Quercus bicolor, Time of Day, 12 Fall 2016


Question: How does the time of day (morning vs afternoon) affect the photosynthetic efficiency, LEF, phiNPQt, and chloryophyll content in three Quercus bicolor trees? Does the difference in light intensity throughout the day contribute to varying levels of light intensity?

Purpose: We are interested in this question because we want to discover if there is a higher light intensity in the morning or afternoon and how that compares to photosynthetic properties. In a bigger picture, we will take this correlation between light intensity and photosynthesis and use it to compare between U.S. states. This data can help us determine the best place to plant these trees based on the sun’s location and intensity throughout the day.

Hypothesis: The time of day will have an effect on photosynthetic efficiency, LEF, phiNPQt, and chloryophyll content because during different times of day, the intensity of light can be stronger or weaker which is a factor that affects the photosynthetic activity in plants. According to the MAWN, the solar radiation is higher in the afternoon than the morning, this will cause LEF and photosynthetic efficiency to increase and phiII to decrease.

Description: How does time of day (morning vs. afternoon) affect photosynthesis? No other scientists had done research on this topic yet, and this research was important in understanding how trees or plants respond to different intensities of light throughout the day. For instance, planting crops in an open space with no blockage of light intensity from buildings or other factors would improve the plant's growth by exposing it to a greater amount of light. Blackman and Wilson (1996) found that as light intensity increased, so did the leaf-area ratio in “sun” plants; in “shade” plants, reduced light intensity had the same effect. Leaves are the site where photosynthesis begins, and increasing their surface area is of utmost importance in increasing the rate of photsynthesis.

The time of day (morning vs. afternoon) affected the photosynthetic efficiency, LEF, and PQ SPAD in the Quercus bicolor. We hypothesized a higher mean LEF, lower mean ΦII, and unchanging mean PQ SPAD in the afternoon compared to the morning due to the greater light intensity at this time of day. This experiment would be beneficial to other researchers studying how the seasons affect the photosynthetic processes of plants. This experiment would be beneficial to other researchers studying how the seasons affect the photosynthetic processes of plants. It would provide a good basis on how light intensity affects LEF and ΦII and would allow them to expand past what we studied using our findings.

Each tree was divided into four cardinal direction quadrants. Sampling was done in the morning or the afternoon of 15 different days over a seven-week period. Random sampling of 10 exterior, dry, green leaves/quadrant was started in the northwest quadrant then we moved counter clockwise around the trees to collect 40 readings/tree. Repeated random sampling for other two trees. MultispeQ device (Kuhlgert et al., 2016) #127 was placed on the leaf with the white indicator facing up, and the device window placed over leaf area. Used MultispeQ to collect LEF, ΦII and PQ SPAD data. Leaf photosynthesis trace was verified for quality, kept and stored on android device until it was uploaded to PhotosynQ website. Finally, downloaded data and performed independent samples one-way ANOVA comparisons for morning and afternoon per variable based on quadrants/tree, individual trees and combine similar data. Final comparison of time of day for each variable was by two-sample two-tailed t-test for individual samples. Final comparison of time of day for each variable was by two-sample two-tailed t-test for individual samples at vassarstats.net.


  1. We will collect data on three Quercus bicolor trees near North Kedzie hall, with codes 20080316 * 02, 20050351 * 07, and 20050351*08.
  2. We will use MultiSpeQ device #127 to sample each leaf at their natural angles, towards the base of the leaf.
  3. We will divide our tree into 4 cardinal quadrants, NW, NE, SE, SW. We will start in the NW quadrant each time we collect data, and move counterclockwise.
  4. We will choose 10 dry leaves from the exterior of each quadrant of our trees every time we collect data.
  5. Once in a specific quadrant, we will close our eyes and randomly pick a single leaf to sample. Repeat this for 10 different leaves, one at a time, in each quadrant. We will not use a step-stool so we will not have access to leaves at the very top of the tree. We will avoid leaves that are not green and leaves with holes in them. We will not sample wet leaves.

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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. Quercus bicolor tree code was? (Multiple Choice)
  2. What time of day? (Multiple Choice)
  3. Which quadrant was sampled? (Multiple Choice)
  4. Leaf color was? (Multiple Choice)
  5. Which # number leaf was this in selected quadrant? (Multiple Choice)



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