MadSci Network: Botany

Re: how can i do an experiment that show plant tropisms and growth hormones

Date: Mon Apr 21 19:10:40 2003
Posted By: David Hershey, Faculty, Botany, NA
Area of science: Botany
ID: 1050905881.Bt

If you want a project that deals with both plant hormones and plant tropisms, 
that narrows your choices severely. You have a lot more choices if you just 
focus on plant hormones or just on plant tropisms. 

One of the few projects you could do would be some of the early phototropism 
experiments with grass seedling coleoptiles. These experiments by Charles 
Darwin, Fritz Went, Boyson-Jensen and others are described in college Botany 
and Plant Physiology textbooks. They are simple experiments but require some 
precision because they deal with small seedlings.

One of the main phototropism-hormone experiments was to cut off the coleoptile 
tip and place it on agar, allowing hormones to diffuse into the agar. The agar 
was cut into a small block and placed back on one half of the cut tip of the 
coleoptile to see of the hormone could induce bending. You could also try 
adding different hormones to the agar or different amounts of auxin.  

Other types of coleoptile phototropism experiment are 
1. use mica plates to block hormone diffusion down one side of the coleoptile 
or laterally from one half of the coleoptile to another
2. use foil caps to block light to coleoptile tip
3. use different colors of light to determine which color(s) activate 

You can cheaply and simply estimate the concentration of auxin you collect in 
agar blocks using a bioassay such as the Avena coleoptile curvature test. 


Phototropism experiments

Phototropism Part I: Light and auxin

Went's Avena Coleoptile Curvature Test

Plant Hormones - Auxin

The Avena Test - a Bioassay

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