Thigmotropism Experiment

The Effects of Different Stress Levels on Bean Plants: Thigmotropism
May 3, 2012

Abstract Bean plants were planted and rubbed a certain amount of times a day to apply stress. This was to see how plants might survive in a windy area or in an environment where they might be constantly touched or moved around. They were put under four different stress levels, and the plants were measured before the start of treatment to determine how they were being affected. The hypothesis was that those who had the least amount of stress being applied to them would grow the tallest. They were measured and rubbed twice a week for two weeks and once on the third week. Results showed that the plants that were not touched grew the tallest, but those
that were touched ten times a day grew taller than those that were touched two or five times a day. It was concluded that the hypothesis was met only half way and measurements were not quite as expected, but they did not change drastically.
Introduction
Thigmotropism is a plant’s response and movement to physical contact (Thigmotropism).
In this experiment, we planted bean plants and put stress on them by rubbing them a certain amount of times a day. This was to see how they might survive in a windy area or in an environment where they might constantly be touched or moved around. The bean plants were under four different stress levels: the controlled plants were never touched, those that were touched two times a day, those that were touched five times a day, and those that were touched ten times a day. The plants were measured before the start of each treatment to determine how they were being affected. Our hypothesis for this experiment was that those who had the least amount of stress being applied to them would grow the
tallest.
Materials and Methods
In this experiment, we planted bean seeds in Miracle Grow potting soil and watered them daily until leaves were present. We made sure the plants received about the same amount of water each day to grow at a fairly close rate with one another. At that point, we were able to start the treatment. We had three sets of plants for each stress level, having a total of twelve plants. The controlled plants were never touched, the second set of plants were touched two times a day, third set of plants touched five times a day, and fourth set of plants touched ten times a day. Each rub equaled thirty seconds, therefore, those touched two times a day were touched for a total of one minute, those touched five times a day were touched for a total of two minutes and thirty seconds, and those touched ten times a day were touched for a total of five minutes. This provides somewhat large differences for the different levels of stress being applied. The plants were measured in centimeters from the soil to the top of the shoot system before each treatment. Measurements and rubbing occurred two times a week for two weeks and once for the third week.
Findings/Result
By the end of this experiment, the control plants, or those that were not touched, seemed to grow the tallest, but as shown in the table, the bean plants that were rubbed ten times a day seems to have grown taller than those rubbed two or five times a day.
All of the plants lived to the last day of treatment, but some were much healthier than others. The leaves seemed to have withered faster the more it was touched. From these results, it seems as though our hypothesis was only half correct. Although we predicted that the control plants would grow the tallest, we also thought those that were touched the most would grow the shortest. This was proven incorrectly because the bean plants that were rubbed ten times a day grew taller than those rubbed two or five times a
day.

Table: Measurements for Each Bean Plant
_____
4-10-12
4-12-12
4-17-12
4-19-12
4-23-12
T-0 (1)
17.5 cm
21.5 cm
83 cm
92 cm
136 cm
T-0 (2)
9 cm
12.5 cm
18.5 cm
22 cm
26.5 cm
T-0 (3)
17.5 cm
20 cm
30 cm
40 cm
98.5 cm
T-1 (1)
8 cm
9.5 cm
12.5 cm
14.5 cm
17.5 cm
T-1 (2)
11 cm
13 cm
14.5 cm
18 cm
17.5 cm
T-1 (3)
12.5 cm
14 cm
20 cm
20 cm
18.5 cm
T-2 (1)
13.5 cm
16 cm
16 cm
15 cm
18 cm
T-2 (2)
14 cm
17 cm
17 cm
21 cm
19 cm
T-2 (3)
16.5 cm
19.5 cm
18.5 cm
19 cm
18.5 cm
T-3 (1)
13 cm
14 cm
14 cm
15 cm
25 cm
T-3 (2)
12 cm
14 cm
15 cm
16 cm
17.5 cm
T-3 (3)
13 cm
15 cm
18 cm
18.5 cm
21.5 cm

* T-0 = Control plants (no rubbing)
* T-1= Rub 2X a day
* T-2= Rub 5X a day
* T-3= Rub 10X a day

Pictures

Conclusion/Summary After each day, the growth changes of each set of plants with different stress levels did not change drastically for the most part. A few plants jumped here and there and even shrunk by a centimeter or two, but on average, they seemed to grow at a fairly constant rate. From this experiment, it helped us understand the effects of Thigmotropism. By adding different stress levels on plants, their growth patterns get affected. This experiment showed that when there is physical contact with plants, they can get harmed, not grow properly, and eventually die faster than those that grow naturally. This conclusion may also vary because with this experiment, we cannot claim to say that the more it is touched, the less it will grow. This may also change if the plants were touched not only two times a week, but maybe everyday. This could alter the results, and it may show that our hypothesis was more accurate if more stress was added onto the bean plants.

Works Cited
"Thigmotropism A Plant 's Response to Touch!" Thigmotropism A Plant 's Response to Touch! Web. 02 May 2012.