| Explore | Plants during photosynthesis need a water source, ample nutrients, and specific soil conditions. To transport water through the plant, first water must diffuse through the root tissue and then travel intercellularly through the differentially permeable membranes of the plasmodesmata until reaching the vascular tissue. Once in the vascular tissue, capillary action and cohesion tension must work together to draw the water up the stem and out of the leaves. When learning about plant cells in class, the body cells of the plant in a hypotonic solution (hypotonic meaning there is more water on the outside of the cell wall) will remain full of water or turgid. This is an essential part of the structure of the plant. How does salinity, pH, and overall qualities of the solution affect the plant? What are some techniques we can use to bend the stalk? |
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| Research Question | During our botany lab, we spent several weeks looking at the cells of plants, identifying their structures and key components. In one of the labs, water relations, we discussed how membranes are selectively permeable to molecules, moving by the process of osmosis of which a solute moves from high to low concentration along a concentration gradient. In this lab, we are interested in manipulating the conditions in which a celery stalk is placed to bend the stalk into a circle whilst maintaining its relative structure and turgidity. |
| Predictions | Originally our prediction was that when placing a celery stalk in a salt-based solution (Soy sauce; hypotonic) would bend the stalk without compromising its structural integrity. We thought that when using soy sauce it would provide enough salt concentration to cause the cells to decrease in overall turgidity whilst giving the stalk nutrients in the form of sugars among other things. For our second trial when testing different pH levels, we predicted that a weak acidic solution would give us the desired effect. We thought that an acidic solution would break down some of the structural elements that the stalk is made of instead of damaging the cells. |
| Experimental Design | Trial 1 1. Prepare 100 ml of 5, 10, and 15 percent (v/v) soy sauce solution in 250 mL beakers. Three replications for each concentration. 3. Prepare 9 20cm long celery stalks by removing leaves and base of the plant. 4. Record the mass, dimensions, and qualities of the stalks. 5. Take photos and make cross-sectional tissue slides of each stalk. Record the percent of cells plasmolyzed in each sample and tissue areas of soy sauce concentration. 6. Insert the ends of a celery stalk into each of the prepared solutions. 7. At 1 day intervals repeat steps 4 - 6 for 3 days. 8. Using collected data make graphs comparing the mass, dimensions, and percent cells plasmolyzed of the salt and soy sauce solutions. Trial 2 1. Prepare 50 mL of Sodium Hydroxide (pH 9), sodium bicarbonate (pH 8.3), water (pH 7), vinegar (pH 2), and lemon juice (pH 3) in 250 mL beakers. 2. Prepare 6 20cm long celery stalks by removing leaves and base of the plant. 3. At six hour intervals take photos and record the overall quality of the stalks. 4. Once the optimal solution is determined to place the pliable celery stalk into a six inch circular petri dish to form it to the desired shape. 5. Waiting another six hours, put the bent celery stalk into a four inch beaker further shaping the stalk. 6. At one hour intervals, gradually decrease the size of the beaker until the stalk bends into a full circle. |
| Conclusion | In our first trial we were quickly able to determine that a sodium chloride based solution would not be able to bend the celery stock. This solution was deficient for two reasons: 1) the solution did not travel to the upper portion of the stalks, and 2) the sodium in the solution caused the cells to plosmolyze even at the lowest of concentrations. We knew from previous experience that salt had a negative affect on plant tissues, but we figured if we used dilute solutions we would be able to minimize the affect, which was, however, not the case. Our next thought was to experiment with solutions containing different pH values ranging from weak acid to weak base with a water control. No affect was visible for the first 6 hours in any of the solutions and the stalks remained relatively firm. After 12 hours , the stalks in the basic solutions showed no signs of bending and only had a slight give when pressed between the fingers. The acidic solutions, however, especially the lemon juice, showed definite signs of bending and had much more of a give. At this time we decided to put the stalk in the lemon juice into a round container to begin the bending process. After an hour we were able to bend the stalk into the desired circular shape. We could reason that the citric acid in lemon juice may have a decalcifying affect; calcium, being a key structural component of plant cells, could explain why the acidic lemon juice was able to bend the stalk whilst not affecting the cells themselves. On the pH scale, our hypothesis that an acidic solution would be best at bending the stalk was supported by our collected data. We could further test acid solutions do determine the precise pH level that best accomplishes the bending process |
| Investigation Theme | CEL |
| Grade Level | Undergraduate Students |
| School Name | Emporia State University |
| Session | Fall 2018 |