Hi, my name's Dan Jenkins from Science and Plants for Schools.
I'm going to talk about
plant defences and
adaptations today and we've got a really
easy and interesting practical for your 
students to do
using the stinging nettle.
A stinging nettle
has got a fantastic adaptation. If you think
about how many times you have been stung
by them
it's just a brilliant one to use with your students. 
And we're going to get your students
look at the mechanism by which stings
work
For us we know that on the
underside of the leaves are
modified cells
which have needle-like projections which
contain formic acid
the very same acid that ant bites
cause irritation with
on your skin. 
It's a very simple investigation for them to look at.
All they need to do is to grab a stinging
nettle leaf. And you should be able to find
a stinging nettle some where in the school grounds.
They're everywhere.
You take a slice
of your stinging nettle leaf
on your slide
I'm wearing gloves to do this for obvious reasons.
and you put the lowermost
surface of the leaf facing you on the slide.
Take a piece of universal indicator 
paper
And you're going to dip that into tap water
just to moisten it, and then you lay it over
your stinging nettle and using a
piece of acetate
- OHP material - just cut to the size of your slide
you press that over the slide
pressing down on the universal indicator paper.
As you do that you'll be breaking those fragile stings.
and if you have a look at
the universial indicator paper and hold it up to the light
you'll see there are colour changes.
Little blotches of colour where the stings have burst.
and because it's acid we've got little yellow blotches there.
You can get your students to analyze whether the
stings are more prevalent on that higher leaves or on the lower leaves
We've got loads of other
investigations to do with plant adaptations
available on our website
If you go to www.saps.org.uk
We've got student sheets for this practical
We've got teacher notes on this and we've got technician sheets.
Go have a look, and see what you find.
