Disease, Damage, and Drought: Impacts on Photosynthesis



  • How does photosynthesis and other measurements change in diseased, damaged, and otherwise unhappy plants?

  • What diseases impact photosynthesis, and how do they do it?

  • Is it possible to identify the onset of diseases (especially non-visible diseases like root rots) using photosynthesis measurements?


The goal of this project is to survey of ‘unhappy’ plants and comparison to similar ‘happy’ plants to identify the ways in which photosynthesis changes based on different types of disease, drought, and damage. By collecting information from many environments across the world, we may be able to develop early predictors of these stresses and better understand how plants adjust and defend themselves.


NOTE: Make sure NOT to measure holes or tears directly - if there are physical holes measure right next to the hole, not on top of it. Ideally, each measurement should be on a slightly different part of the leaf, or different leaves all together.

  1. Measure a diseased plant or leaf 5 times.
  2. Measure a healthy leaf 5 times on the same plant, or a plant of the same species nearby.

You'll also need to know roughly what has damaged the leaf. Here are some examples:


Viruses, bacterial, and fungal- including root rots not visible on foliage



Insects and pest animals



Frost, drought, heat, wind, and flooding



Gonstruction, human, and other physical



Leaf Photosynthesis MultispeQ V1.0


Measures many photosynthesis-related parameters in <15 seconds, including:

  • Chlorophll Fluorescence: Phi2, PhiNPQ, PhiNO, NPQt, qL, LEF
  • Relative Chlorophyll: SPAD
  • Proton Motive Force: ECSt, vH+, gH+
  • Absorbance at: 450, 535, 605, 650, 730, 850, 880, and 940nm.
  • Leaf Thickness (in mm), angle, and cardinal direction
  • Leaf Temperature and differential from ambient temperature
  • Environmental conditions: PAR and ambient temperature/pressure/humidity


It's not practical to fully describe what all of these measurements mean here. If you want to learn more, a good place to start is this video: https://www.youtube.com/watch?v=pU5vOtE1wE8 . Check the PhotosynQ youtube channel for other videos explaining photosynthesis and related parameters.

This article is also helpful http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3040.2007.01680.x/abstract. It's paywalled, but email admin@photosynq.org to request a copy.

If you want to see the exact calculations for each parameter, please see the associated macro called "Leaf Photosynthesis MultispeQ V1.0".

Finally, there are two publications about the MultispeQ Beta device covering many of the below parameters and comparisons to commercial instruments. While that is technically an older model device, the calculations and comparisons are still true for this protocol. You can find them at the Royal Society for Open Science, and <still waiting on this one!>.

_Works with the MultispeQ V1....


  1. Plant Type
  2. Plant Height
  3. Optional: Genus and Species (lowercase)
  4. Leaf Condition
  5. Optional: Disease or Pest Name
  6. Leaf Location
  7. Leaf Image
  8. Leaf Number (Use Auto Increment)



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By Greg Austic, 9 months ago
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