Circle of (Plant) Life

The plants around us provide a perfect hands-on biologyclassroom for students of all ages.  Fromplanting that first bean in a paper cup to conducting more involved andcomplicated high-school biology experiments, studying plants can be aneffective, concrete, fun, and low-cost way for students to explore the livingworld. 

Kids start learning about photosynthesis from a very youngage.  As toddlers begin exploring andplaying outside, their observations help them form ideas about plants and howthey grow.  By preschool age, manystudents have had the opportunity to plant seeds and water them to see themsprout.  They may find out that plantswill die when we forget to water them or when they don’t get enough sun.  As students’ experiences with plants increase,their perceptions of the way plants grow may change.  Often, by the time photosynthesis is formallyintroduced in the older grades, students already have some misconceptions aboutthe process.  If we can includephotosynthesis in science lessons from kindergarten on, learning the details ofthe process and understanding the chemical reactions involved will be mucheasier and more rewarding in middle school and high school.

Since plants are living things, it’s natural for students tocompare the functions of the plants to human functions.  Do plants eat, drink, and breathe likeus?  How are they different?  How are they the same?

One common misconception going into the study ofphotosynthesis is that that plants get food from outside sources such as waterand soil, much like humans get their food from outside.  All living things need to eat in order tohave enough energy to stay alive.  Plantsare the hard-working producers of the world, synthesizing their own food usingenergy from the sun.  They use carbondioxide and water with the sunlight to make their own food internally.

FT Exploring has a very easy to understand introduction to photosynthesis.  This resource describes photosynthesis in arecipe format and includes diagrams that simplify the concepts.  It answers the questions of how plants eat,drink, and breathe, and shows how these functions are different for plants thanfor humans.  Teachers could use this introductionfor a range of grades, going more in depth with the reactions for olderstudents and sticking to the more basic facts with younger students.  The following diagram is from their site.  

In order for a plant to carry out photosynthesis, water musttravel up into the plant from the roots. This is a fun phenomenon to explore, and would work well for primary orsecondary students.  You can introducesimple chromatography experiments with coffee filters and markers or allowstudents to place the stems of white carnations into water dyed with foodcoloring.   When bands of color travelout from a marker line or colored water travels to the tips of the carnationpetals, students will gain a visual understanding of how water can make its waythroughout a plant to take part in photosynthesis.  Take a look at one of our 2010 blog postsabout falllessons to see come neat chromatography ideas. 

Once students are on the right track with thebasic concepts of photosynthesis, their learning in the later grades will bemore successful.  If you have olderstudents and are ready to go more in-depth with the topic, be sure to look atthis comprehensive highschool unit.  This unit includesinquiry-based problem solving, hands-on photosynthesis demonstrations usingprops like tennis balls and balloons, and easy-to-follow procedures.  Another experiment that could go along withthat unit is Glucose Factory, where students experiment to see how much glucoseis actually inside different plant parts.

~Peggy's Corner - September 16, 2011~