Question

Shown below is graphical representation of stomatal conductance, water evaporation and Co2 assimilation as function of 24 hour cycle. Which plants show this type of response? Explain. The effect of light intensity, amount of carbon dioxide and temperature on rate of photosynthesis was studied. The results of the experiment were plotted in a graph as shown below. Comment upon the factors that affect rate of photosynthesis.

Answer 1

Amount of CO2 and the rate of photosynthesis:

In general, carbon dioxide is found in low concentration in the atmosphere, and so atmospheric carbon dioxide levels may be a major limiting factor on photosynthesis when at low levels. As carbon dioxide concentration increases, the rate of photosynthesis increases. At high concentrations, the rate of photosynthesis begins to level out due to other factors not related to carbon dioxide concentration becoming limiting (Science Hally hosting).

Light intensity:

Light intensity directly affects the light-dependent reaction in photosynthesis and indirectly affects the light-independent reaction. Light is a limiting factor when the light intensity is too low to allow the light-dependent reaction to proceed at its maximum rate. Light is not normally a limiting factor except for plants in forest understory of other shaded plants. Very high light intensities may slow the rate of photosynthesis due to bleaching of chlorophyll.

As light intensity increases (distance between lamp and plant decreases) the volume of oxygen (or the rate of bubble production) increases. This indicates that the rate of photosynthesis increases with light intensity. However, at sufficiently high levels of light intensity, the rate oxygen evolution remains constant (Brilliant Biology Student).

Effect of temperature

At low temperatures, between 0 and 10 degrees Celsius (32 and 50 degrees Fahrenheit), the enzymes that carry out photosynthesis do not work efficiently, and this decreases the photosynthetic rate. At medium temperatures, between 10 and 20 degrees Celsius (50 and 68 degrees Fahrenheit), the photosynthetic enzymes are working at their optimum level, so the rate of photosynthesis is high. At temperatures above 20 degrees Celsius (68 degrees Fahrenheit) the rate of photosynthesis decreases as the enzymes do not work as efficiently. This is also despite the increase of carbon dioxide diffusion into leaves. At a temperature above 40 degrees Celsius (104 degrees Fahrenheit), the enzymes that carry out photosynthesis lose their shape and functionality, and photosynthetic rate declines rapidly (Synonym).