Bulb B Experiment

In this experiment, onion bulbs were placed into different concentrations of caffeine after five days of normal growth in water. Bulb A acted as a control and was kept in the water. Bulb B was placed in a 0.1% concentration of coffee, bulb C was placed in a 0.3% concentration, and bulb D was placed in a 0.5% concentration. After three days in their respective concentrations, the onion roots were cut off, dyed, and placed under a microscope. Finally, the observer counted the number of cells in each phase of the cell cycle to determine the rate of mitosis in the caffeine treated roots. For bulb A, it was found that the average length of the roots grew consistently at about 4 cm per day, until decreasing by 2 cm on the last day. About 36% of the cells in bulb A’s roots were observed to be undergoing mitosis. For bulb B, the average length of the roots began by growing about 34 cm between days 2-5 in water, to growing only 1.4 cm between days 1-3 in

In this experiment, the original bulb C was faulty and did not grow any roots, even in the same conditions as the other three onions. This defective bulb caused the data for bulb C to be a day behind, as it had to be replaced with a new onion that did not start growing until a day after the others. This also meant that its growth was stunted by caffeine at a different stage which may have changed results even more. Another experimental error in this lab is the problem with overlapping cells. When the onion roots were smashed to be viewed under the microscope, some of the cells were overlapping. This could have caused the observer to mistake two overlapping cells as one cell that is in telophase/cytokinesis. This error may consequent in there being too high of an amount for cells in mitosis, and cause the observer to conclude that the caffeine caused a faster rate of root growth because there were more cells undergoing