This deceptively simple task could provide useful diagnostic information near the start of a unit. Several misconceptions (or gaps in conceptions) were revealed during the trial of this task.

Sources of energy
Students were asked to say how plants get energy. Some thought this came from the rain, or that "rain feeds the plant". Others said that the roots get their energy from the soil (or, they might say they get "food" from the soil). Research shows that seeing the soil as a source of plant food is a common misconception. It is reinforced by the everyday use of terms such as "plant food" with reference to fertiliser or humus.
Students need opportunities to explore differences between nutrients and energy to untangle this misconception, especially as it is so widespread in everyday talk.

Many students made an implicit connection to the sun (as indicated by its inclusion in the diagram) but did not explicitly state it as an energy source. Very few students named photosynthesis as the means by which plants acquire energy in a form they can use for growth, let alone explained it. Some students hedged their bets by naming all three as potential sources – "energy source = sunlight, rain, soil".

Role of the seed as an energy source
Very few students appeared to realise that seeds provide the initial energy for growth and that, as this is used up, seeds shrivel up. This can be directly observed if large seeds like beans are germinated in conditions where the changes are visible (e.g., between a sleeve of moist paper and the side of a jar, with soil or damp sawdust inside the paper sleeve). Role of the roots
Some students saw the roots as the source of energy for the growing plant.

• "energy is stored in roots"
• "seed gains energy from the root"

Some energy is stored in roots, for example in deciduous trees as they over-winter. It is possible that what students have in mind is sources of their food that come from under the soil. But these are more likely to be forms of underground stems (e.g., rhizomes and tubers) than roots. Students need to appreciate that this is a specialist adaptation of some roots or stems and is not the norm. They could investigate examples of foods we eat that originate this way.

Taking a systems approach
The raw materials absorbed by the roots, including both soil nutrients and water, are needed for photosynthesis. But the process cannot proceed without energy from the sun and the specialist structures and chemicals produced in the leaves (and in some cases in green stems). Appreciating that all these parts have to work together to provide energy in a form the plant can use is a good example of a systems understanding.