Effect of Heat Stress on Beetroot and Pea Plant Cell Membranes, Lab Report Example

Introduction

Both the pea plant and the beetroot are exposed to environmental changes that have the ability to alter their cellular components.  The cell membranes are responsible for protecting the cells of these plants.  The cell membrane is described as selectively permeable; allowing certain substances to move in and out of the cell.  When the cell membrane’s ability to function properly is disrupted by chemical, physical, or extreme temperature changes what specific properties of the cell are affected?

One of the most distinguished characteristics of the beetroot is its color or pigment. This pigment is located deep within the cells of the plant in the cell vacuole and is called anthocyanin. This deep purple-red color is contained within the membrane of the vacuole and held in tact by the cell membrane.  If destroyed, these membranes would likely leak this pigment to its surrounding area.  Therefore, this color drainage from the root can be used as an indicator to determine at which point the cell’s protective membrane is no longer able to carry out its natural function.

In an attempt to understand the impact of this temperature increase on beet membranes, samples of the root will be heated at different temperatures while submerged in water.  A control sample of the beet root will be used as a means of comparison.  Under normal circumstances, the control sample would be expected to produce little no color change in the surrounding water.  As a function of the cell membrane, the bilayer forms a hydrophobic (water resistance) lipid barrier that prevents the mixing of water based solutions.  This allows the cell to maintain its homeostatic state.  On the other hand, samples of the root which are heated would be expected to leak their natural betacyanin as the cell membrane loses its ability to maintain its natural state under such extreme circumstances.

The pea plant’s characteristic bright green pigment, also referred to as chlorophyll in the plant cells would be expected to change as a result of heat stress. Contained within the chloroplasts of pea plant cells, the chlorophyll aids in the process of photosynthesis by absorbing and transferring light energy in the cell.  In addition to change in color of the peas, heating would likely change the texture and appearance.  Like the beetroot, the cell membrane of the pea plant would not be able to withstand extreme heat and discoloration and leakage of this green chlorophyll would like be observed.  In the absence of a cell membrane, surrounding water would likely diffuse inside the pea plant penetrating the internal structure of the cell.  This might result in a wrinkled looking soft pea.  As the concentration of water inside the pea plant grows the peas outer shell is stretched to accommodate the water influx.

If samples of beetroot and pea plants are exposed to high temperature extremes, cellular function is compromised.  Pigment leakage will result as the cell membrane’s protective barrier is destroyed.

Methods

1 beetroot/ 3 pea plant leaves

Scalpel

8 22 mL test tubes

Heating plate

Gloves/Goggles

Thermometer

Tweezers

Stopwatch

Test tube rack

Labeling pencil

4 250 mL beaker

4 petri dishes

Ruler

Pour 10 mL of distilled water into 4 22 ml sized test tube

 Using a ruler, cut 4 1 cm by 2 cm pieces of beetroot plant and place each piece in their own test tube of 10 mL distilled water.

 Label each test tube “Sample 1-3,” and leave one test tube as “Control Sample”

Place each pea plant on a petri dish labeled “Sample 1-3” leaving one as the “Control Sample”

Measure and record the temperature of the “Control Sample” water using thermometer for beetroot

Using the heating plate, heat 100 mL of distilled water contained in 250 mL beaker to first measurable temperature of 40 degree C using thermometer

When temperature is reached, use the tweezers to remove one of the beetroot from its respective test tube and place it in the 40 degree Celsius heated water

 Let the root rest in water for exactly 1 minute which should be timed using stopwatch

 After 1 min time, use tweezers to remove the root from the heated solution and place it back into test tube of distilled water

 Set timer for 30 min; record time at which any color changes are noticed

Repeat these heating steps for the next 2 pieces of beetroot; increasing the temperature to 50 and 60 degrees Celsius.

Record all changes/differences/color onset within all 3 test tube samples

Rinse the 250 mL of heated water in the sink and refill beaker with 150 mL of distilled water

Heat water again to 40 degrees Celsius as determined by the thermometer

Place the first pea plant sample in the heated water – heat the pea plant for 15 min and then using the tweezers remove the pea plant and place back into petri dish

Remove the remaining heated water from the heating plate and put aside for data collection

Fill a new clean 250 mL beaker with distilled water and repeat this process exactly for the next two samples of pea plants raising the temperature to 50 and finally 60 degrees Celsius.

Record the physical appearance of each pea plant following heating; touch the plant and notice and changes in texture. Compare each samples color to the control sample’s color

Look at the samples of heated water from each pea plant sample and compare them

Discussion

The data collected during this experiment reveals the expected results discussed above.  When plants, experience abrupt/severe environment changes that alter cellular structure, cellular components are exposed.  In the beetroot’s case, the pigment contained within the deep vacuole of the cell drained into the surrounding water.  At a temperature of 40 degrees Celsius, only some pigment was exposed at first.  As heat increased further to 50 and 60 degree Celsius temperatures, the rate of leakage and volume of pigment dispersed into the water increased as well.  As illustrated in Fig. 1, temperature and pigment saturation maintained an inversely proportional relationship; increasing simultaneously.  The changes observed by the pea plants were less quantitative and more physically distinctive.  Each pea plant was overexposed to heat that permeated first the outer and then inner structural shell of the plant.  When the temperature reach 50 degrees Celsius it was evident that the cell membrane of the pea plant was no longer intact.  The peas inside the outer shell absorbed the surrounding water and wrinkled in order to accommodate the diffusion of water into the cell.  It was noticed for samples 2 and 3 that their petri dishes acquired water that had clearly been absorbed by the plant and then released during cooling.  Contributing once again to the “wrinkle” effect; swelling larger and then shrinking in the absence of heat.  The remaining water from the samples appeared foggy in color.  The inner cellular contents of the pea plant were dispersed into the surrounding water.

On a small scale, this experiment provides that in extreme external conditions, plant cellular functioning suffers.  Environmental incidences such as droughts, hurricanes, chemical leakages etc. are just some examples of stressors that inhibit the ability of plants to survive. Over time, adaptations can be made, but not in these extreme unexpected events.

Pea plants, along with many other vegetables are commonly canned for distribution and for preservation year round.  During the canning process, pea plants are heated to temperatures upwards of 200 degrees Fahrenheit in order to kill and microorganisms that may linger.  This canning process is the culprit behind the dull appearance and textural differences observed in canned foods.  Unfortunately, access to fresh vegetables all year round is not likely and can often be very pricey.

This experiment was relatively simple in order to avoid potential error and maintain consistent conditions that wouldn’t alter the results too greatly. Temperature increase/heating was the variable used in the experiment. Other experimental procedures may have investigated the cooling or freezing effect on these plants.  This would have served as a platform for more data collection, but with more potential for human error. The idea was to determine if extreme temperature change would prove destructive to the cell membrane of beetroots and pea plants.  Utilizing one extreme, I predict that any onset of extreme change in environmental temperature would negatively impact cellular membrane function resulting in pigment loss and vegetable denaturation. Fig. 2 shows the graphed results connected by a line.  This line position and direction shows expected results if more samples were tested at corresponding temperatures. The results in this graph account for the onset with which a change in water color was noticed.  As the temperature increases, the pigment change is noticed significantly earlier.  Determining the onset of color change in the pea plants was not an option.  The color change was not abrupt like that of the beetroot.  A pH indicator could be used with the pea plant part of this experiment to determine at which point the surrounding water changed due to movement of water in and out of the pea plant cells. The cytoplasm contained in plant cells contains water, salt, and even nutrients that are vital for cellular function.  If the process of diffusion, the concentration gradient would pull these substances out of the cell and into the surrounding water.  This would account for a change in pH level.

It might be interesting to see if prolonged (greater than 30 min) exposure to water (the control sample), would result in some eventual pigment saturation.  It could be argued that the process of diffusion would result based on the concentration gradient.

Some potential room for error could be possible during preparation of the samples. First, not all samples of beetroot will be the exact same size and shape. This might alter the rate at which water color changes or surface area exposed to heating.  During heating, the exact temperature recorded by the thermometer might change in the midst of administering each sample. Once water begins to heat and is exposed to a consistent heating source, the internal temperature will rise at a fast pace making it hard to sustain the same temperature.

The pea plant samples could have been larger. Using just one pea plant required a longer heating time in order to produce results.  If more pea plants were used temperature would be increased for each sample, but for less time.  The results from a larger sample would better confirm the results of the experiment.  Like the beetroot samples, the pea plants were not all the exact same size in length and width which could have accounted for different results.  In further investigation, heating all samples of the beetroot and pea plants at the exact same time under different temperature extremes would provide more data collection resulting in a more precise rate of membrane destruction in all cases.

Works Cited

Cooper, Geoffrey M. “Cell Membranes.” Cell Membranes. U.S. National Library of Medicine, 2000 Web. 30 Nov. 2015.

De, Deepesh N. “Plant Cell Vacuoles.” Google Books. CSIRO Publishing, 2000. Web. 30 Nov. 2015.

Torok, Zsolt. “Plasma Membranes as Heat Stress Sensors: From Lipid-controlled Molecular

Switches to Therapeutic Applications.” Plasma Membranes as Heat Stress Sensors: From Lipid-controlled Molecular Switches to Therapeutic Applications. Elsevier, June-July 2014. Web. 30 Nov. 2015.

Quinn, PJ. “Result Filters.” National Center for Biotechnology Information. U.S. National Library of Medicine, 1988. Web. 30 Nov. 2015.

White, Ian. “Re: Why an How Do Certain PH Ranges Affect the Beetroot Cell Membrane?” Re: Why an How Do Certain PH Ranges Affect the Beetroot Cell Membrane? MadSci Network, 25 Mar. 2004. Web. 30 Nov. 2015.