Introduction: This study was valuable because it is something that other researchers have asked questions about leaf senscence but have not collected data from trees like we did . In fall, trees went through a variety of phenological changes which we were curious about how leaf photosynthesis was affected.
In deciduous trees, autumn phenology includes leaf senescence that resulted in changes to leaf color from green to yellow and/or red, which eventually led to leaf abscission. Leaf senescence also includes down regulation and cessation of photosynthesis that eventually indicated the end of the growing season (Junker & Ensminger et. al., 2016). Our research looked at the leaves as they were going through senescence.
According to Knipling (1970), biological disturbances, the later on which the trees were located and physiological disturbances had a big effect on the color of the leaf. Schmaefky et al. (1998) shows how color changes of leaves had an ecological and physiological impact. We measured three variables of photosynthesis in leaves. PQ SPAD measured the chlorophyll content while ΦII measured the efficiency of the photosynthesis at PSII and LEF measured the transfer of chemical energy. The research objective was to show the effect of color change on mean PQ SPAD, mean ΦII and mean LEF in Acer truncatum x plantanoids as the fall progressed.
Overall, our hypothesis was that photosynthesis variables would be higher in green leaves and lower in leaves with less green color because as green leaves have more chlorophyll and capture more energy so as leaves senescenced and changed from being green they contained less chlorophyll and captured less energy for ΦII and LEF.
This will advance research being done by quantitatively showing that green leaves contain the highest amount of PQ SPAD, ΦII, and LEF then senescencing leaves change color and enhance researchers understanding of the yearly phenological processes.
Methods: Acer truncatum x platanoides Trees.These three biological sample replicates were studied and coded 93P00412 (a), 93P00410 (b), and 93P004*09 (c). All three trees were planted in 1993 on the campus on Michigan State University just northeast of the Benefactor’s Plaza.
Sampling Methods. Each three was divided into the four cardinal direction quadrants, shown above. Data was collected in the northwest quadrant and moving clockwise collected in northeast, southeast, and ending in southwest. The MultispeQ device (Kuhlgert et. al., 2016) #121 was clamped onto the center of a dry exterior leaf and held steady to measure PQ SPAD, ΦII, LEF levels, illustrated in the measurement trace. Also, recorded leaf color. Ten leaves were measured in each quadrant totaling 40 leaves/tree for a total of 120/day. Daily, data was recorded on the tablet until it was uploaded to PhotosynQ website. After 7 weeks, thirteen different days of data was downloaded and analyzed with one-way ANOVA for independed samples of leaf color by comparing quadrants/tree, individual trees and finally by different leaf colors at vassarstats.net. Thanks to Steven Haydon for helping us collect data once.
- 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
- Which Acer tree code? (Multiple Choice)
- What quadrant sample? (Multiple Choice)
- Leaf color was? (Multiple Choice)
- Leaf count (Multiple Choice)