Lab Report: The Effect of Light Intensity on Plant Growth
Objective: To investigate how varying light intensities affect the growth of plants.
Hypothesis: If plants are exposed to higher light intensities, then they will grow taller and have
more biomass, as light is a key factor in photosynthesis.
Materials:
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4 potted plants (same species, same age)
4 different light sources (e.g., 25%, 50%, 75%, and 100% of natural light intensity)
Measuring ruler
Weighing scale
Timer or stopwatch
Soil
Watering can
Notebook for recording data
Methods:
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Select four plants of the same species and ensure they are of the same age and size.
Place each plant in a separate area where light intensity can be controlled.
Assign different light intensities to each plant: 25%, 50%, 75%, and 100% of natural light.
Expose each plant to the assigned light intensity for 12 hours daily over a period of 3
weeks.
Water each plant equally and maintain all other conditions (temperature, soil, etc.) the
same for all plants.
Measure the height of each plant every week and record the data.
At the end of the experiment, measure the final height and weigh each plant to
determine biomass.
Analyze the data to determine if light intensity has a significant effect on plant growth.
Results: The following data were collected during the experiment:
Light Intensity
Week 1 Height
(cm)
Week 2 Height
(cm)
Week 3 Height
(cm)
Final Biomass
(g)
25%
4
7
9
10
50%
5
9
12
15
75%
6
11
16
20
100%
7
13
20
25
Analysis: From the data, it is clear that plants exposed to higher light intensities grew taller and
had greater biomass. The plant under 100% light intensity had the most growth, both in height
and biomass, while the plant under 25% light intensity showed the least growth.
Conclusion: The results support the hypothesis that higher light intensities promote better
growth in plants. Plants exposed to 100% light intensity grew the most, suggesting that light is a
critical factor in the photosynthesis process that contributes to plant growth. This experiment
emphasizes the importance of light in plant development, especially in controlled agricultural
environments.
Discussion: While the results support the hypothesis, other factors such as temperature, soil
quality, and plant species could have influenced the results. Future experiments could explore
the effect of light duration or other environmental factors like temperature and humidity on plant
growth. Additionally, different species of plants might react differently to varying light intensities,
which could be another avenue for further research.