brassica rapa, a Wisconsin fast plant. I have also included the
message that I would like to get across to my future students in terms of plant nutrition
and the environmental factors that affect them.
Plant Nutrition: Magnesium and Calcium
Section I
Plant Nutrition
Plant nutrition involves an array of raw materials that the plant requires to
function properly. Plants require sunlight, water, and essential minerals within the earth
to carry out their daily functions.
It took hundreds of years for research scientists to determine what elements were
essential for plants growth. Two criterions that must be met in order for an element to be
deemed essential are: the element is needed for a plant to complete its life cycle, if the
element is part of any molecule of the plant, or if the absence of the element produces any
deficiency symptoms even though the plant can produce viable seeds (Eichhorn, Every,
& Raven, 2005). The essential minerals include: carbon, hydrogen, oxygen, potassium,
calcium, magnesium, nitrogen, phosphorus, sulfur, iron, molybdenum, nickel, copper,
zinc, manganese, boron, and chlorine (p. 646). If a plant lacks one or more of these
essential minerals, the plant can display characteristic abnormalities often due to the
inability to reproduce properly. The paper will discuss in thorough detail the following
essential macronutrients: nitrogen, potassium, phosphorus, magnesium, and calcium.
Nitrogen is a multi-functioning element to plant growth. It is a component of
amino acids, proteins, nucleotides, nucleic acids, chlorophylls, and coenzymes (Loomis
& Novoa, 1998). Nitrogen is a very versatile element that plays an important part in
many different plant processes. “Proteins serve as enzyme catalysts in metabolic
pathways, as structural elements of cytoplasm and membranes, and as carriers in
transport functions” (Loomis & Novoa, 1998, p. 1). Nitrogen also plays a part in nucleic
acids. Nucleic acids are very important in processes such as codification, storage, and
translation or genetic material. It is very common for the agricultural soils to be deficient
in the oxidized and reduced forms of nitrogen; the form that plants successfully absorbs
(Loomis & Novoa, 1998). If nitrogen is not present for plants to absorb, plants can
develop chlorosis (Eichhorn, Every, & Raven, 2005). When a plant develops chlorosis,
the leaves begin to turn yellow and eventually tan as they die.
Potassium is important to plant growth because it is involved in osmosis and the
ionic balance. In addition, potassium also has an impact on the opening and closing of the
stomata and it is an activator to many enzymes. Plants that experience potassium
deficiencies often have chlorotic leaves with spots of necrotic tissue present on the
margins (Drew, 1975). Their stems also become very weak and narrow (Eichhorn, Every,
& Raven, 2005).
Phosphorus is important to plant growth because it is the component of energy
carrying phosphate compounds such as ATP and ADP. Additionally, phosphorus plays a
role in nucleic acids, coenzymes, and phospholipids (Eichhorn, Every, & Raven, 2005).
In the absence of phosphorus, a plant becomes dark green, and later they become red or
purple in color because of the accumulation of anthocyanins. Also, the plants experience
stunted stems and their older leaves turning brown in color and dying.
Magnesium is important to plant growth because it is a component of chlorophyll
molecules and an activator to many enzymes (Eichhorn, Every, & Raven, 2005). If a
plant experiences a magnesium deficiency, it will be unable to form the compound that
makes the plant green, which is chlorophyll. Like plants that are nitrogen deficient,
chlorosis can be formed when a plant is deprived of magnesium. According to Eichhorn,
Every, and Raven (2005), magnesium deficiencies are more detrimental to older leaves.
The reason for this is because the younger leaves are able to withdraw the needed
nutrients from the older leaves. The ability for the younger leaves to withdraw the
nutrients depends on the mobility of the magnesium in the phloem (Eichhorn, Every, &
Raven, 2005).
Calcium is important to plant growth for many reasons. For starters, it is a
component of cell walls and calmodulin, involved in cellular membrane permeability,
and a regulator of membrane and enzyme activities (Eichhorn, Every, & Raven, 2005).
When a plant experiences calcium deficiency, their roots and tips die causing the plant to
not be able to grow any longer. One visual distinction that occurs to the plants leaves is
they become hooked.
In conclusion of plant nutrition, it is vital that plants receive all the essential
elements in order to grow to its full potential and reproduce properly. Thus far, I have
explained how detrimental it can be if a plant lacks even one single essential element. It
would be even more detrimental if a plant lacks more than one.
Environmental Plant Stresses
Environmental plant stresses are directly related to the limitations that are seen in
agricultural production. The major environmental plant stresses include: drought, freezes,
heat, salinity, soil mineral deficiency, and soil mineral toxicity (Blum, 2009). In the
following paragraphs, I will touch on drought and salinity issues.
According to Tinker (2010), there is a drought concern through much of the
southern and central plains. Droughts occur due to a long time period where there is no
precipitation or rain. Due to the lack of precipitation, the soil becomes very dry and
undesirable for plant growth. This can be detrimental to plants because they are unable to
survive without water.
Plants that are affected by salinity often grow at a much slower rate than plants
that are not affected (Berstein, 1975). Due to the slow growth rate, these plants have
stunted fruits, leaves, and stems. Their leaves are often a darker green compared to
normal plants.
In conclusion of environmental plant stressors, all of the factors above can limit
agricultural production. If agricultural production decreases, we as humans must find
other means of food to consume. Although we cannot control the environment, many
researchers are in the process of using genetic tools to enhance the production of plants
and food. I am still on the fence as to whether or not this is a solution to the
environmental stressors, but it is a start.
Section II
Plant Nutrition Lab Results: Calcium and Magnesium
I performed an experiment that examined how calcium and magnesium
deficiencies affected the Brassica rapa, a Wisconsin fast plant. I located a control liquid
plant medium that contained all essential nutrients, a calcium deficient liquid medium,
and a magnesium deficient liquid medium. Based upon prior knowledge of the functions
of calcium and magnesium, I made predictions. I predicted that the control liquid medium
plant medium would allow the plants to have a strong stem and green leaves. I predicted
that it would grow the tallest and produce flowers. I predicted that the calcium deficient
liquid medium would begin to grow, but then die towards the end of the experiment. I
predicted that the magnesium deficient liquid medium would allow the plants to grow,
but at a slower rate.
Materials and Methods
I began with 12 Brassica rapa seeds, 6 beakers, 6 planters, and 400 mL of each
liquid medium. I rinsed all beakers with distilled water. I placed split 400 mL of control
liquid plant medium between the two beakers. Then, I split 400 mL of the calcium
deficient liquid medium between two more beakers. I did the same for the magnesium
deficient liquid medium. I then placed 2 seeds in each planter. I placed one planter per
beaker. The planters were submerged into the liquid medium until the seeds were just
covered. Then, I placed the final product into a small greenhouse that had a plant light.
Results
The following tables express the results that I obtained throughout my 22 day
experimental trial.
Brassica rapa in control liquid medium
Stem Height (in.)
Leaf Length (in.)
Texture Color Flowering
N/A
N/A
N/A
N/A
no
1.5
0.5 smooth
green no
3.5
0.75 smooth
green no
4.5
1.25 smooth
green no
4.7
1.3 smooth
green yes;yellow
5
1.5 smooth
green yes;yellow
Figure 1: Brassica rapa in control liquid medium. The data table above expresses the data
Day
1
3
8
15
17
22
obtained throughout the experiment. The stems grew to a height of 5 inches, while the leaf
lengths were 1.5 inches. The plant indicated that it was healthy due to the smooth, green leaves
that it possessed. Flowering was present towards the end of the experimental trial.
Day
1
3
8
15
17
22
Brassica rapa in Calcium deficient medium
Stem Height (in.) Leaf Length (in.) Texture Color
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
light
sprout
sprout
N/A
green
died
died
N/A
yellow
died
died
N/A
brown
died
died
N/A
brown
Flowering
no
no
no
no
no
no
Figure 2: Brassica rapa in Calcium deficient medium. The data table above expresses the data
obtained throughout the experiment. The plant began to sprout on day 8. On day 15, it expressed
yellowing of the small stem and leaf that it possessed. Later, it died completely.
Brassica rapa in Magnesium deficient medium
Stem Height (in.) Leaf Length (in.) Texture Color
Flowering
N/A
N/A
N/A
N/A
no
1.25
0.25 smooth green
no
1.75
0.5 smooth green
no
light
15
2.5
0.75 rough
green
no
light
17
2.6
0.75 rough
green
no
22
3
0.9 rough
yellow
no
Figure 3: Brassica rapa in Magnesium deficient medium. The data table above expresses the
Day
1
3
8
data obtained throughout the experiment. The plant grew steadily. Later in the experiment, the
leaves changed to a rough texture with spots present, as well as turned to a light green/ yellow in
color.
Discussion
For the most part, the experimental results that I obtained were supported by
reliable research. The control group grew successfully, the calcium group had trouble,
and the magnesium group grew at a slower rate.
The control outgrew the deficiency plants. The control had very sturdy stems, as
well as healthy green leaves. Towards the end of the experiment, the plant produced an
abundant amount of small yellow flowers. The leaf texture was very smooth. The
predictions I made were supported by my findings throughout the experiment.
The calcium deficient plants did not do as I had expected. I expected the plants to
grow to a certain point and then wilt away. However, the seeds began to sprout and then
abruptly turned brown and died. According to Eichhorn, Every, and Raven (2005),
calcium deficient plant’s shoot and root tips die. In result, the plant will eventually die. In
the experiment, the plant attempted to grow. I believe that there are two explanations for
why the plant died rapidly. Either the plant was very dependent upon calcium and the
lack of it was detrimental, or the seeds were submerged in too much water.
The magnesium deficient plants grew how I expected. In the beginning, the plants
grew at a steady rate. As they got taller, their steams appeared to be more slender than the
control. Due to their slender stems, they tended to lean in one direction or the other.
Towards the end of the experiment, the leaves appeared to be rougher than the beginning.
They also developed light colored spots. According to Eichhorn, Evert, and Raven
(2005), necrotic spots can form on the leaves.
Overall, the experimental results that I obtained were accurate. The experiment
visually explained how detrimental it is when a plant experiences a deficiency in a single
essential element.
Section III
Message to Students
I would enjoy teaching a plant biology class to students for many reasons. First, I
believe it is important for students to understand the importance of plants. Plants are
important to maintain every part of life. They take in the carbon that is produced in the air
and replenishes the oxygen in which humans and animals breathe. Plants also produce
many of our food sources; whether it’s grass for animals to eat, or vegetables for humans
to eat. Second, it is important that students understand their environment and respect it. It
is important to recycle materials properly instead of putting everything in a land fill.
Landfills put off a lot of gas that the plants must convert into oxygen. Thirdly, it is
important for students to understand the environmental stresses that limit the agricultural
productions.
I believe doing an experiment similar to the one I did would be very beneficial to
students who take a plant biology class. Students will have a lot of freedom with this type
of experiment. They will be able to create their own experimental set up to an extent.
Also, they will be able to create charts and data tables to express their results to the class.
By working in groups, students will be able to use their strengths to peer teach the other
students. For example, some students do not have strong back grounds in creating
computer generated graphs and charts, while others do. The students who do have strong
backgrounds can help the weaker student become more comfortable with the computer
generated charts and graphs. On another note, the students could divide the research
information amongst themselves. This is a jigsaw type approach. Each group member
will become an expert on a specific aspect of the research. Then, they will report back to
each of the other group members to explain their findings. This will help the students
complete this project in a timely manner.
References
Blum, A. (2009). Plant Stresses. Retrieved 15, Dec. 2010. http://www.plantstress.com/
Bernstein, L. (1975). Effects of salinity and sodicity on plant growth. Annual review of
Phytopathology, 13, 295-312
Drew, M.C. (1975). Comparison of the effects of a localized supply of phosphate, nitrate,
ammonium, and potassium on the growth of the seminal root system, and the
shoot in barely. New phytol, 75, 479-490.
Eichhorn, S. E., Evert, R.F., & Raven, P. E. (2005). Biology of plants. New York, NY:
W. H. Freeman and Company.
Loomis, R.S. & Novoa, R. (1998). Nitrogen and plant production. Plant and soil, 50(1),
177-204.
Tinker, R. (2010). U.S. drought monitor. Retrieved 15, Dec. 2010.
http://drought.unl.edu/dm/monitor.html