Early Experiments On Photosynthesis: Experiments And Factors Affecting

What Is Photosynthesis?

Photosynthesis is a process in which green plants, algae, and certain bacteria convert light energy into chemical energy and subsequently produce glucose and oxygen from carbon dioxide and water. The process, therefore, forms the basics of how energy flows through the food chain, for it forms the primary energy source for almost all life forms on Earth.

Early experiments by Joseph Priestley and Jan Ingenhousz in the 18th developed the fact that plants could be able to produce oxygen and that the process had to be completed under the presence of light. To this extent, studies of such nature laid the foundation for our understanding of photosynthesis. The ancient theories evidenced that photosynthesis was propped to play the most essential function in maintaining life on Earth and enabling the proper functioning of its ecosystems.

Ancient Theories Of Plant Growth

The ancient theories related to plant growth are:

Aristotle’s Theory

Aristotle was a Greek philosopher who theorized that plants grow out of the soil and also have some form of a soul that allows them to emerge and procreate. He showed his concepts of plants as passive animals that only absorb nourishment from the soil, where they have no idea about sunlight or other essentials' impact on them.

Theophrastus’ Observations

Theophrastus, Aristotle's student, vented much-entering botany by systematically monitoring the growth of plants. He noted several functions of plants, primarily on how different plants react to their surroundings. Still, it appears he didn't identify the role that sunlight played in photosynthesis. His contribution laid the building blocks for future botanical research and also led to the fact that empirical observations play a significant role in plant biology.

Van Helmont’s Experiment (1648)

Van Helmont decided to run an experiment on the measurement of plants' growth by water. He took a single willow tree, planted it in a pot, and weighed it, including both the tree and pot, with a known soil weight. Then, throughout five years, he added water to the pot but not additional soil.

Hypothesis And Objective

Van Helmont pointed out that the growth of plants is due to water intake but not soil or any other food matter. He carried out this experiment to find the contribution of water in increasing the growth and hence the weight of a plant.

Experiment Design

The details are given below:

Materials Used

• A large pot with known weight soil

• Young willow tree

• Distilled water

• Weighing balance of weighing the mass of the soil and pot

• Various water and other maintenance tools for the plant

Procedure

• Weigh the pot and the soil

• Plant the willow tree and weigh the pot with the tree.

• Water the plant regularly with distilled water

• After five years, re-weigh the weight of the pot the remaining soil and the weight of the tree.

Results And Conclusion

Van Helmont found that the willow tree's weight had increased tremendously, meanwhile, the weight of the soil had lost a little. Thereby giving him the reason to think that the gain in weight of the plant was total because of the water since the mass lost by the soil was meagre.

Weight Gain Of Plant

The willow tree grew and its weight increased considerably. His measurements showed that the increase in the weight of the tree was more, relative to the decrease in mass of the soil.

Role Of Water In Plant Growth

Van Helmont's experiment has been an early preliminary discovery of the fact that water is a vital element in plant growth. Unable to present the process of photosynthesis and cellular breathing, his findings insisted on the nature of water and, thus, opened the way for further studies related to the biology of plants and growth processes.

Joseph Priestley’s Experiments (1770s)

The details of the experiment are given below:

Hypothesis And Objective

Joseph Priestley had assumed that plants were able to return "foul" air to its normal condition, again suitable to sustain life. More particularly, he was trying to determine if plants would change the air in so doing, produce a substance in the air that was an essential requirement for respiration.

Experiment Design

Priestley designed an experiment to investigate how plants impact the purity of the air. He took a setup of a sealed container in which a plant with a lighted candle was put and observed a change in the flame in the candle in the presence of the plant and that would help him know if air is getting purified because of plants.

Materials Used

• Glass jar or bell jar (sealed container)

• A plant, for example, mint or other common window plants

• A lit candle

• A pair of bellows to add and remove air (optional)

• Apparatus to measure and observe the flame

Procedure

• Place a lit candle inside a sealed jar.

• Put a plant in the jar and seal it so that no air inside can escape out to the atmosphere.

• Observe the flame on the candle for some length of time recording changes in its nature and flicker.

• After some time, take out the plant and examine the air by blowing out the candle again or using other ways.

Results And Conclusion

Priestley observed that a candle's flame, which became faint and extinguished in the sealed jar, would again be ignited if the plant was part of the equation. Therefore, the plant was releasing some combustible substance.

Priestley concluded that plants develop a principle (it would later be proven to be sensible people also inferred that since plants produced oxygen, then it was an unwholesome gas that harmed life.) This would be the same oxygen that purifies or renovates the atmosphere and that the plants serve as the food of the flame.

Discovery Of Oxygen

Although Priestley conceived of oxygen simply as a gas supporting combustion and respiration and did not consider it an element, his experiments greatly contributed to the discovery of oxygen. His work, at a minimum, thus laid the ground for many later discoveries concerning respiratory gases.

Role Of Plants In Air Purification

Priestley's experiments confirmed that plants clean the air by giving out oxygen and ridding the air of carbon dioxide. This discovery acknowledged the role of plants in providing breathable air and factored in later investigations into the part played by the process of photosynthesis in the quality of air and the state of health of ecosystems.

Jan Ingenhousz’s Discoveries (1779)

The details of the experiment are given below:

Hypothesis And Objective

Jan Ingenhousz hypothesised that green plants produce oxygen only in daylight and thus prepared to demonstrate how light is necessitated in the plant to produce oxygen and whether or not plants photosynthesise in the absence of light.

Jean Senebier’s Contributions (1782)

The details of the experiment are given below:

Hypothesis And Objective

Jean Senebier hypothesised that carbon dioxide is a critical factor for photosynthesis and that plants obtain this factor from the air. He aimed to determine how carbon dioxide functioned in the respiration and photosynthesis of plants.

Nicolas-Théodore de Saussure’s Findings (1804)

The details are given below:

Hypothesis And Objective

It was Nicolas-Théodore de Saussure who first proposed a hypothesis regarding plants: they neither do nor could solely absorb carbon dioxide. However, later he put forth a hypothesis that water could restructure via dissociation into hydrogen and oxygen, which in turn is used to build the plant biomass. His main goal was to assess the contributions of water and carbon dioxide toward the plant growth and formation of organic matter.

Recommended Video On 'Early Experiments On Photosynthesis'