Rate of photosynthesis in leaf disk PDF

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lab report on rate of photosynthesis...

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Rate of photosynthesis in spinach (Spinacia oleracea) Name- Mansi Mansi Date- 8 March 2019 Partner- ‘Gurinder Kaur’ Course- BIOL1210 Section- S07 Instructor- Neilab Amiri

Introduction The purpose of the experiment is to measure the rate of photosynthesis using the leaf disk assay and to examine the effects of sodium bicarbonate concentration on the rate of photosynthesis in leaf disks. Photosynthesis can be defined as the synthesis of organic substances with the use of light as a source of energy. Sunlight is converted to chemical energy by plants and stored as chemical energy in sugar and other molecules (Reece e.t.al,2014). 6C02 + 6H2O  C6H12O6 + 6O2 (Reaction for photosynthesis) In this process, water oxidizes to give oxygen and the amount of oxygen produced can be used to measure the rate of photosynthesis. To conduct this experiment, air from the intercellular spaces of the leaf disks need to be removed using a syringe and the spaces are filled with the liquid solution. After the air is removed, the leaf disks will sink. The liquid solution will be providing carbon dioxide to the leaf disks and as photosynthesis takes place oxygen starts accumulating the intercellular spaces (Hill e.t.al,1985). The time (sec) required by leaf disks to float to the surface will be the measure of photosynthetic rate. The liquid solutions in this experiment will be water used as a control and treatment group will be the baking soda (sodium bicarbonate) with different concentrations in water (0.4%, 0.7% and 0.9%). Water provides less amount of carbon dioxide thus; sodium bicarbonate will be added to water which provide more carbon dioxide in different quantities to measure rate of photosynthesis at different concentrations. The null hypothesis is the different concentrations of sodium bicarbonate (0.4%, 0.7% and 0.9%) will have no effect on the rate of photosynthesis (sec) in leaf disks of Spinach leaves (Spinacia

oleracea). The alternative hypothesis is that different concentrations of sodium bicarbonate (0.4%, 0.7% and 0.9%) will have an effect on the rate of photosynthesis (sec) in leaf disks of Spinach leaves (Spinacia oleracea). We predict that the rate of photosynthesis will be affected by change in sodium bicarbonate concentration. It is expected to increase with increase in concentration as the carbon dioxide in the solution increases with higher amount of oxygen produced at the end of reaction. Reference: Williams, H. (2013, March 08). AP Photosynthesis Lab. Retrieved from https://prezi.com/ 505xyb4vtzo4/ap-photosynthesis-lab/ Materials and Methods: This experiment was performed with modifications as described in the Biology 1210 lab manual (Faculty of Science and Horticulture [FSH], 2019). To test the effects of sodium bicarbonate concentrations on rate of photosynthesis (sec) in leaf disks of Spinach leaves (Spinacia oleracea), liquid solutions were prepared with different concentrations of sodium bicarbonate in distilled water (0.4%, 0.7% and 0.9%). The control was distilled water and the solutions prepared were taken as the treatment groups. For each treatment, three replicates were performed by taking ten leaf disks in a syringe for each replicate and adding 2-3 ml of the sodium bicarbonate solution into the syringe. Partial vacuum was created in the syringe to remove air from intercellular spaces of the mesophyll tissue in leaf disks.

The rate of photosynthesis was measured by keeping the leaf disks in the sodium bicarbonate solution under the lamp. The time(sec) taken by 50% of the leaf disks to float on the surface gave the photosynthetic rate. The mean ( ´x ) rate of photosynthesis ( ´x =

∑ (x−´x )

2

/n-1), variance (S=

∑ x /n ¿

, standard deviation (S2=

s ) √ S 2) and 95% confidence intervals (C.I.= ´x ± 2.0 √n

were calculated to determine if there was noticeable difference in the photosynthetic rate in leaf disks of spinach with different concentrations of sodium bicarbonate. Results: The rate of photosynthesis (sec) in Spinacia oleracea increased as the sodium bicarbonate content in the water increased (Figure 1). The mean rate of photosynthesis was highest in the 0.9% sodium bicarbonate solution, at 543.3sec

± 123.6 and decreased to 596.7sec

± 155.3

at 0.7% sodium bicarbonate concentration (Table 4). The mean photosynthetic rate was lowest at 0.4% concentration (690.3sec

± 141.3) (Table 4).

Table 1: Time(sec) required for 50% of leaf disks to float in water containing different sodium bicarbonate concentrations (%)

Replicate 1 2 3 Mean ( ´x ¿

0.4% 420 600 610 543.3

Sodium bicarbonate concentration (%) 0.7% 0.9% 500 748 540 550 750 773 596.7 690.3

Table 2: Calculation of variance of data for rate of photosynthesis (sec) at different sodium bicarbonate concentrations (%).

Replicate 1 2 3 ∑ (x−´x ) 2 S2= ∑ (x−´x )

0.4% 15202.9 3214.9 4448.9 22866.7 2 /n-1 11433.4

Square of deviations from the mean (x- ´x ¿ 0.7% 0.9% 9350.9 3329.3 3214.9 19684.1 23500.9 6839.3 36066.7 29852.7 18033.4 14926.4

2

Table 3: Calculation of the standard deviation for each treatment group.

S2 S

Calculating standard deviation (S= 0.4% 0.7% 11433.4 18033.4 106.9 134.3

√ S 2) 0.9% 14926.4 122.2

Table 4: Calculation of the 95% confidence intervals for each treatment group.

Sodium bicarbonate concentration s ´x ± 2.0 √n Upper confidence limit Lower confidence limit

Calculating the 95% confidence interval 0.4% 0.7% 0.9% 543.3 ± 123. 596.7 ± 155.3 690.3 ± 141.3 6 666.9 419.7

752 441.4

831.6 549

Table 5: Mean and 95% confidence intervals for control and treatment groups.

800 700

Rate of photosynthesis (sec)

600 500 400 300 200 100 0 Control

0.40%

0.70%

0.90%

Sodium bicarbonate concentration (%)

Figure 1: Mean rate of photosynthesis (sec) in leaf disks of spinach leaves (Spinacia oleracea) and 95% confidence intervals at 0.4%, 0.7% and 0.9% sodium bicarbonate concentrations and at distilled water (control).

Discussion: The objective of this experiment was to determine whether the rate of photosynthesis (sec) differed in leaf disks of spinach leaves (Spinacia oleracea) with sodium bicarbonate concentrations ranging from 0.4% to 0.9%. The results of our experiment show that we fail to reject the null hypothesis which states sodium bicarbonate concentration (%) will have no effect on the photosynthetic rate (sec) in the leaf disks of spinach leaves (Spinacia oleracea). We reject

it because the 95% confidence intervals of the 3 treatment groups (0.4%,0.7% and 0.9%) overlap with each other. Some of the previous experiments tell us that rate of photosynthesis is not affected by sodium bicarbonate concentration which might have occurred because of decrease in light intensity and the by-product oxygen is produced in less amount (MasterDangerPanther9720). One main source of error in this experiment was that the leaves in the solution which were prepared earlier were exposed to some light which affected the time as the photosynthesis started earlier in those solutions. Human errors like time recording and contamination of solution can be reasons for the results. Some other variables were the distance and intensity of light: the cups with solution may have been placed at unequal distances from lamp. In addition, biological variation between spinach leaves may affect the results and photosynthetic rate. Future studies may benefit from using spinach leaves of similar age from same plant to reduce variation. Further research can include more replicates per solution as it can give a broader scale for conducting experiment and treatment groups can be ranged at more levels. Time should be recorded accurately for proper results. Overall, we expected sodium bicarbonate concentration to have an impact on the photosynthetic rate, with higher concentration resulting in higher rate of photosynthesis. The results support the null hypothesis that sodium bicarbonate concentration will not influence the rate of photosynthesis. Our results do not match our original prediction: rate of photosynthesis was higher in leaf disks with more concentrated solution of sodium bicarbonate and lower in leaf disks with less sodium bicarbonate concentration.

References Faculty of Science and Horticulture. (2019). Biology 1210: Introduction to Biology 2 (Spring 2019 ed.). Surrey, Canada: Kwantlen Polytechnic University Bookstore. Guy L. Steucek, & Hill, R. (1985). Photosynthesis: I: An Assay Utilizing Leaf Disks. The

American Biology Teacher, 47(2), 96-99. doi:10.2307/4447960 MasterDangerPanther9720. (n.d.). The alternative hypothesis of this experiment is rejected as the results. Retrieved from https://www.coursehero.com/file/p1qi4q6/The-alternativehypothesis-of-this-experiment-is-rejected-as-the-results/ Reece, J. B., Urry, L. A., Cain, Michael L. (Michael Lee), Wasserman, S. A., Minorsky, P. V., Jackson, R., . . . Wilson, K. E. (2014). Campbell biology: Jane B. reece, lisa A. urry, michael L. cain, steven A. wasserman, peter V. minorsky, robert B. jackson, fiona E. rawle, dion glenn durnford, christopher D. moyes, sandra J. walde, kenneth E. wilson (Canadian ed.). Don Mills, Ontario: Pearson Canada.

Williams, H. (2013, March 08). AP Photosynthesis Lab. Retrieved from https://prezi.com/ 505xyb4vtzo4/ap-photosynthesis-lab/...