How are photosynthetic efficiency, linear electron flow, phiNPQ, and chlorophyll content affected by the location of the leaves within the canopy (exterior or interior of the canopy) in A. rubrum trees?
The ability for leaves to perform photosynthesis is vital to their survival. Photosynthesis is the ability for plants to convert light energy into chemical energy. Some leaves are hidden from the sun, while other receive the full benefit of sunlight for their photosynthetic processes. According to Henriot et al. (2004), the upper and exterior parts of the leaves receive 70-80% of the available Photosynthetically Active Radiation (PAR) and show better photosynthetic rate than the leaves in the lower or intermediate positions, receiving 10-40% of the available PAR. This study shows that there are differences in photosynthetic abilities based on the location of the leaves. Kuhlgert et al. (2016) also released a recent study highlighting the features of the MultispeQ Beta device and its technological importance in taking measurements of leaves. Does the placement of the leaves within the canopy impact their photosynthetic ability? Are the exterior leaves more photosynthetically active than the interior leaves? Our topic of research is to compare the differences between the location of the leaves within the canopy (interior vs. exterior) and its corresponding effect on the photosynthetic effieciency (phiII), LEF, phiNPQt, and chlorophyll content (PQ SPAD 3) of A. rubrum *trees. This is important in efforts dedicated to discovering if sunlight plays a role in the photosynthetic activities of interior and exterior leaves.
Our research hypothesis is that the leaves on the exterior of the canopy will have greater photosynthetic activity than the leaves on the interior of the canopy due to their increased exposure to sunlight. We expect phiII, LEF, phiNPQt, and PQ SPAD 3 will all have an increase in their values in the exterior canopy compared to the interior canopy of the tree. With this outcome, this will allow scientists to conclude that the amount of sunlight plays a major role in the resulting activity of leaves. This result will support previous findings, like Hollinger (1989), who showed that leaf photosynthetic capacity decreased as the depth of the canopy increased.
Random Sampling Method Using a MultispeQ Beta device (#222) and Samsung Tablet (#8), we will gather the photosynthetic efficiency, linear electron flow, phiNPQ, and chlorophyll content of leaves on the interior of the canopy and compare them to the exterior of the canopy in A. rubrum trees.
This is a project other people can partake in, as long as they follow the protocols listed below, use the same materials, have the same controlled variables, and measure the same variables listed above in other A. rubrum trees. Other results may differ from ours due to a change in sunlight exposure, time of year, time of day, and other variables that may not be able to be controlled.
In total, we will be studying three 9 year-old biological replicate A. rubrum trees located in the Benefactors' Plaza at Michigan State University in East Lansing, MI.
We will select leaves from the exterior of the canopy from the entire perimeter and will select leaves from the interior of the canopy from the entire circumference closest to the trunk.
The leaves from the exterior of the canopy will be within 1 foot of the furthest extension of a branch for the entire circumference of the tree. The leaves from the interior of the canopy will be within 1 foot of the trunk for the entire inner circumference of the trunk and leaves.
The tree will be split into 4 quadrants—north, south, east, and west—for the exterior and the interior of the canopy, using the compass provided on the map.
We plan to collect 120 samples/sampling day. We will go out into the field in pairs and each partner will collect 60 samples. For our 3 trees, we will collect 40 samples from every tree—20 samples per a person. Since there are 4 quadrants on each tree, 10 leaves will be sampled from each quadrant, 5 on the interior and 5 on the exterior. In total, 1,440 data points will be collected over a course of 4 weeks.
We will work clockwise from north to east to south to west. For each tree, 10 samples will be collected in each quadrant, 5 from the exterior and 5 from the interior. In order to reach the green exterior leaves, we will use a step stool (and a ladder, if needed). The exterior leaves will be within 1 foot of the outermost leaves and the interior leaves will be within 1 foot of the trunk. From there, remaining unbiased, we will close our eyes and randomly select 5 green, photosynthetically active leaves. If a leaf with holes, or a dead leaf is selected, we will re-select due to the lack of photosynthetic activity.
After gathering our data points, we will flag outliers and perform a series of ANOVA tests to discover which quadrants and trees are not significantly different. Once the trees/quadrants are classified as not significantly different categories for each variable, a t-test will be conducted. This will render whether the difference between the the exterior and interior leaves supports our hypothesis or not.
- 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
- Acer rubrum tree code was? (Multiple Choice)
- Which quadrant sampled? (Multiple Choice)
- Location in canopy? (Multiple Choice)
- Randomly selected leaf counted in the quadrant/location-# count? (Multiple Choice)