Title: Germination in Plants – Sensitivity and Coordination in Plants – Growth Movements.

Aim: To investigate tropic movements in germinating seeds of red bean under dark and light
conditions.

Apparatus Material

2 three quarters-cut 2L clear bottles Paper Towels

Plastic/Cling wrap 20 Red Beans

Spray Bottle

Rubber Bands

Ruler

String

Method:
1. 20 unrefrigerated red beans of the same size and age were obtained.
2. 2 2L soft drink bottles were cut three-quarters way up and washed. The bottles were then
lined with 6 layers of tissue paper and carefully moistened using the spray bottle, so that
it clings to the side of the bottle.
3. The seeds were distributed around the bottles, being placed midway down in between the
moistened tissue and the sides of the bottles. Each seedling was positioned differently,
some upright, others sideways, and others upside down.

4. Using the rubber bands provided, a sheet of clear, perforated plastic was secured over the
mouth of both bottles. A knife was used to perforate the plastic wrap so as to allow air
into the bottles.
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5. The tissue paper was always kept moist.
6. One bottle containing the seedlings was kept in a cool, dark place whereas the other bottle
was kept in a well-lit location.
7. The seeds were allowed to germinate for 5 days until the radicle and plumule were visible
in each and then allowed to grow for 10 days afterwards.
8. On each of the 10 days at the same time of day, 5 seedlings from each bottle were
examined through the bottle. The same 5 seedlings were examined and measured each
day.
9. Using a string and a ruler, the lengths of the roots and shoots of the 5 seedlings from each
bottle were measured daily, ensuring that the position of the seedlings were unchanged.
10. All measurements were recorded in 4 suitable tables for plumule length and radical
length, respectively, with room left for the average values in all.
11. At the end of the 10 days, a large, fully-labelled and annotated drawing of ONE of the 5
seedlings from each bottle was made, taking into consideration the position of the
seedling.
12. The roots and the shoots were labelled clearly and comparisons of the direction of their
growth in the annotations were made.
13. Using the average lengths per day for the 10-day period, a line graph was created to
compare the lengths of the plumule for the seedlings grown in the light vs. those of the
seedlings grown in the dark. Days were labelled on the x-axis and avg. length of
plumule/cm on the y-axis.

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Results:
TABLE 1 SHOWING THE SHOOT (PLUMULE) LENGTHS OF THE 5 SEEDLIGS
GROWN IN A WELL-LIT LOCATION OVER A 10 DAY PERIOD.

Shoot Shoot

Day Length Of Shoot of Average

Each Seed, CM Length, CM

1 2 3 4 5
1 10 5 2 4 1 4.4
2 10.5 6 2 5 1 4.9
3 17 10 1.5 10 8 9.3
4 20 12 1.5 14 13 12.1
5 24 20 1.5 18 18 16.3
6 29 27 1.5 19 20 19.3
7 30 31 1.5 19 24 21.1
8 36 34 1 20 28 23.8
9 37 34 0.5 20 32 24.7
10 39 36 0 21 33 25.8

TABLE 2 SHOWING THE ROOT (RADICLE) LENGTHS OF THE 5 SEEDLIGS

GROWN IN A WELL-LIT LOCATION OVER A 10 DAY PERIOD

Root Root

Day Length of Longest Root of Average

Each Seed, CM Length, CM
1 2 3 4 5
1 5 3 0 4 2 5
2 7 4 0 4 5 6.4
3 9 6 1 5 6 7
4 12 6 1 7 6 6.2
5 14 8 1 9 6 7.5
6 14 10 1.5 9 7 7.5
7 14 10 2 9 9 7.5
8 14.5 11 3 9 10 7.6
9 14.5 11 3 9.5 13 7.8
10 15 11. 3 10 13 8.2

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 5

TABLE 3 SHOWING THE SHOOT (PLUMULE) LENGTHS OF THE 5 SEEDLIGS

GROWN IN A DARK, COOL LOCATION OVER A 10 DAY PERIOD.

Shoot Shoot

Day Length Of Shoot of Each Average Length,

Seed, CM CM

1 2 3 4 5
1 0 8 2 6 8 4.8
2 0 13 5 11 12 8.2
3 0 18 8 17 14 11.4
4 0 24 9 23 18 14.8
5 0 26 13 24 24 17.4
6 0 27 19 26 29 20.2
7 0 29 22 29 34 22.8
8 0 30 24 31 36 24.2
9 0 30 25 35 38 25.6
10 0 30 25 37 39 26.2

TABLE 4 SHOWING THE ROOT (RADICLE) LENGTHS OF THE 5 SEEDLIGS

GROWN IN A DARK, COOL LOCATION OVER A 10 DAY PERIOD.

Root Root

Day Length of Longest Root of Average Length,

Each Seed, CM CM
1 2 3 4 5
1 0 3 1 1 5 2
2 0 5 3 1 5 2.8
3 0 6 3 2 10 4.2
4 0 9 6 4 10 5.8
5 0 10 6 4 10 6
6 0 10 6.5 2 9 5.5
7 0 13 7 2 6 5.6
8 0 13 8 1 6 5.6
9 0 13 8 0 4 5

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 10 0 13 8 0 3.5 4.9
Introduction:
- Plant movements, known as tropisms or growth movements, are essential for plant
development and survival. These movements are primarily controlled by a hormone
called auxin, produced in the tips of roots and shoots, which are the plant's growing parts.
Auxin diffuses to regions just behind the tip, where it promotes growth. Factors such as
light and gravity influence plant growth by affecting the concentration and location of
auxins.

- There are two main types of tropisms. The first, phototropism, is growth in response to
light or sunlight. The second, geotropism, is growth in response to gravity. These
movements are crucial as they affect the plant's growth, size, shape, nutrition, and auxin
content, ultimately influencing the plant's ability to survive. Phototropism ensures that
plants maximize their exposure to light, essential for photosynthesis, while geotropism
ensures that roots grow downwards for anchorage and nutrient absorption, and shoots
grow upwards to access light.
Discussion:
- The tissue paper was moistened to help the red bean seeds stick to the container and stay
in a fixed position during the experiment. Additionally, during germination, seeds require
water. The moistened tissue provided the necessary water for the activation of digestive
enzymes, known as hydrolytic enzymes, which break down the food storage in the seeds
to nourish the embryo of the red beans.

Observation of Red Beans grown in a well-lit area.

- Initially, the radicles (roots) of the red bean seedlings appeared cream-colored and had no
leaves. In contrast, the plumules (shoots) were green and leafy. This is because the beans
in a well-lit area had access to sunlight, enabling them to produce chlorophyll, which
gave the leaves their green color and a broader, healthier appearance. The stems were
also thicker than those of seedlings kept in a dark, cool place, as they could access
sunlight and undergo photosynthesis.

- The plumule grew upwards due to phototropism, where auxins accumulated on the
shaded side of the plumule, promoting growth towards the light. Meanwhile, the radicle
grew downwards because auxins in the roots slow down growth. Unlike the shoot, where
auxins gather on the lower side due to gravity, in the root, the upper side grows faster as
it is less affected by auxins, causing the radicle to grow downward.

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 Observation of Red Beans grown in a cool dark area.
- The seedlings grown in the dark were noted to be very thin, long, and tall, with a yellow
color instead of green. This yellowing was due to the lack of sunlight, which prevented
the production of chlorophyll. Without sunlight, the seedlings couldn't photosynthesize to
produce food, leading to the depletion of their food stores and resulting in smaller roots
and shoots.

- In the dark, the seedlings underwent a process called etiolation. In this process, the auxins
produced in the growing tips diffused down the stems, causing the cells to elongate
rapidly in search of sunlight. This led to weak, elongated stems and the pale-yellow color,
known as chlorosis. This trend can be seen in the graph as the seeds grown in the dark
had a more exponential growth at the beginning than the ones in the well-lit area. This is
because the plant urgently needs sunlight.

Precautions:
1. The seeds were kept in a stable environment with minimal temperature fluctuations
2. Ensure that there were enough holes in the plastic bottles to allow oxygen to enter
3. Check that enough paper towels were used to ensure red beans stuck to the bottle and
didn’t move during the experiment

Limitations:
1. The seedlings were not watered efficiently which resulted in them drying up and the
experiment needing to be repeated.
2. The red beans used were not all the same size resulting in varying results.
3. A small sample size was used which may not provide accurate results

Sources of error:
1. Seeds received varying amounts of water, leading to inaccurate results
2. Some beans may have been spoiled or rotten before experiment causing seedlings to not
sprout
3. The paper towels for the red beans in the cool dark place was not always moist which
may have interfered with growth of beans

Improvements:
1. Use a larger sample size for a wider set of results

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 2. Inspect the set of red beans prior to experiment and replace any rotten or spoilt ones.
3. Soak the red beans overnight before experiment for a faster germination process.

Conclusion:
- Despite the limitations of experimental error, geotropic and phototropic growth
movements were observed in the red beans grown in dark and well-lit areas. The beans
grown in the dark showed geotropism and etiolation due to the absence of sunlight, while
the beans grown in the light displayed phototropism, allowing them to photosynthesize
and develop normally.