Back in November, I explored Shanghai's parks and came upon a beautiful Japanese Maple.
I was fascinated by how the leaves bright orange colors were in stark contrast to their natural backgrounds, so much so that I decided to take a sample of a leaf and bring it back to my dorm for further examination.

After I had prepared the slide and positioned under the foldscope, I was amazed by the resulting micrograph.

{Japanese maple leaf 140x}

I was utterly mesmerized by the bright oranges and reds found in this micrograph but I wasn't privy to the reason as to why they were present. During the initial exploration, I didn't dive deep in the reason why these pigments were present, however the objective of this project was to understand both what these pigments were and how or if they correspond to temperature change.

Upon further research, I discovered that the pigments that resulted in the red, orange, and yellow colors were from anthocyanins situated within the cells vacuoles.

Anthocyanins offer multifaceted, versatile, and effective protection to plants under stress, acting as the Swiss army knife of the plant kingdom. They have been shown to reduce both the frequency and severity of photoinhibition, the decline in the quantum efficiency of photosynthesis, as well as to expedite photosynthetic recovery. Specifically, when leaves are exposed to more light than natural, the efficiency at which they can perform photosynthesis decreases.



What this graph shows is the drop in efficiency for plant leaves as they're exposed to more light than natural. One can observe that the leaves with anthocyanins were able to process significantly more light than those without. More importantly, the rate at which the leaves were able to return to their previous photosynthetic efficiency was dramatically increased by the presence of anthocyanins.The reason for this is that their darker red pigments are able to diffuse the incoming light, thus preventing photoinhibition.

{Anthocyanins pigments being released in flower stem cells}

The reason why anthocyanins appear in increased quantities during winter is because low temperatures during winter lead to decreased fluidity of plant cell membranes, decreased activity of enzymes, oxidative stress, and the accumulation of reactive oxygen species (ROS). The molecular structure of anthocyanins allows them to neutralize ROS through electron donation, thereby interrupting the chain reactions that lead to oxidative damage.


{Molecular structure of anthocyanins}

This December I revisited the exact same Japanese Maple and captured a drastic change in the color of its leaves. In just under a month, the leaves had transformed into a beautiful cherry red. I was happy to find that the theoretical findings were beautifully visualized in the leaves transformation.


{Japanese Maple in December}

These changes were even more vivid within the micrographs, where the accumulation of anthocyanins could be easily seen.


{December micrograph of Japanese Maple 140)

Overall, I'm incredibly happy with the learning outcomes of this experiment. Not only did I obtain a more concrete scientific understanding of why leaves change color, but more importantly, an appreciation for the microscopic beauty of nature.