How do different levels of light affect the rate of seed germination in radishes?

1. Running head: BIOLOGY 1
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How do different levels of light affect the rate of seed germination in radishes?

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Abstract
The aim of this study was to determine how different levels of light affect the rate of seed
germination in radishes (Raphanus sativus). Light is a necessary condition in the germinating
plant that is necessary for occurrence of photosynthesis. Deeply buried seedlings die if not
exposed to light. The available food supply is exploited and more is needed to support growth.
Availability of the element is not a requisite but plays an important role in some plant species.
Some seeds require light while others need darkness. However, some are not affected by any of
the conditions. The above aspects are necessary for the imbibition of water, increase in metabolic
activity and swelling of cells. It leads to germination. Six seeds were mixed in soil and water in a
petri dish. The apparatus were organized in three groups exposed to different lighting conditions.
One labeled arrangement was exposed to maximum, partial and zero sunlight. Same measures of
the variables were used across all the setups. The observations after three days showed that the
seeds in darkness germinated as well as those kept in much sunlight. It falsified the alternative
and justified the null hypotheses.

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Table of Contents
Abstract 2.......................................................................................................
Table of Contents 3............................................................................................
Personal Statement 4..........................................................................................
Design 4..........................................................................................................
Aim 4..........................................................................................................
Research question 4.........................................................................................
Introduction 4................................................................................................
Hypotheses 6.................................................................................................
Variables 6....................................................................................................
Method 8.........................................................................................................
Apparatus and materials 8.................................................................................
Safety requirements 9......................................................................................
Procedure 9...................................................................................................
Data Collection and Processing 12...........................................................................
Qualitative 12................................................................................................
Quantitative data 12........................................................................................
Conclusion 14...................................................................................................
Discussion 14....................................................................................................
Evaluation 15.................................................................................................
Improvements 15............................................................................................

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Personal Statement
A study on the effect of light on germination of the radish seeds is important to my
prospects of growing the plant in my garden and farm. In return, my interest in gardening drove
me to investigate how different levels of light affect the rate of seed germination in radishes.
Design
Aim
The aim of this study is to determine how different levels of light affect the rate of seed
germination in radishes.
Research question
How do different levels of light affect the rate of seed germination in radishes?
Introduction
Germination is the process by which a seed embryo begins growing. The process begins
when the embryonic root bursts through the seed coat. Most plants begin developing through the
natural procedure. Some seeds germinate immediately whereas others have to stay for a
dormancy period. However, all varieties only resume growth when a set of conditions are
available to permit the process.
References 16...................................................................................................

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The waiting time in some plants’ seeds is meant to fulfill some prerequisites. For
instance, temperature and mechanical processes affect the duration taken by certain plant species
to germinate. Other aspects in play include the incomplete seed development, an impervious seed
oat, presence of regulators of growth and a need for pre-chilling.
Generally, all varieties of seeds require favorable environmental conditions for successful
germination. The most critical provisions are the optimal temperature, moisture, air and
appropriate light levels. However, the specific amount of the above variables differs for each
plant type. Optimal temperatures neutralize the effect of chemicals that inhibit growth in the
embryo. Appropriate warmth levels permit the metabolic processes that support growth. It may
vary among species and the environmental conditions.
Water is an essential component that causes the expansion of the embryo as well as the
softening of the encasing coat. Furthermore, more moisture is required in the vigorous
metabolism of the plant during germination. Besides, it is important for removal of inhibitors of
the process.
Light is a necessary condition in the germinating plant for the occurrence of
photosynthesis. Deeply buried seedlings die if not exposed to light. The available food supply is
exploited and more is needed to support growth. Availability of the element is not a requisite but
plays an important role in some plant species. Some seeds require light while others need
darkness. However, some are not affected by any of the conditions. The above aspects are
necessary for the imbibition of water, increase in metabolic activity and swelling of cells. It leads

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to germination. Phytochrome is a photoreceptor pigment in light-sensitive seeds’ coats. It
communicates with the seed to trigger or stop germinating in response to the environment.
Radish (Raphanus spp.) is a cool season vegetable plant that grows easily when the
conditions are favorable. Although native to China, it can grow in the hardiness zones in some
parts of the US. The crop thrives well when planted outdoors with maximum exposure to
sunlight of six to eight hours per day. Radish seeds germinate properly under temperature
conditions of 55 to 75 degrees Fahrenheit. It takes 3-4 days under the ideal circumstances for the
seeds to fully germinate. However, it may never sprout or take longer if it’s planted deeper or in
cool soils. A minimum of 6 hours exposure to light is necessary for the performance of the crop.
Hypotheses
Null hypothesis (H0): The different levels of light do not affect the rate of germination. No
notable differences in growth of radish seedlings in varied lighting conditions.
Alternative hypothesis (H1): The germination of seeds exposed to 1005 of light is at a higher rate
than the ones in limited exposure. Radish seeds will need sunlight top germinate since the crop
requires light to grow. Some seeds will germinate in the lit samples as well as the dark ones. In
the experiment, most of the seeds exposed to direct sunlight will germinate compared to the ones
in darkness or under shade.
Variables
The independent variable

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Hours of exposure to direct sunlight- the determinant factor is the level of light. Seeds of radish
will be exposed to different hours of direct sunlight. For instance, the sets will be 7 hours, 3
hours and zero hours.
Dependent variable
The rate of germination in the experiment will be measured by the number of radish seedlings
that will germinate under different sunlight conditions.
Controlled variables
Variable How Reason
Temperature The samples were kept in a
room that as maintained at
25°C.
The procedure was essential
to remove the environmental
factor that would cause
differential warmth in the soil.
Water volume The volume of water used to
moist the soil was determined
by the measuring cylinder
instead of a beaker
Having the same level of
moisture in all set-ups was
important to rule out its
moderating effect
Mass of soil used The quantity of soil in which
the seeds were planted was
determined by the weighing
machine.
The mass of the soil upon
which the seeds are planted is
regulated to avoid differences
in depth of exposure.

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Method
Apparatus and materials
➢ 12 petri dishes
➢ 72 radish seeds
➢ 12 sandwich bags
Humidity The same room was used for
the experiment all the time
The step was necessary to
manage the variation in
humidity that can affect the
rate of germination
Plant species One variety of Radish plant
seeds were used, Raphanus
sativus
To keep the seed
characteristics similar so that
no variety will have
extraneous rates over others
Setup used The same setup was used
throughout the experiment for
all variables
To reduce the variation in
results due to inaccuracies and
invalidities of the process

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➢ 60 ml of distilled water
➢ 24 filters
➢ 1x Marker pen
➢ 1x Measuring cylinder
➢ 1x Beaker
➢ Lump of soil
➢ 1x Thermometer calibrated in degrees Celsius
Safety requirements
The hand gloves and a lab coat were used to protect one from being dusted or dirtied with soil
and mud.
Procedure
➢ Collect all the materials and apparatus stipulated above
➢ Divide 12 petri dishes into groups of four. Label them according to the following
categories;
I. 4 Labeled 7 hour exposure
II. 4 Labeled 3 hour exposure
III. 4 Labelled darkness/ zero exposure
➢ Place one filter on the bottom of each petri dish

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➢ Spread uniformly six seeds of the Radish plant on the filter in each petri dish
➢ Using the measuring cylinder, measure 5ml of distilled water and pour on the seeds
➢ Using the weighing machine, weigh 10g of soil from the lump and spread on top of the
Radish seeds
➢ Place a covering filter on top of each petri dish
➢ Cover the apparatus with a lid
➢ Keep a complete set of the petri dish into a sandwich and put in a bag
➢ Label three boxes with; 7 hour exposure, three hour exposure and darkness
➢ Place all the categories of petri dishes into differently labeled boxes
➢ Place the boxes in a darkened room.
➢ Every day take the 7-hour labeled petri dishes to a field under direct sunlight direct
sunlight from 7 am to 2.pm, the 3-hour labeled ones from 7am to 10am. Keep the dishes
labeled dark or zero hours in the dark room drawer for the 4 days of the experiment.
➢ Remove the exposed petri dishes keeping them in their respective boxes after the time
expires.
➢ Check the petri dishes from the second to the fourth day to see if the seeds have
germinated.
Control: the radish seeds kept in the total darkness

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Replication of the experiment: The four radish seed petri dishes exposed to longer duration of
sunlight, lesser time and in dark without light.
Figure 1-7: The petri dishes set up
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Planted set up after the 3rd day
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Petri kept in darkness 7 hour exposure setup 3-Hour exposure set-up

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Data Collection and Processing
Qualitative
The seeds began germinating from the second to the third day. The entire apparatus was observed
and seedlings emerged from the petri dishes. However, the ones exposed to the sunlight
germinated the first.
Quantitative data
The raw data of the number of seedlings that germinated in each category of sunlight exposure
are shown in the following table. Figure 8
Duration of exposure to
light
Number of seeds that
germinated
Average rate of
germination
Percentage rate of
germination
No light/ darkness 21 5.3 88%
3-hour direct sunlight 19 4.8 80%
7-hour direct sunlight 22 5.5 92%

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Figure 9: Below is the chart showing the average rate of germination at different levels of
sunlight exposure.
!
Seed germination rate
4.6
4.8
5.1
5.3
5.5
No sunlight/darkness 3-Hour Exposure 7-Hour Exposure
Seed germination rate

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The observed rates indicated that the rate of germination of the radish seeds for the petri dishes
exposed to longer sunlight hours was the same as that kept entirely in darkness. However, the
time taken for the seedlings to sprout was shorter for the ones placed in light.
Conclusion
The study findings falsified the alternative hypothesis. It confirmed that there is no
difference in the rate of germination of seeds kept in the light for a long duration and the ones in
darkness. Varying levels of sunlight does not affect the process. The percentage rate of growth
was 92%, 80% and 88% for seeds exposed to sunlight for 7 hours, 3 hours and zero hours
respectively. Out of the 24 seeds exposed to light for the maximum duration, 22 of them
germinated. On the other hand, 21 seeds out of 24 placed in sunlight for 3 hours sprout up.
Finally, the ones kept in darkness had 88% germination rate.
Discussion
The results observed in the experiment surprised the foundation of our understanding.
Although light is essential for the growth of the radish plant, it is not necessary for the
germination. Both the seeds kept in maximum sunlight as well as those placed in total darkness
germinated at the same rates. On the other hand, the difference was significant for the seeds that
were exposed to shorter hours of sunlight. Generally, the variations in the three apparatus were
minimal.
The experiment indicates that the seeds did not need the sunlight for sprouting. Radish
seeds can germinate well in darkened gardens inside the house. Such findings are important to

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the farmers of the crop. Gardeners can also realize that the crop can be planted deep in the soil. It
will perform well because it does not need the sun to begin the growth process.
A significant observation on the effect of light was on the strength of the seedlings’
stems. The seeds exposed to the sunlight had straight stems whereas the ones in darkness were
feeble with coiling shoots. It indicates the importance of sunlight at the growing stage after
germination.
Evaluation
The study findings agree with the existing works of Rillero (2010) that light has no effect
on germination of radish seeds (Ravanus sativus). Kolodziejel (2015) supported the facts holding
from his experiment that the species germinates in light as well as dark conditions. Bewley
(2012) justifies the phenomena stating that the plant variety is insensitive to the effect of lighting
during germination (Bewley, 2012).
Although the results of the study mirror the findings of existing literature, some aspects
that could have affected the observed outcomes are analyzed. A variable like outside temperature
was not controlled when the samples were exposed to the sunlight. It could have contributed to
the death of the seeds. Secondly, the salinity of the soil was not determined and its consequences
were ignored. Thirdly, the mass of the seeds was not measured.
Improvements
To improve the findings next time, the experiment will be carried out in a room and the source of
light will be a glowing lamp. It has minimal heat in the light it emits. Therefore, it will eliminate
the chances of death of seeds due to the heating effect of the sunlight. Secondly, the salinity of

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the soil will be determined so that a neutral lump is used. Thirdly, the mass of the seeds used will
be obtained to ensure that a standard measure applies for all seedlings. Further studies will also
seek to determine the impact of differences in the weight of the radish seed in intervening
germination.
References
Bewley, J. (2012). Seeds: Physiology of Development and Germination. New York: Springer.

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