Pisum sativa

The effect of Pisum sativa seeds germinating while soaked in water for 24 hours, and seeds wrapped in paper towel for an additional 24 and 48 hours on the rate of oxygen consumption (ml/min) as measured by respirometers surrounded by a 25ºC water bath

Research Question:

When three different treatments (T1- germinating pea seeds soaked in water for 24 hours, T2- germinating pea seeds initially soaked for 24 hours and wrapped in a paper towel for another 24 hours, T3- germinating pea seeds initially soaked for 24 hours and wrapped in a paper towel for another 48 hours) of Pisum sativa seeds in respirometers are rested in a 25ºC water bath over 20 minutes, in 5 minute intervals, what will be the effect on the volume of gas (ml) in the respirometers? In addition, how will the rate of oxygen consumption (ml/min) differ between each treatment?

KV: IV1: contents of the respirometer:

T1: germinating pea seeds soaked in water for 24 hours;

T2: germinating pea seeds initially soaked in water for 24 hours and germinating for an additional 24 hours wrapped in moist paper towel

T3: germinating pea seeds initially soaked in water for 24 hours and germinating for an additional 48 hours wrapped in moist paper towel

T4: glass beads to control for volume

DV1: volume of gas (ml) in respirometer over 20 minutes, in 5 minute intervals, for each treatment

DV2: rate of oxygen consumption for each treatment: ml O2/min

CV1: The temperature of the water bath in which all of the treatments will be placed will be kept constant to room temperature (25ºC) when O2 consumption will be measured

CV2: The temperature of the water bath in which all of the pea seeds will initially be germinating in will be kept constant to 25ºC.

CV2: The volume of CO2 produced during cellular respiration will be sequestered as a solid by reacting it with 10 drops of 15% potassium hydroxide (KOH) soaked in the absorbent cotton. A 1cm wad of dry cotton will be added on top of this. The reaction will yield K2CO3 and H2O. The amounts of cotton and KOH must be the same for each respirometer. Because the CO2 is being sequestered, the change in volume of gas in the rspirometer will be proportional t the volume of oxygen consumed.

CV3: The volume of all the contents in the respirometers will be controlled using the water displacement method. T1 will be filled with 50mL of H2O and the volume of water that is displaced is equivalent to the volume of peas. The same will happen for T2 and T3 with peas that wrapped in a paper towel and germinating for 24 and 48 hours. Enough content will be added to attain a volume equivalent to that of a

CV4: The ambient changes in atmospheric pressure will be controlled by Treatment 4 (beads only). Changes in volume of gas in these treatments will determine the changes in gas volume of the other 3 treatments. This will be controlled by using the difference in the change in ambient pressure of other respirometers and the change in Treatment 4 as a correction.

CV5: time: 0 to 20 minutes, in 5 minute intervals, over which respirometer gas volume is measured. The readings of the water's position in each pipette must be recorded.

Hypothesis:

The relationship between the period of time that pea seeds have been germinating for and the rate of cellular respiration will be a positive, linear relationship. That is, as the number of hours that each set of pea seeds is allowed to germinate for increases, respiration rate will increase too. Pea seeds that were only allowed to germinate for the first 24 hours in the water bath will have the least oxygen consumption rate. Pea seeds that were initially allowed to germinate for the first 24 hours in the water bath with an additional germinating time of 24 hours while wrapped in a moist paper towel will have the second most oxygen consumption rate. The last set of germinating peas, those that were initially soaked in the water bath for 24 hours and are allowed to germinate for an additional 48 hours while wrapped in a moist paper towel will have the greatest oxygen consumption rate.

After seeds fall from their plant and go into a state of dormancy, they wait until the right time arrives for them to germinate. Those seeds that have begun germinating for a while will require more oxygen in order for them to grow and survive than those that are dormant or have just begun to germinate. By doing cellular respiration, seeds are allowed to acquire the energy needed to grow. As seeds begin to or continue to germinate, more and more cells are developing and these cells require energy. The cells therefore, undergo cellular respiration, in which the presence of oxygen, the last electron acceptor, is crucial to the electron transport system. For this reason, those pea seeds that have been germinating for 48 hours after a 24 hour soak in water, will consume the most oxygen for all the increasing cells to respire. Because pea seeds only soaked in water for 24 hours are not germinating for as long, their cells do not require as much oxygen.

The relationship between the volume of gas in the respirometer and the pressure in the respirometer will be a negative, linear relationship. This is because the volume of oxygen consumed will eventually be reduced and solidified. KOH will remove the CO2 respired during respiration. The change in the volume of CO2 produced in the respirometer will be proportional to the volume of oxygen consumed. During the experiment, there will be tiny changes in in pressure within the respirometers placed inside the water bath. Differences are due to the ambient changes in atmospheric pressure. The water in the water bath will move into the pipette where there is lower pressure. This is because the pressure created by water is more than that created by air, so the water must move inwards. These tiny amounts of pressure will be measured in order to see where a difference is made. Treatment 4, containing just beads (same volume as contents in other respirometers) is a control for measuring changes in the atmospheric pressure.

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