Week8 Draft4

Using the spinach leaves, we extracted the chloroplasts and observed the rate of photosynthesis in various concentrations of water, with a control group in DI water, and two experimental groups- one in tap water, the other in salt water. The rate of the light-dependent reactions was monitored by comparing the absorbance of light in a spectrophotometer at 600 nanometers. As the DCPIP used in the experiment is reduced, the absorbance of light decreases since the first stage of photosynthesis involves the extraction of electrons from water by light energy. Knowing this, if the concentration of water increases within the plant cell, then the rate of the light-dependent reactions should increase as plants require water in the first step of photosynthesis. If our hypothesis is correct, the data would reveal that the chloroplasts exposed to tap water have a significantly lower absorbance over time than the chloroplasts exposed to salt water, where the concentration of H2O is less.