Dimitrova V. and Gineva G.

How do different liquids affect plant growth?

The main job of photosynthesis in plants is to convert light energy into chemical and therefore create nutrients, such as sugar molecules, which fuel the organism. These supplements are vital for the life of a plant and probably each one of us has wondered what will happen if we externally add more nutrients. In our science fair project we did an experiment using hyacinth bulbs and watered them with five different liquids (water as our control group), Coca Cola, Energy drink, 100% Multivitamin Juice and Nescafe 3 in 1. Each plant was ensured to obtain the same amount of sunlight and fertilizer.

The results, as we expected, were that the plants irrigated with energy drink and multivitamin juice died and developed mold, the coke one also died but slower than the other two and surprisingly the coffee plant started growing at first, but later on we observed that it died, too which is a result of the overload of caffeine which started to eventually kill the cells. Even though they contain vitamins and minerals, the redundant amount of sugar creates a hypertonic solution in the plant cells and therefore prevents them from absorbing the nutrients that are supposed to stimulate its growth. This led us to our second experiment which included the same plants,the same conditions and the same liquids but diluted with 75% water. The only plant that grew was coffee which was smaller than the control group but still made some progress while the others didn't.

We observed that diluted coffee might replace water and have similar effects on plant growth but overall it did not show any benefits which is why we believe that water is still the best liquid to water plants with.