The Affects of Iron and Magnesium Deficiency on Lemma minor’s Photosynthetic Process

Lucia Aguilar

INTRODUCTION

Photosynthesis is the process in which plants can convert light energy into chemical energy to fulfill all of the functions of life. Iron and magnesium are nutrients that play an important role in photosynthesis. Deficiency in either of these nutrients will lead to a change in the photosynthetic rate of plants such as Lemma minor (duckweed). Magnesium is a mobile nutrient that affects older plants before it affects younger plants. Iron is a fairly immobile nutrient that causes chlorosis, the yellowing of leaves due to inadequate amounts of nutrients, in the younger plants (Campbell and Reece, 2005)

In this experiment with variable deficiencies of magnesium and iron in Lemma minor, magnesium and iron nutrient concentrations were varied to see what affect the concentration variation, away from the required, had on the rate of photosynthesis of Lemma minor. It was hypothesized that a lack in either magnesium or iron would cause a disruption in the rate of photosynthesis. It was hypothesized that deficiency in magnesium would cause the Lemma minor to be unable to reproduce in number and therefore result in a lower dry mass. The cause of this would be the magnesium’s characteristics of being mobile. Because the magnesium is mobile, the photosynthetic properties of the older plants will be the first to be affected resulting in an inadequate amount of energy which is needed to allow for offspring. The deficiency in iron will cause chlorosis in the Lemma minor due to its ability to affect the younger leaves resulting in the decrease in the photosynthetic rate.

METHODS

1. Collect Lemma minor from the Joliet Pond

2. Different concentrations of nutrients labeled A-I (ten for each) in small cups

3. Place 10 Lemma minor per cup nutrients and 100mL of corresponding solution

4. Allow one week of photosynthesis with nutrient concentration

5. Count number of yellow (chlorosis) Lemma minor in each concentration

6. Allow Lemma minor to grow one more week in the different nutrient concentrations.

7. Repeat Step 5

8. Collect Lemma minor from each cup and place into separate envelope

9. Allow to dry for one week in the oven

10. Count and weigh dried (grams) the samples from each cup

11. Use the SPSS to analyze data

RESULTS

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Figure 1: Comparison of the 0. 0, 0.001, 0.002 magnesium concentration as compared to the same concentration of iron at the 95% Confidence Interval observed during the first week of the experiment.

There is a significant difference between the high (0.002mol) and low concentration (0.0mol) of magnesium when iron is at its lowest (0.0mol) and mid (0.001mol) concentrations. When iron is at its highest there is no significant difference between the low and high concentrations of magnesium. At the mid concentration (0.001mol) , there is a significant decrease in the amount of the live duckweed present (0.0mol) when iron is at its highest compared to the low (x=17, 95% CI, Figure 1) and high concentrations of magnesium (x=17, 95% CI, Figure 1). A trend was visible because at the 0.002mol concentration of iron, the max death rate of the duckweed is seen in the 0.001mol of magnesium. At the high concentration of magnesium found in the 0.mol concentration of iron, it was equal to the low concentration of magnesium found in the 0.001mol of iron.

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Figure 2: Comparison of the 0.0, 0.001, 0.002 magnesium concentration as compared to the same concentration of iron at the 95% Confidence Interval observed during the first week if the experiment.

At the lowest concentration of iron there was no significant difference observed between any of the magnesium variation. The same was observed between the magnesium concentrations at the mid concentration of iron. There was however, a significant difference observed between the magnesium concentrations when the concentration of iron was at its highest (x=0, respectively at 95% confidence interval, Figure 2). The max death rate occurs at mid concentration of magnesium but no significant difference between high and low. There was however a significant difference between 0.001mol and 0.002mol of magnesium compared to the low concentration of magnesium at the 0.002mol when iron is at its highest (x=0.002. As the concentration of iron increased, the magnesium with the highest concentration also increases showing a significant difference.

Discussion

Week one demonstrated that a high concentration of iron had a similar growth rate when combined with the high and mid concentration of the magnesium. There was a significant difference in week when between the highest concentration of iron and the mid concentration of magnesium due to all of the duckweed dying for reasons unknown. The duckweed might have died inside of the cups due to s contaminated container (Figure 1). As expected, the zero iron concentration had the lowest number of plant growth in the magnesium concentration (Figure 2) when week one and week two were compared, it was obvious that the higher iron concentration slowed for more plants to arise. It was supported that the growth rate would decrease in the cups containing the lowest concentration of nutrients (Figure 2). Both weeks (Figure 1 and 2) rejected the idea of a sufficient amount of nutrient leads to an appropriate photosynthetic rate. In the cups deficient in iron, our hypothesis was supported because there was a large amount of duckweed that had undergone apparent chlorosis and resulted in low dry weight. In the future a wider range of nutrients should be used to fully understand their individual and group part in photosynthesis.

WORK CITED

Campbell, Neil and Jane Reece. 2005. Biology: Seventh Edition. Pearson: San Francisco.