The Process Of Photosynthesis And The Factors Influencing It

Plants are considered as autotrophs because they use energy from sunlight to synthesize their food source. They use sunlight, water, and carbon dioxide to form glucose, which is necessary for them to survive. This process is called photosynthesis.    

Photosynthesis is the process in which plants transform light into chemical energy. It captures the energy from sunlight to make sugars that store chemical energy. The whole process of photosynthesis is a transfer of energy from the sun to the plant, therefore; the energy from almost all organisms comes from sunlight.    

The origin of the word photosynthesis comes from the word photo which is a Greek word for light and the word synthesis which means to build, so plants use light and small molecules to build a larger molecule that metabolizes to produce energy. Photosynthesis is important to maintain life on earth, it is the number one source of oxygen in the atmosphere. Without photosynthesis, there would be no food on earth, the carbon cycle will not occur, and all plants would die. Therefore, directly or indirectly photosynthesis affects most life on earth. The development and study of photosynthesis started in 1771 with observations by the scientist Joseph Priestley. It started when he burned a candle in a closed container until the air within it couldn’t support combustion any longer. After he placed a spring of mint plant in the container, after several days he discovered that the mint has produced oxygen that enabled the confined air to support combustion.    

Later, in 1779 the physician Jan Ingenhousz expanded on Priestley’s work by showing that the plant had to be exposed to the light of oxygen was to be restored. Also, he mentioned that this process required the presence of the green tissue of the plant.    

In 1804, gas-exchange experiments showed that the gain in weight of a plant grown in a pot resulted from the uptake of carbon, which came from absorbed carbon dioxide and water taken up by plant roots, and it is balanced when oxygen is released back to the atmosphere. In 1845, they discovered that light energy from the sun is stored as chemical energy in products formed during photosynthesis.    

During photosynthesis, the molecule in leaves capture sunlight and energize electron that will be stored in the covalent bonds of a carbohydrate molecule. Moreover, the energy within the covalent bond will be released during cellular respiration. Photosynthesis consists of two stages.    

Stage one is the light reaction, in which solar energy is converted into chemical energy and stage two is the Calvin cycle which uses the chemical energy from stage one to build G3P (glucose precursor) to glucose and other molecules. Both of these stages occur in the chloroplast. A chloroplast has two membranes that surround a fluid called stroma within which sacs called thylakoids are suspended. These sacs are often stacked in columns called grana, and in the membrane of these thylakoids sits a special pigment molecule called chlorophyll. Chlorophyll can take either an A or B form differing only in one functional group inside the porphyrin ring, either a methyl or aldehyde group. The porphyrin ring is what gives this molecule the capacity to absorb sunlight uniquely.    

The overall reaction of photosynthesis is summarized in the following equation: 6 CO2 + 6 H2O + light → C6H12O6 + 6 O2 Carbon Dioxide + Water + light → Glucose + Oxygen Light

Factors that influence the rate of photosynthesis:  

• Light Intensity: The plant won’t be able to photosynthesize quickly without light, even if there is a huge amount of water and carbon dioxide. The relation between light intensity and the rate of photosynthesis is directly proportional because when the light intensity increases the rate of photosynthesis will increase too.  
• Carbon Dioxide: If there is insufficient carbon dioxide in the air the photosynthesis cannot occur at the maximum rate. However, if the concentration of carbon dioxide increased, the rate of photosynthesis will increase.  
• Temperature: Plants are sensitive to temperature, if the temperature is too hot they cannot photosynthesize and if the temperature is too cold their productivity slows down to zero. This is because there are enzymes involved in photosynthesis, so about 40 degrees Celsius the enzyme starts to denature and so the rate of photosynthesis slows down, and as it gets cooler the enzymes move around slowly and hence the rate of reaction drops. Different types of plants have different optimum temperatures for photosynthesis; for example, plants that live in colder climates have an optimum rate at a lower temperature.  
• Water: water is very important for photosynthesis and a shortage of water decreases the rate of photosynthesis. Only a small percentage of water absorbed by the plant is used for photosynthesis and the rest is lost due to transpiration.  
• Minerals: water and carbon dioxide are absorbed through the roots as the mineral ions dissolve in the solid water. The two important mineral ions that plants needs are nitrate and amino acid. If the plant does not get enough minerals, its growth will be poor.  
• Leaf anatomy: Many factors of leaf anatomy affect the rate of photosynthesis such as the leaves thickness of the epidermis, the different sizes of the intercellular spaces, the different positions of stomata, and the different types of chlorenchyma and the vascular tissues.  
• Chlorophyll: Chlorophyll is essential for photosynthesis. There is a direct relationship between the amount of food formed and the chlorophyll content.    

In conclusion, photosynthesis is an important process for many reasons. Human, animals, fungi, and some microorganisms cannot make their own food like autotrophs, but they still rely on photosynthesis, that’s why photosynthesis is the basic food chain for all organisms. In addition, plants release oxygen into the atmosphere and almost 90% of oxygen is from photosynthesis which leads to a fact that photosynthesis is one of the most important processes in the world.