Identifying Plant Stress Using Photosynthesis Measurements

Contributor: Givemore Munashe Makonya   

Measuring photosynthesis provides an insight into how plants respond to changing environmental conditions. But before delving into the specifics, let’s clarify what is photosynthesis and what it truly entails. Essentially, photosynthesis is the conversion of light energy into chemical energy, producing sugars that fuel plant growth and make raspberries and blackberries delicious. However, this process is highly susceptible to environmental factors, making the assessment of photosynthetic rates a prime indicator of a plant’s stress levels . For example, if weather is too hot and exceeds the optimum or maximum temperatures for photosynthetic efficiency, photosynthesis will be reduced or even may shut down.  

Measuring photosynthesis can be done using different techniques. The first way  to measure photosynthesis is through gas analysis. A CIRAS or LI-COR portable photosynthesis gas analyzer is a device that is used to measure gas exchanges between plant tissues (e.g., leaves) and the ambient environment.  This analysis works by comparing carbon dioxide uptake and oxygen production rates over time (mention of trade names is not an endorsement or promotion). 

A portable photosynthesis machine that measures gas exchange between leaves and the environment.
Portable photosynthesis machine that utilizes spectroscopy shown above

A second technique is spectroscopy and it can be used for multiple applications.  Some examples of spectroscopy measurements are orientation of pigments in the plant, monitoring of plant tissues and reactions of short lived intermediates (Espinosa-Calderon, et al., 2011). The variety of spectroscopy methods makes it possible to collect a vast variety of data.  

Depending on what data are needed, measurements are taken at different points along the photosynthesis cycle. Therefore, it is common to use multiple techniques at different stages of photosynthesis. This is to build a more complete understanding of the plants and their productivity. 

To interpret the data collected, control data is necessary. Reference data can be found in existing publications. It is needed because reference data provides expected values under ideal conditions. This allows for accurate conclusions to be drawn from the measured data. Once control data are acquired, comparisons between the measurements and reference data can be made. 

The information that photosynthesis measurements provide allows for a better understanding of plant physiology, which is very important when assessing plant stress in response to different treatments.


  1. Espinosa-Calderon, A., Torres-Pacheco, I., Padilla-Medina, J. A., Osornio-Rios, R. A., Romero-Troncoso, R. de J., Villaseñor-Mora, C., Rico-Garcia, E., & Guevara-Gonzalez, R. G. (2011). Description of photosynthesis measurement methods in green plants involving optical techniques, advantages and limitations. African Journal of Agricultural Research, 6.