Plants in our life
Did you know that plants are our main source of life? They filter our air by consuming toxic CO2. Together with the water they drink from the ground, plants can convert energy captured from sunlight into sugars, for us to eat, and oxygen, for us to breath.
This process is known as photosynthesis:
Besides serving us as the main source of energy in the form of fruits or vegetables, plant products are essential resource for human well-being. They include wood, oils, pigments, fibers. Even our technology is driven by plants as coal and petroleum are fossil substances of plant origin.
Sensing the surrounding
Plants live in an ever changing and, at times, a challenging environment, which can dramatically interfere with the process of photosynthesis. Within one day sunny dry conditions can become dark and wet. It is fascinating how plants are able to sense and adapt to such changes. When water becomes available, plants quickly take it up, and when sunlight becomes too intense, plants protect themselves. You have probably also observed that plants grow towards light. However, did you ever wonder what mechanisms govern their behaviour? Have you ever wanted to see plants produce oxygen? Here we suggest a few experiments you can do at home to enable you to witness and understand the science of how plants sense their environment.
Experiment Nr 1: Osmosis
Like us, plants need water to survive. They use osmosis to absorb it together with nutrients from the soil. By definition, osmosis is the movement of water molecules from an area of high water concentration to an area of low water concentration through a partially permeable membrane.
The cell membrane of the root hair cell acts as partially permeable membrane and because the cell sap inside the vacuole has low water concentration water passes from the soil into the root hair. The concentration of the sap in the vacuole is now weaker as there is a high concentration of water. Water will now pass from this area to the next cell with lower concentration and will continue to move along the cells of the root up the xylem to the leaf.
By colouring the water in which the plant sits in, we can observe how petal turns colour and that water in fact travels up a plant’s xylem.
Experiment Nr 2: Fluorescence
Since plants need light to carry out photosynthesis, if we provide the plant with light, it should be able to make more oxygen and sugar, right? Not at all!
Actually, plants cannot cope with too much light! To deal with the excess light energy, they release the surplus energy by re-emitting tiny red signal called fluorescence, which is normally invisible to our eyes.
In an experiment, we show how plants protect themselves by re-emitting a part of the UV-light shone on them in the darkness, where photosynthesis process was blocked.
Experiment Nr 3: Gravitropism
It is a general feature of all higher plants that roots grow in the direction of gravitational pull (i.e., downward) and stems grow in the opposite direction. When the seed is in the soil, it is dark and not easy to find where the surface is. Plants can sense gravity to help the germinated seeds change shoot growth to the ‘upwards’ direction and root growth ‘downwards’. Growth movement in response to gravity is called gravitropism.
To investigate gravitropism in shoots and plant movement towards the light you can built the onion tower that at the end of the experiment may serve as a supply of onion greens for whole family.
Experiment Nr 4: Oxygen production
Would you like to witness how plant absorbs CO2 and produces oxygen, using quite similar set up as famous scientists Joseph Priestley?
Alone in a sealed jar, with no source of oxygen a burned candle would produce hot carbon dioxide that would accumulate at the top of the jar, pushing down other gases like oxygen and eventually stifles the flame.
Remembering that plants breath the CO2 and produce oxygen in turn, place a plant and candle under a large jar and after a month light up the candle inside to observe that level of oxygen produced inside is sufficient to allow the candle to continue to burn.