Sample Lab Report on Photosynthesis and Plant Respiration

Biology classes often require students to write lab reports after conducting lab experiments. Students often struggle with writing a biology lab report as making one entails spending so much time on it when they are yet to finish their homework on other subjects. Lab reports, in general, require one to put in all the details that are vital in the whole process of the experiment. Thus, writing a lab report is exhausting as it is both time-consuming and brain-racking. However, writing a lab report need not be as complicated as it sounds. With that, here is a full sample of a biology lab report about photosynthesis and plant respiration which you can use to guide you in writing your biology lab report.

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Laboratory Report: Photosynthesis and Plant Respiration

Abstract

The process of photosynthesis is essential to plants as it is their way to produce a form of nourishment from sunlight, carbon dioxide, and water. Without photosynthesis, plants would not be able to produce oxygen which in turn would make it impossible for living and breathing beings to exist. This biological experiment will use four plants from the same species, specifically Cestrum nocturnum to demonstrate just how important exposure to direct sunlight and sources of moisture and carbon dioxide is essential to the process of photosynthesis. The four plants exposed to varied conditions displayed different results.

Objectives

1. to determine the basic features and importance of photosynthesis;
2. to demonstrate the photosynthetic activities of plants; and
3. to determine the role of sunlight in photosynthesis

Introduction

Life on earth would cease to exist without the sun. The solar energy the sun produces is crucial to the survival of living organisms on the planet. Plants and other photosynthetic organisms have chloroplasts. Chloroplasts are cellular organelles that capture the solar energy from the sun and convert it to chemical energy which is then stored in sugar and other organic molecules. This process of conversion is called photosynthesis.

On an ecological scale, photosynthesis is responsible for nourishing almost all life forms whether directly or indirectly. An organism acquires the organic compounds needed for its energy by being an autotrophic organism or consuming photosynthetic organisms for heterotrophic organisms. Autotrophs can supply their own food and can sustain themselves without consuming anything derived from another organism.

Autotrophs are able to produce their own organic molecules from carbon dioxide and other inorganic raw materials found in the environment. They are the ultimate sources of organic compounds for all non-autotrophic organisms. Consequently, heterotrophs are unable to produce their own food and they have to feed on compounds or substances produced by other organisms. Heterotrophs gain biological compounds by consuming photosynthetic organisms or autotrophs.

Almost all plants are autotrophs for they only require water, carbon dioxide, and soil nutrients. Specifically, plants are photoautotrophs, which means they are organisms that use light as a source of energy to make their own food. However, plants are not the only autotrophic organisms. These also include algae, euglena, and Cyanobacteria and Anoxygenic Photosynthetic Bacteria.

Chloroplasts are present in all green parts of the plant (leaves, stems, unripe fruits, etc.) but are found mainly in the mesophyll, the tissue in the interior of the leaves, which is the major site of photosynthesis for most plants.

Carbon dioxide enters the leaves through microscopic pores called stomata where oxygen also exits. Water is absorbed by the roots and is delivered to the leaves through veins. Leaves also use veins to export sugar to roots and other non-photosynthetic parts of the plant. Chlorophyll, which gives leaves their green pigment, can be found in the chloroplast. The light energy absorbed by chlorophyll kickstarts the production of organic molecules in the chloroplast. 

The green parts of the plants produce organic compounds and oxygen from carbon dioxide and water in the presence of light. We can summarize the complex series of chemical reactions in photosynthesis with this simple chemical equation: 

Photosynthesis has two major stages: light reactions and dark reactions. Light reaction or light-dependent process occurs in the chloroplasts where chlorophyll electrons are excited to a higher energy state once the light strikes the leaf. The energy is stored by forming a chemical called ATP (adenosine triphosphate), a chemical compound that is made up of the nucleotide adenine - ribose sugar bond very similar to the building blocks of human DNA.

The stored energy is used in the second process. Water is chemically broken down in the process, releasing oxygen as a byproduct. The second stage is known as the dark reaction or light-independent process where it takes place in the chloroplasts. In this stage, the products of the light-dependent process are used to form carbohydrates. Carbon dioxide from the air is ‘trapped’ and ‘modified’ by hydrogen molecules to form carbohydrates. The chain of reactions in the light-independent process is known as Calvin cycle.

Conditions and Materials

• Access to direct sunlight
• Well-lit room
• Shaded area
• Small clear plastic bag
• Clear adhesive tape
• 4 potted plants of the same species (Suggestion: Night-blooming Jasmine plant ( Cestrum nocturnum) or any other plants with green leaves)
• Camera or any image capturing device 

Procedure

1. Line the potted plants in one area and make sure that each plant is well soiled, fresh, and healthy.
2. Label one plant as "PLANT A", then place it inside a well-lit room in your house. Make sure that it is well-lit throughout the experiment.
3. Label the second plant as "PLANT B" then put it in a dark room or in a shaded area. Make sure that the plant remains in the dark throughout the experiment.
4. Label the third plant as "PLANT C", then position it outside where it can receive direct sunlight.
5. Label the fourth plant as "PLANT D", then place it beside Plant C so that it is exposed to sunlight, too. But, cover some of the leaves with small pieces of clear plastic bags. Seal the plastic bags by taping it around the opening to prevent the plastic from falling off. Make sure that the leaves remain completely covered throughout the experiment.
6. Leave the plants for three days and make sure they remain in their proper places. Water all of them accordingly.
7. Observe the plants once every twelve hours. Take pictures of each plant and note your observations, especially the changes on their appearances such as the color of the stems and leaves (take note of their blooms, too, if you used a flowering plant).
8. At the end of the third day, gently remove the plastic covers of Plant D.
9. Take a photo of each plant and note the differences.

Results and Discussion

Table for results, observations, and interpretations of the performed experiment.

Guide Questions

1. Why are photosynthesis and cellular respiration complementary processes?
     Photosynthesis and cellular respiration are complementary processes because the required substances produced by the other are obtained by the other. They both consume and produce the same substances but in different manners. Plants consume the carbon dioxide they need through these processes while other living organisms get the oxygen they need from autotrophic organisms like plants. This means that both processes are necessary for the energy exchange upon which living organisms thrive upon. Photosynthesis and cellular respiration are complementary because the process of photosynthesis requires energy which cellular respiration releases and photosynthesis produces food which the process of cellular respiration breaks down.
2. Why do the leaves exposed to sunlight appear dark? What organelle is responsible for this?
     The leaves exposed to sunlight may have most chloroplasts found in the upper layer of the leaf making it dark. The concentration of chloroplast and the difference in the number of various pigments in a leaf are some of which cause the dark pigmentation of the leaf.
    There are many different pigments but chlorophyll is the only one that can help plants absorb the energy needed to build tissues. Chlorophyll is found in chloroplasts. Chloroplast is the organelle mainly responsible for the color seen in plants and is also responsible for the photosynthesis of plants.
3. What color of light is least efficient in driving photosynthesis? Why?
     Green, because green light is mostly transmitted or reflected by the plants instead of being absorbed by the photosynthetic pigments. On the contrary, red light is the most effective in photosynthesis as plants effectively convert red light into energy.
4. How do carbon dioxide molecules used in photosynthesis reach and enter the chloroplasts inside the leaves?
     Carbon dioxide molecules enter the leaves through the stomata present on the leaves.
5. Explain how all life depends on photosynthesis.
     Organisms undergoing photosynthesis can provide food in the form of sugars or carbohydrates to all other living organisms. This can happen directly or indirectly by harnessing the power of the sun to build these carbohydrates, a feature that non-photosynthetic organisms can not do. Additionally, photosynthetic organisms also produce oxygen, a substance required by all aerobically-respiring organisms.

Conclusion

Plants are autotrophic organisms which means that they provide their own food and they do photosynthesis to obtain energy. Observing the shaded plant compared to the non-shaded plant, it shows that the sunlight captured by the exposed plant results in more compact growth and more flower bud formation while the shaded plant barely bloomed, and some parts of the leaves turned yellow to brown. Other than sunlight, plants also need carbon dioxide and moisture to produce their own energy. Without sunlight, carbon dioxide, and water, plants cannot thrive. They provide major roles in the plants’ photosynthesis and should be properly supplied to the plants in order for the plants to grow fully.

Glossary

• Autotrophic organism – Autotrophic organisms are organisms capable of producing their own sustenance through photosynthesis. Examples of autotrophic organisms are plants algae, euglena, and Cyanobacteria and Anoxygenic Photosynthetic Bacteria.
• Cellular respiration – Cellular respiration is the process wherein oxygen and other nutrients (e.g. solar energy from the sun) and discards carbon dioxide and water.
• Chlorophyll – Chlorophyll is the green pigment found in plants and other autotrophic organisms.
• Chloroplast –  Chloroplast is the site where photosynthesis happens. It is the one responsible for capturing sunlight and storing the energy from it at the same time while releasing oxygen and water.
• Heterotrophic organism –  Heterotrophic organisms are organisms incapable of producing their own food and therefore rely on other organisms like plants and animals to get the nutrients they need.
• Mesophyll – Mesophyll contains chloroplasts where photosynthesis happens and is found in the inner tissue of a leaf of a plant.
• Photosynthesis – Photosynthesis is the process used by autotrophic organisms to produce their sustenance by converting light energy into chemical energy through cellular respiration.
• Stomata –  Stomata is found in the epidermis of plants and is the one responsible for controlling the carbon dioxide and oxygen exchange.

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Reference

Bailey, R. (2019, May 8). Organisms That Use Photosynthesis. ThoughtCo. https://www.thoughtco.com/all-about-photosynthetic-organisms-4038227

Note on the reference: Most lab reports, especially high school science experiments, do not require the students to utilize a reference page. However, always ask your teacher if you need to cite your sources to avoid plagiarism problems.