Research Background (Classroom Heat Shock Experiment)

  • Procedure:

         We began our heat shock experiment on January 31, 1998. The students planted three pots of cotton, sunflowers, radishes, and cucumber plants. Each pot contained 10 seeds assuring at least some growth in each pot. The plants were then allowed to germinate in a dark cabinet for 7 days. When the plants were brought out in the open the stems were ivory white and the cotyledons were yellow. The cotton seeds never germinated at all. It is believed that at night our school building heat was turned down too low to meet the soil temperature requirements for cotton germination. The students chose which plants from each group would be the control group, the heat shock group, and the challenge group. The control group was put under a plant light to grow naturally. The heat shock group was placed in an oven, which was placed at the lowest setting 57-590C for four hours.

  • Data:

         The students observed that within two days of the experiment the control group was greening up nicely. The heat shock group showed some signs of distress with 20% of the sprouts dead and another 30% showing lacking photosynthetic qualities. This was noted by observing cotyledons remaining yellow and spotting. The other 50% showed signs of recovery by greening up when placed under the plant light. The challenge group was completely destroyed, partly because of the inability to lower the temperature below 570C.

         By the end of the second week, the control group continued to grow normally. The sunflowers averaged 1.2 inches of growth per stem, the radishes averaged 0.8 inches per stem, and the cucumber plant began to show signs of vine characteristics with an average of 1 inch per stem. The heat shock group showed growth signs but considerably slower than that of the control group. The sunflowers averaged only 0.5 inches of growth, the radishes averaged 0.6 per stem, and the cucumber plant averaged 0.5 inches of growth. The challenge group was not considered from this time on because of death of the plants.

         By the end of the 6th week, the control group continued to stay ahead of the pack. The sunflowers were measured and averaged at 18 inches per stem. The radishes only grew an average of another inch but the leaf sizes increased considerably. There were also signs of actual radish vegetables visible. The cucumbers were beginning to flower with 12 visible and the vines had averaged a growth of 21 inches in length. The heat shock group seemed to recover but was noticeably stunted in growth, leaf production and coloration, and flower production. The sunflowers averaged only 12 inches per stem. The radish stems were similar to the control group but noticeably thinner in that not as many stems survived. Only 47% of the stems survived. The radish vegetables that appeared were slightly deformed. They were more oblong in shape than round like the control group. The cucumber only had 1 vine that reached a length of 13 inches. It also only displayed 4 visible flowers.

  • Results:

         The students observed noticeable differences between the control group and the heat shock group immediately after the heat shock group was exposed. They learned that the plants that were heat shocked stayed behind in growth and reproduction throughout the experiment. The plants did survive the early exposure to high temperature but the growth was definitely affected. We are now in the process of allowing the plants to continue to grow to the point that the cucumbers produce fruit and the sunflowers flower to observe the productivity effects. The students have already noticed a difference in the radishes.

  • Conclusion:

         The students concluded that even short exposures to extremes in heat had a damaging effect on plants. They were able to see the importance of isolating the protective proteins in plants and genetically engineering plants to handle the stress better. The plants found in our area of Texas such as cotton, corn, what, soybean, and peanuts would all benefit greatly from this study. Among the many extreme conditions we face here in west Texas, intense heat and low moisture levels are always a danger to our crops.