Effects of Sodium Bicarbonate on Photosynthesis - Lab Report Example

Investigate the effects of sodium bicarbonate and light intensity on the rate of photosynthesis of leaves through the observation of floating leaf discs Name: Institution: Introduction During the photosynthetic stages of a plant’s leaf, there are several factors that take center stage, key among them the intensity of light that is absorbed by the leaves. The absorption of the light through the pigments found in the leaves such as the chlorophyll a and b pigments activates the electrons that are found in the leaf’s photosystems thus, boosting the electrons to higher energy levels (Kalman, 2005). Under the same conditions, the photosynthetic process enables the production of ATP, which incorporates the carbon dioxide (CO2) into organic molecules while reducing the NADP to NADPH through the process of carbon fixation. In this experiment, the aim is to investigate on the effects of sodium bicarbonate and the intensity of light on the photosynthesis rate in green spinach leaves through the use of floating leaf disks. Being autotrophic organisms, leaves depend on the photosynthesis process that occurs in a series of enzyme mediated steps to capture light and build energy rich carbohydrates. Leaves, when put under water undergo the light-dependent reaction process, thereby producing and releasing oxygen to their interior parts; thus, causing them to rise. However, during the same process, another process, cellular respiration, takes place and consumes the produced oxygen. Therefore, this implies that leaves must have provided the source of carbon that would allow for photosynthesis to take place (Renger, 2008). The available carbon dioxide coupled with the amount of light that the plant receives, the rate of photosynthesis is influenced. With the aspect of sodium bicarbonate arising from the CO2, it is predictable that the same would have an effect on photosynthesis rate. In this lab report, data shall be presented for the variables of the study in categories of control, dependent and independent variables. The data collected shall be in the form of number of disks that floated during the experiment when subjected under different intensities of light and solutions. Hypothesis The hypothesis is that when the green spinach leaves are exposed to higher light intensities in the presence of the sodium bicarbonate, less time will be taken for the leaf disks to float. This is for the reason that there is an increase in the production rate of oxygen during the photosynthesis process that the leaf disks undergo. Variables a. Control variables: the likely control variables in this study are; i. Temperature, which is determined by the laboratory’s room temperature that was kept constant throughout the experiment in all the solutions. ii. Infiltration solution volume. iii. Spinacia oleracea as the spinach species used. iv. Leaf discs cut into uniform shapes v. Sodium bicarbonate solution. b. Dependent variable: This is the time that the disks take to float to the top of the solutions as is kept and recorded by a standard stopwatch. c. Independent variable: The light intensity, in which the same light source and distance from the setup will be used. Raw data collection Upon setting up an experiment in the recommended manner using all the laboratory materials and procedures, the following data was recorded in relation to the number of leaf disks that float to the top of the solutions at a given time intervals. The experiment engaged four trials with 20 cm CO2 light, 10 cm CO2 light, 10 cm water/soap light and a fourth trial with 10 cm CO2 dark. Trial one and two are similar except for the difference in the diameter of the leaf disks, thus, difference in volumes. The table below represents the attained data for the number of leaf disks that floated overtime in different experimental conditions after a period of 30 minutes. The quantity of leaf disks that float in different solutions and light intensities during photosynthesis The number of floating disks per trial Time in minutes Trial 1 20 cm/CO2 Light Trial 2 10 cm/CO2Light Trial 3 10cm/Water/Soap Trial 4 10 cm/CO2 Dark 1 0 0 0 0 2 0 0 0 0 3 0 0 0 0 4 0 1 0 0 5 0 1 0 1 6 0 1 0 0 7 0 1 0 0 8 0 2 0 0 9 0 2 0 1 10 0 2 1 1 11 0 1 0 2 12 0 1 1 0 13 0 2 0 1 14 1 1 0 2 15 1 3 0 2 16 1 4 0 2 17 2 4 0 3 18 2 6 1 3 19 2 5 0 4 20 2 6 1 5 21 3 6 1 6 22 2 7 1 7 23 2 7 1 8 24 2 8 0 6 25 2 8 0 5 26 2 9 1 4 27 2 9 1 2 28 2 10 2 1 29 1 10 2 0 30 1 10 2 0 Processing this data necessitates the illustration by graphs so as to determine the relationship between the rate of photosynthesis and the intensity of the light and CO2 in a leaf. This involves the use of Microsoft excel graphing techniques. The resultant graph from the same is as shown below. From the above graph, the results of the experiment under different conditions portray different analyses. In the setting up of the experiment, the leaf disks sunk because their spongy mesophyll spaces remained occupied with the sodium bicarbonate solution. Therefore, when exposed to light under same intensity but, in different solutions, the leaf disks indicate different behaviors while undergoing photosynthesis process. The general equation for photosynthesis that guided this experiment is that 2 H2O + CO2+ light → carbohydrate (CH2O) + O2 + H2O In trial one, the number of disks that float at the end of each time interval are recorded at later stages as compared to trial two due to the excess amount of sodium bicarbonate solution applied to the leaf disks. This means that excess CO2 and less oxygen in the leaves would make them heavy, hence, less likely to float easily. The use of the soap solution in trial three is intended to allow for more of the solution to be drawn into the leaf disks by it wetting the hydrophobic surface of the leaf disks. However, caution was taken for the suds which might arise due to the difficulty in quantifying the concentration of the soap solution (Silverstein et al., 2008). Evaluation and conclusion Trials two and four show direct relationships between the time taken to float and the number of leaf disks that float based on the intensity of light and quantity of sodium bicarbonate. Thus, the same have positive slopes as compared to the other trials. High numbers of disks float at around between the 20th and 25th minutes in all the trials indicating that with longer time durations, more oxygen is produced, which through cellular respiration enable the leaf disks to float in the respective solutions (Renger, 2008). The intracellular spaces of the green spinach leaves remained inundated with the sodium bicarbonate solution thus, the sinking. During the sinking, the leaf disks respire due to the consumption of oxygen produced during photosynthesis. However, with photosynthesis taking place, the produced oxygen collects in the intracellular spaces and causes the leaf disks to float again. Leaf disks in the dark in trial four floated due to the light independent reaction of photosynthesis that utilizes the already captured oxygen and high energy molecules to reduce the CO2 to carbohydrates thus, enable the floating. By taking place in the stroma and not thylakoid membranes of the chloroplasts, it uses the ATP and NADPH to convert the CO2 to glucose/sugar. Therefore, the environmental factors of light and oxygen, based on the results of this experiment have a direct effect on the rate of photosynthesis for green plants. The organisms that can thus, undergo photosynthesis are autotrophs such as algae, plants and other bacteria (Silverstein et al., 2008). References Kalman, B. (2005). Photosynthesis: Changing sunlight into food. New York, NY: Crabtree Pub. Co. Renger, G. (2008). Primary processes of photosynthesis: Principles and apparatus. Cambridge: RSC Publishing. Silverstein, A., Silverstein, V. B., & Nunn, L. S. (2008). Photosynthesis. Minneapolis: Twenty-First Century Books. Read More