Plant Height & Photosynthetic Characteristics


The influence of plant height on photosynthetic characteristics (PQ SPAD, LEF, Phi II) will be analyzed by comparing these traits between a Hydrangea Bush and a Red Maple (Acer rubrum) tree.

Project Description:

Introduction: Photosynthetically active plants are necessary for any type of horticulture that is being done and being able to measure this is key in order to see how they will produce in the future. The study that we conducted was to look at leaves on specific plants and measure their photosynthetic activeness. We did this study to be able to compare the differences in heights in plants to see if there was any difference this caused for their stress and activity. The device, MultispeQ, uses a modified version of the SPAD parameter to estimated relative chlorophyll content by measuring the relative transmissions of red (650 nm) and infrared (940 nm) light. Relative chlorophyll content (SPAD) is broadly used as an indicator of plant nitrogen status as well as the onset of diseases or other stresses. (Kuhlgert) This research was to prove or disprove the possibility of height affecting the photosynthetic activity on leaves.

Hypothesis Development/Goals: The hypothesis that led the group to the research was designed to look at the height of plants and to see the influence of height on different photosynthetic characteristics. It seemed that the shorter bushes were not as photosynthetically active at the start of the research which led to believe that the taller plants would have greener leaves. The expected outcome was that the taller the plant, the more likely it was going to be that the photosynthetic features are going to be more photosynthetically active.This experiment was important to us because being able to look at the plants and figure out which of them was most photosynthetically active could potentially help other researchers with their future endeavours in looking into the possibility of genetically modifying plants in order to make them more likely to produce crop or anything of the sort that they are trying to produce.

Hypothesis: Plant height would affect the photosynthetic characteristics because Acer rubrums have less distance to the sun and Hydrangeas are closer to the ground

Predictions: LEF, PQ SPAD, and ΦII are all smaller in Hydrangea bushes than in Acer rubrum trees

Methods: Samples (n=1,080) were taken from Acer rubrum trees (n=3) and Hydrangea bushes (n=3) in the Benefactor’s Plaza at Michigan State University. In order to ensure random sampling trees and bushes were divided into quadrants (SE, SW, NW, NE). Data was collected starting in the SE quadrant moving in a clockwise pattern ending in the NE quadrant, collecting 5 leaves per quadrant. This was repeated for 9 sessions, resulting in a total of 180 samples per plant. Eac measurement session took place between 11:30am and 2:30pm. A MultispeQ device was used to collect the plant performance (SPAD, LEF, ΦII). Data was uploaded to PhotosynQ and we were able to view graphs and data points that analyzed the SPAD, LEF, ΦII and PAR of the leaves. To analyze the data collected through PhotosynQ, three one-way ANOVAs were used.

Random Sampling Method: MultispeQ device #123 and tablet #5 were used for measurement. As stated above, random sampling was ensured by splitting each plant into four quadrants: SE, SW, NW, NE, and randomly selecting 5 leaves from each quadrant during each section of measurement, for a total of 180 samples per plant. Furthermore, measurement was split up among four experimenters to avoid user error/bias, with each group member taking 270 total samples.


Leaf Photosynthesis - MultispeQ Beta ONLY

Measures photosynthesis-related parameters in <15 seconds, including: Phi2, PhiNPQ, PhiNO, NPQt, qL, LEF, and SPAD. In addition, measures PAR (photosynthetically active radiation), ambient temperature and relative humidity.

Works with the MultispeQ Beta device only


  1. Which organism is this? (Multiple Choice)
  2. Which quadrant of the plant is being measured? (Multiple Choice)
  3. What is the (random) sample count within the quadrant? (Multiple Choice)



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