Research Background (Classroom
Heat Shock Experiment)
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.
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.
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 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.