Where does the water go? that is the question that I asked my students Monday when we started our lesson about transpiration. We water, water, and water plants all the time, but what happens to the water? We decided to answer this question by using celery.
Day 1 - Weight the celery
Students were able to figure out that the plant itself uses the water, but how do we know for sure? The only way to figure this out would be do leave the celery in water for 24 hours and do before and after weights of the celery. Students filled two vials with 20 ml of water and place celery in one vial and nothing in the other, to test evaporation.
Day 2 - Results and further investigation
On day 2 we found that our celery had increased in weight considerable and the water levels have gone down by half in most celery vials. As for the water vials, there was little to no change, ruling out evaporation. Next step? Next we want how the water is being disturbed inside the plant, we already know about water channels but where exactly do they go? To find out we added red dye to our water and waited another 24 hours.
Day 3 - Finding water channels and understanding transpiration
We found a surprise with our celery. Many of the leafs have turned a reddish color and we are starting to see red lines in our celery. We have discovered that these water channels feed water to all parts of the plant including the leafs, we know this by the the red lines that are visible in the celery (just like the one on your left). Next question, what is the next step in the water process? The answer, transpiration. Students learned that transpiration is the evaporation of water from the aerial parts of plants, especially leaves but also stems, flowers and roots. So if this is correct we should be able to visually see this process by placing a plastic bag over a tree or shrub branch, students came up with the hypothesis that water will collect on the inside of the bag.
Day 4 - Results and finally conclusions
On day four we discovered that our hypothesis was correct! We found that there was all kinds of moisture on the inside of the bag. Turns out that the water is released from the plant in a gas form through little pores in the leaf called stomates. Let's recap for a moment, the process of transpiration goes like this:
Water is first absorbed by the roots, passes through the plant through channels, and then is released as a gas through the plant's leaf surface. Next step for us is flower reproduction.