Investigation of rates of photosynthesis and limiting factors



Investigation of rates of photosynthesis and limiting factors

Introduction

Photosynthesis is a process in which plants capture energy of light and make life on the planet of earth possible. An understanding of the factors that affect the rate of photosynthesis holds crucial importance in order to guarantee that a sufficient supply of food or energy is available for the survival of living things. The process of photosynthesis is affected by two groups of factors, namely internal and external factors. The internal factors are plant related factors whereas the external are environmental factors. The internal factors include the protoplasmic factor, accumulation of byproducts and internal structures of leaf. The external factors include intensity, wavelength and duration of light along with carbon dioxide concentration levels, variations in temperature and water availability to plants. These factors increase or decrease the rate of photosynthesis depending upon their optimum values. In 1905, Blackmann created a law of limiting factor. According to this law, the process of photosynthesis is limited by one of the most limiting factors. This is the factor that evaluates the rate of the process of photosynthesis.

Discussion

Measuring Photosynthesis

The rate of the process of photosynthesis is measured as the quantity of the gas of carbon dioxide absorbed by a plant per unit time. It can also be measured by the quantity of carbohydrate that is formed per unit time. In investigations of laboratory, the rate of photosynthesis is measured as the quantity of oxygen that is released per unit time (Toole & Toole, 2004, p. 30). This method is a more practical one for the measurement of this rate. But this method does not yield accurate results as oxygen is released by plants during respiration process as well. To overcome this fact, the rate of photosynthesis is measured above the compensation point. The compensation point is a point at which the rate of respiration and rate of photosynthesis get balanced together. At this point, there is no net exchange of oxygen and carbon dioxide. This point is mostly related to a specific carbon dioxide concentration level or specific light intensity. This compensation point varies for various species.

Factors that affect the rate of photosynthesis

There are many factors that affect the rate of photosynthesis. The factors are external as well as internal. The external factors are those that are present in the environment whereas the internal factors are the ones that are present inside the plant (Kent, 2000, p.94). The external factors consist of intensity of light, light`s wavelength, varying levels of carbon dioxide, temperature, mineral supplies, water and velocity of the wind. The internal factors consist of concentration and type of pigments of photosynthesis, leaf structure and position, water and enzyme content.

Quantitative determination of the impact of these factors is difficult to carry out. The reason for this is that these factors interact with each other and have an impact on the other plan processes. For instance, the significance of the factor of water for the process of photosynthesis ...