To accomplish this, the plants were subjected t different light colours (Blue, Green, Red and purple). Plants can carry out both photosynthesis and respiration simultaneously. We did this by using a Gilson Respirometer and samples of Elodea plant placed in H2O and NaHCO 3 solutionsâboth of which were operated under lighte d and darkened external conditionsâto measure the consumption of CO 2 during photosynthesis and the production of CO 2 during respiration. By Rookie Parenting Science Updated 10/29/2020. In this lab, students will be testing whether or not aquatic plants do photosynthesis in the dark or light, and also testing if they do cellular respiration during the dark or light. During photosynthesis, plants are using the energy of the sun to build molecules which effectively store this energy (glucose). algae Elodea. ADVERTISEMENTS: Expt. 3. To demonstrate this we will determine whether CO 2 is consumed or produced as elodea (anacharis) is placed in either a light or dark environment.