Brassica Rapa Plant

Brassica rapa is an extremely fast growing species of plant, finishing
its life cycle in around 38 days. The plant is a form of turnip with
medicinal properties linking it with the suppression of breast and
skin cancer.

I will grow these plants under conditions where they have all the
nutrients required (the Control) and under conditions where one of the
essential macro elements is absent. The six macronutrients, Nitrogen
(N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg) and
Sulphur (S) are required by plants in large amounts.

The macro elements absent in the different plants in the investigation
are Calcium, Phosphorous, Magnesium and Potassium.

Calcium is an important component of plant cell walls and in the
structure and permeability of cell membranes. The elongation and
division of cells requires Calcium. Calcium aids in the uptake of
nitrogen. Calcium deficiency can prevent the lateral buds and root
tips from forming resulting in reduced growth.

Phosphorous is used in energy transfers and storage in plants.
Adenosine di- and triphosphate are important forms that phosphates
occur in that are involved in the energy transfer processes e.g. from
the cytochrome system in glycolysis. The uptake of nutrients and their
movement through transpiration require these energy transfer
processes. Also, Phosphorous is important as a component of many
proteins, enzymes, and nucleic acids. Phosphorous is a component of
phospholipids which make up most of cell membranes. Phosphorous
increases root growth which allows the plant to take up water and
nutrients at a higher rate. Phosphorous increases rate of flower and
fruit production.

Magnesium is used to produce chlorophyll molecules and is also used in
enzyme activation. Most energy processes involving ATP require
Magnesium. Magnesium is also a component of ribosomes in plants.

Potassium is important as a regulatory molecule in photosynthesis,
energy production, starch synthesis, and protein synthesis. Potassium
is different than the other nutrients since it is not incorporated
into any organic compounds but remains as an ion in the plant. It
forms part of the cytoplasm and helps to lower water loss from the
leaves and increase water uptake by the plants roots. Potassium
increases the growth of tubers and bulbs if they are present in the
plant. It helps improve the plant's disease resistance and lowers the
numbers of insect problems. It increases the strength of the stems and
also improves the colour of leaves and flowers.


Aim

To determine the effects of macro element deficiencies in plants by
investigation.


Summary

All plants but the control should develop some form of deficiency
symptom. Extra quantitative results were taken in relation to water
uptake levels since this information shows aspects of the deficiencies
that cannot be accurately measured such as leaf surface area and root
size/length.

As well as quantitative results, observational results were taken in
the course of the investigation within a log book since these results
are more important than the other results as they deal with aspects
such as colour, leaf death, wilting and degree of branching in root
system.


Hypothesis

My hypothesis is that the plants grown in Calcium deficient solutions
will show stunted growth of stalk and roots as well as the appearance
of curved leaves.

The plants grown in Phosphorous deficient solutions will have very
stunted growth, red/purple bases, older leaves becoming purple and
poor flower growth.

The plants grown in Magnesium deficient solutions will develop thin
etiolated stalks with chlorotic leaves. Some of the leaves will
experience early death or an off-coloured red appearance.

The plants grown in Potassium deficient solutions will have their
older leaves show signs of chlorosis followed by a red appearance on
the edges resulting in death which spreads toward the centre of the
leaf.


Experimental Method

[IMAGE]

Polystyrene cubes used to contain the plants - each cube has four
holes inserted into it to allow space for the soil. A two inch long
piece of felt was fastened to each hole by a needle to keep the soil
in and to allow absorption of solution from a beaker underneath. Holes
were then filled with compost almost to the top (no fertiliser is
added); two seeds inserted in each hole, then another 5mm of compost
was added to this. Ten of these were set up (2 Control; 2 Calcium
deficient; 2 Phosphorous deficient; 2 Magnesium deficient; 2 Potassium
deficient). A Control was also used which has no macro element
deficiencies. The solutions were prepared from a nutrient powder which
is weighed according to the bottle's directions and dissolved in one
litre of distilled water. More of these solutions were made up when
needed, eventually leading to a total of 3 litres of solution being
made up for each plant set. Since the solution was added to a beaker
where the felt reaches the bottom, it did not matter how often the
solutions were topped up, although this was done several times a week.

Each cube is placed on top of a beaker full of solution, so that there
are two beakers, and therefore sixteen plants for each solution. Each
of the beakers has been covered in black tape to prevent algal growth
in the solutions which could give inaccurate results for the
investigation by absorbing some of the nutrients themselves. The
experiment is placed in a light box and elevated to within a few
centimetres of fluorescent tubes that provide warmth, and light for
when seeds sprout. A dropper is used to moisten the surface with
liquid since the movement of water up into the compost is too slow
without the roots of the plants present.

One week later all the seeds have sprouted and have grown a few
centimetres. One plant from each hole is removed to lower competition
(the weaker plant is removed). There is now no need for the lab jacks.
After a few days some of the plants have grown too high and have to be
propped up with sticks and rubber fasteners. Three weeks after
planting, the plants exhibit features of nutrient deficiency.

Many results were taken every 1 to 3 days including plant heights,
internode length, number of flowers appearing on each plant, and
eventually the number of seedpods appearing, were taken over a five
week period. After this time the plants died. All of these factors
vary depending on the (chemical) conditions the plants are in.

I also noted my observational results since some of these cannot be
presented in a numerical form.

After a period of five weeks the plants finished their life cycle and
died, before which all the macro element deficiency characteristics
had appeared in all plants.

During the investigation an additional experiment was set up
consisting of a beaker, covered in black tape, with a polystyrene cube
(without any holes) placed on top. This was then filled with a known
volume of water and left for several days in order to find the rate of
evaporation of water in the given conditions. The surface area of the
water exposed in the beaker was the same as the area of water exposed
in the experiments themselves. I found the evaporation rate to be 4.6
cm³.


Results

Note that day '1' is the first day of actual result taking, i.e. when
sufficient plants have germinated. The result taking process was
delayed slightly due to illness. Also note that the colour of each
heading in the table corresponds to the colour of its respective line
on the graph.

Average Height of Plants (cm)

Day

Control

Calcium

Phosphorous

Magnesium

Potassium

1

1.9

2.75

1.7

3.85

3.5

2

2.6

3

1.9

4.85

5

6

4.75

7.75

4.8

8.15

10

9

11.1

11.5

5.85

13.75

11.9

13

17

11.7

6.75

19.25

16.55

15

18.85

11.7

7.85

20

16.8

16

18.5

11.35

8.4

23.5

16.65

20

20.25

12.9

10.2

23.5

17

23

19.5

12.4

11.75

24

17

29

19.25

12.65

14.5

20.65

17

30

19.25

12.5

14.5

22.5

17.5

[IMAGE]

Average Length of Internode (cm)

Day

Control

Calcium

Phosphorous

Magnesium

Potassium

9

2.35

1.85

0.6

1.9

3

13

3

3

1.9

3.7

3.25

15

3.1

3

3

3.75

3

16

3.1

2.7

3

3

2.9

20

3.6

2.25

3

2.75

3.25

23

2.85

2.35

3.2

3.1

3.35

29

2.75

2.5

2.5

2.75

3.25

30

2.75

2.4

2.25

2.25

3.5

[IMAGE]

Average Number of Flowers on Plants

Day

Control

Calcium

Phosphorous

Magnesium

Potassium

9

6

6

1

5

6

13

18

9

2

17

17

15

18

10

2

18

20

16

11

3

2

3

2

20

2

2

3

6

9

23

5

1

2

1

0

29

1

2

1

9

7

30

0

2

2

10

6

[IMAGE]

Average Number of Seed Pods Appearing on Plants

Day

Control

Calcium

Phosphorous

Magnesium

Potassium

16

7

4

2

18

4

20

14

11

2

16

7

23

16

8

3

25

15

29

15

13

5

23

16

30

20

12

6

18

19

[IMAGE]

Percentage Differences in Height of Plants

Day

Control

Calcium

Phosphorous

Magnesium

Potassium

1

0

+44.73%

-10.52%

+102.63%

+84.21%

9

0

+3.6%

-47.29%

+23.87%

+7.21%

20

0

-36.29%

-49.63%

+16.05%

-16.05%

30

0

-35.06%

-24.68%

+16.88%

-9.09%

[IMAGE]

Percentage Differences in Internode Length

Day

Control

Calcium

Phosphorous

Magnesium

Potassium

9

0

-21.28%

-74.47%

-19.15%

+27.66%

16

0

-13.03%

-3.23%

-3.23%

-6.45%

23

0

-17.54%

+12.28%

+8.77%

+17.54%

30

0

-12.72%

-18.18%

-18.18%

+27.27%

[IMAGE]

Percentage Differences in Number of Flowers on Plants

Day

Control

Calcium

Phosphorous

Magnesium

Potassium

9

0

0%

-83.33%

-16.67%

0%

16

0

-72.27%

-81.81%

-72.72%

-81.81%

23

0

-80%

-60%

-80%

-100%

30

0

+[IMAGE]%

+[IMAGE]%

+[IMAGE]%

+[IMAGE]%

[IMAGE]

Percentage Difference in Number of Seed Pods Appearing on Plants

Day

Control

Calcium

Phosphorous

Magnesium

Potassium

16

0

-42.86%

-71.43%

+157.14%

-42.86%

20

0

-21.43%

-85.71%

+14.29%

-50%

23

0

-50%

-81.25%

+56.25%

-6.25%

30

0

-40%

-70%

-10%

-5%

[IMAGE]

Total Volume of Solution Absorbed by Plant's Roots over 30 Days

By calculation, using the additional experiment described in the
method section, I found the total volume of solution absorbed by the
different plants. Using the rate of 4.6 cm³ a day evaporation from the
beakers, as well as the total volume of solution made up for each
experiment (3 litres) I was able to calculate that each plant absorbed
the following volumes of solution in the 29 days the experiment ran
for. Values are in cm³.

Control

Calcium

Phosphorous

Magnesium

Potassium

2373.6

1428.6

1847.6

2293.6

2176.6

[IMAGE]

Observational Results

The root length was long in both the Magnesium deficient plant and the
Control. The Phosphorous deficient plant had shorter roots while the
Potassium deficient plant had extremely long roots. The Calcium
deficient plants did not ever fully develop their roots during the
experiment. Their roots only showed within the last two weeks of the
experiment.

The Control plant grew as normal, flowered, produced seed pods, then
died once it had completed its life cycle.

The Magnesium deficient plant was much the same, although it became
chlorotic at the later stages of the experiment it still managed to
produce seed pods.

The Calcium deficient plant was weak, grew slowly to a shorter height
without developing its roots properly, and experienced early leaf
death.

The Potassium deficient plant grew to a good height, though slightly
shorter than the Control, and managed to develop its flowers and seed
pods despite its early leaf death and red base.

The Phosphorous deficient plant developed red bases and grew to a much
shorter height than the other plants. In spite of this it still
managed to produce flowers and seed pods.

Conclusion

All plants, as predicted, developed the deficiency symptoms as
outlined in my hypothesis. The volumes of solutions absorbed, given in
the results, give information about the features of the plants. The
Control absorbs most solution since it has developed full and healthy
leaves while the Calcium-deficient plant absorbs the least amount of
solution since most of its leaves have shrivelled and died.

The plant heights and Internode lengths show the Magnesium-deficient
plants to be taller than the Control, showing they are etiolated.

The Calcium, Phosphorous and Potassium-deficient plants are weaker
plants and so do not develop as many flowers and eventually seedpods.
The Phosphorous-deficient plants are much smaller and so this is also
a large factor contributing to this feature.

The observational results also show my hypothesis to be correct. These
results were more important than the quantitative results since these
describe the main plants features such as colour of leaves and whether
plant is wilting or not - these cannot be shown in a graph form, for
example.

Evaluation

There were some inaccuracies in the investigation which could not be
helped. Human error was a factor in all of the results with the
exception of the solution absorbency rates.

1. Lengths of plants/their internodes were hard to obtain with
measuring tape.

2. Solution absorbency rates had inaccuracies in them since the
evaporation rate can change from week to week depending on the room's
conditions (e.g. room was much warmer at end of investigation than at
start since investigation began in winter and finished close to March
when weather was much improved). However these inaccuracies had no
large effect on the results since the conditions of the room were the
same for all plants throughout the investigation.

3. A major problem encountered during the experiment was the
considerable water loss due to the lamps being on 24 hours a day - the
problem was worst at the weekend when there is no way to water them.

The compost used was free of nutrients.

Although some plants from each set-up died in the course of the
investigation, the results were hardly affected since an average of
all other plants was taken and used. No more than 4 plants died from
each set-up so this plant death was not a problem.

Readings for the Internode length were not taken until nine days into
the experiment because all the plants had the same features in terms
of size and appearance up to this point.

Readings for the number of flowers present on each plant were not
taken until nine days into the experiment because up to this point
there had been no significant development of the flowers.

There are significant differences in appearance between the percentage
difference graphs of flowers and seed pods. This was due to the fact
that it was often hard to distinguish between a flower and seed pod
since the pod forms from the centre of the flower. A seed pod was
termed a seed pod when the flower it came from had died.

Acknowledgements

James A. Duke (1983) Handbook of Energy Crops. Visited March 2003.
URL:

http://www.hort.purdue.edu/newcrop/duke_energy/Brassica_rapa.html

Thomas Wallace (1943) The Diagnosis of Mineral Deficiencies in Plants
by Visual Symptoms Visited March 2003. URL:

http://www.luminet.net/~wenonah/min-def/list.htm

Thanks

I would like to thank Mr X and the Technician staff for their great
help during this long investigation.