Why do some plants die at the very first frost, while others calmly endure the Yakutian winter with temperatures dropping below minus fifty? The answer lies in ordinary water — or rather, in how remarkably different it can be inside living plant cells and tissues. Scientists distinguish two fractions of water in plant tissues: free and bound. Free water behaves just as we expect: at zero degrees Celsius it turns into ice, and the resulting crystals rupture delicate cell membranes from within. Bound water, on the other hand, is tightly held by proteins, sugars, and starch molecules and does not freeze even at minus twenty degrees or lower. This "unfreezable" fraction acts as a natural antifreeze and largely determines whether a plant will survive a sudden cold snap or not.

But how can we measure exactly how much bound water is present in a birch leaf or a lingonberry twig? In well-equipped laboratories, researchers use a differential scanning calorimeter (DSC) — an instrument that detects the tiny amounts of heat released during freezing and can thereby separate free water from bound water. The problem is that such a device costs millions of rubles and is completely inaccessible for a school laboratory.

In our project, we propose a different path: to build such a calorimeter ourselves, using affordable and widely available components. The heart of the device will be an Arduino board, while high-precision TMP117 digital temperature sensors, capable of detecting temperature changes as small as one-tenth of a degree Celsius, will serve as its accurate electronic "eyes." We will cool our samples using Peltier elements — the same ones found in portable car refrigerators — or possibly an ordinary freezer. Project participants will assemble the electronic circuit with their own hands, write a sketch to simultaneously poll several sensors, build a thermostatted measurement block, and calibrate the instrument using pure water.

During the experiment, the sensors will continuously record the temperature, and right before our eyes the laptop screen will begin to display thermograms — graphs on which the freezing of free water appears as a characteristic crystallization (freezing) peak. This peak holds the key information: its area is proportional to the amount of heat released during ice formation, and therefore to the mass of free water in the sample. Bound water, in this temperature range, remains liquid and produces no signal at all. We will determine the total water content by drying the samples and measuring both fresh and dry weight. By comparing the results for different species and different plant organs, we will try to answer the question: which plants are better prepared for sudden frosts, and why? Perhaps lingonberry will prove to have more bound water than plantain, or roots will differ from leaves.

Participant requirements:
This project is for those who want to do more than just listen — they want to build things with their own hands and immediately see how they work. Into electronics and soldering? You will assemble the circuit and tune the sensors. Enjoy coding? You will write the Arduino sketch. Love biology and hiking in the forest? You will collect plant samples and help interpret the results. Prefer numbers, graphs, and finding patterns? You will analyze thermograms and calculate how much water has frozen. Through the coordinated efforts of the team, we will assemble a real scientific instrument, obtain new data on Yakutian plants, and gain a better understanding of how they prepare for the harshest winter on Earth. Join us!