Essay: Student alternative conceptions in secondary level plant science

After much deliberation, I’ve decided to put this online. Here’s the first essay I wrote during teacher training. Monash University was kind enough to award it the top grade 🙂 


A plant, according to the Oxford English Dictionary, is “a living organism of the kind exemplified by trees, shrubs, herbs, grasses, ferns, and mosses, typically growing in a permanent site, absorbing water and inorganic substances through its roots, and synthesizing nutrients in its leaves by photosynthesis using the green pigment chlorophyll.” (Oxford English dictionary online, 2013). The study of plants is so fundamental to a child’s education that the Victorian Essential Learning Standards (AusVELS) contains elements of plant science as part of the Australian Curriculum at every level from Foundation to Year 12 (Victorian Curriculum and Assessment Authority, 2013). The study of plants is necessary to equip students with an elementary understanding of their natural environment. Furthermore, plant sciences at secondary level can cultivate in them a passion for plant sciences at university, which provides the basis for careers in agricultural research, drug discovery, ecological management and carbon sequestration—industries that are enjoying booming interest worldwide for both moral and financial reasons.

There exist a variety of alternative conceptions (ACs) about plants among secondary school students. ACs are constructed from the students’ own experiences, from conversations (with adults and other children) and from the media (advertisements and cartoons). Chiappetta & Koballa noted that ACs, once constructed, are “tenacious and resistant to extinction by conventional teaching strategies” (Chiappetta & Koballa Jr., 2006). Students can only learn when they “delete their pre-existing misconceptions” and accept what is being taught (British Educational Communications and Technology agency [Becta], 2001). However, changes to these preconceived notions are difficult to materialise, and can only be achieved through exceptionally high-quality teaching practices. Teachers must not only construct knowledge (i.e. teach), but ‘deconstruct and reconstruct’ the students’ existing knowledge (Layton, 1991) by facilitating respectful experimentation of ideas (Brooks & Brooks, 1995). Inadequate teaching methods will result in many students rejecting the new information presented (Becta, 2001). This paper analyses four ACs related to plant science, each of which is a direct contradiction to the meaning of ‘plants’ as defined previously.

First, students have most difficulty understanding the fact that plants obtain 100% of their growth material from atmospheric CO2, and instead hold the AC that plants somehow extract “food” from the soil (Weld, 2004). This AC arises from children’s constructed knowledge (from years of eating experience) that “food” is usually solid, is sometimes liquid, and is never a gas, and that air has always been “inedible”. The fact that “plant food” (available in gardening stores) should be placed on the soil surface and not on the leaves would add weight to their constructed AC even further. Demonstration of hydroponics (by video), emphasis on how most plants ‘do not eat’, and referring to store-bought ‘plant food’ as ‘plant minerals’ may help students to re-construct their ideas.

Second, a significant number of students have difficulty understanding how plants absorb water through the roots, and instead hold the AC that leaves absorb (or even attract) rain and other sources of falling water (e.g. from a watering can). When watering plants, most of the water (accidentally) falls on the leaves, which may, over time, give children the impression that occasionally wetting the leaves is crucial to a plant’s survival. Direct evidence of plant transpiration is seldom obvious in daily life, which allows their AC to flourish without refutation. To remedy this, an interactive classroom experiment conducted over two to four weeks can demonstrate that roots need watering, and that leaves do not. A second experiment can demonstrate that leaves are waterproof and do not absorb water when wet.

Third, some students have difficulty grasping the breadth of the definition of ‘plants’, and reject the idea that this category includes mosses, grasses, algae and trees (Bianchi, 2000). This AC is incongruent with the accepted, scientific definition of ‘plant’ (meaning Plantae; even the strictest definition of Plantae includes all land plants and the only common exclusion is ‘algae’), and may have arisen from a shortening of the word ‘house-plant’ or ‘pot-plant’ in normal conversation (Oxford English dictionary online, 2013). Teachers can help students challenge their pre-constructed definition of ‘plants’ by using PEEL practices B3, ‘guided discussion’, and A3, ‘What’s my rule?’ (Mitchell, 2007).

Finally, some students do not see plants as ‘living’, but instead see them as inanimate objects that should not be studied in biology (Weld, 2004). This AC is constructed as a result of plants moving imperceptibly slowly, and from early childhood perceptions of what is ‘alive’ (i.e. people and animals, which share many common features with people). Time-lapse videos of plant growth found in nature documentaries are powerfully persuasive tools, which demonstrate ways in which plants react dynamically to their environment. Teachers can reconstruct this AC by demonstrating plants’ responsiveness to light, touch, gravity, water and nutrient availability using live specimens and online video resources.

Alternative conceptions left unresolved by inadequate secondary-level teaching practices could have wide-ranging, long-term negative effects on society. Given the current state of escalating food prices, runaway ecological degradation, and the social stability threats posed by anthropogenic climate change, a correct understanding of plants at the secondary level is imperative not only for these students and their families, but also for the future of humanity as a whole. ■

862 words



Bianchi, Lynne. (2000). So What Do YOU Think a Plant Is? Primary Science Review 61:15–17

British Educational Communications and Technology agency (Becta) (2001). The importance of activities in the teaching of science: a constructivist perspective on teaching science. Retrieved from (24/1/2001)

Brooks, M. & Brooks, J. (1995). In Search of Understanding: The Case for Constructivist Classrooms, Alexandria, VA, USA: ASCD.

Chiappetta, E. L., & Koballa Jr., T. R. (2006). Science Instruction in the Middle and Secondary Schools. Developing Fundamental Knowledge and Skills for Teaching; 6th ed., Columbus, OH: Pearson Merrill Prentice Hall.

Layton, D. (1991). Science education and praxis: the relationship of school science to practical action. Studies in Science Education, 19, pp. 43–79.

Mitchell, I. J. (2007). Teaching for Effective Learning: The complete book of PEEL teaching procedures, Melbourne, VIC: PEEL Pub.

Plants. Def. 1. (2013). In Oxford English dictionary online. Retrieved from (10/3/2013)

Victorian Curriculum and Assessment Authority. (2013). AusVELS and the Australian Curriculum. Retrieved from (11/03/2013)

Weld, J. (2004). The Game of Science Education. Boston: Pearson.

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