Saturday, 14 September 2013

The Guardians of Life...

Walking the dog through the fields the other morning at 0430 I looked up and saw a clear star filled sky. It then made me remember that my wife had called me a geek for arranging glow in the dark stars on the eldest daughter's ceiling according to the northern hemisphere constellation map!! That took me a while to do but I am proud to say that it has worked and her ceiling is now twinkling away each night!!

Anyway back to the walk...I picked a maize leaf because I wanted to photograph its stomata. Now these things are basically microscopic pores but like all those tiny things they play such an important part in ensuring the continuation of life on our planet.

Can you make out the small oval shapes in the photo below? These are the stomata.

Here is one in more detail. Given it was dark outside and when I took this photograph the stomata were closed.

Two cells called guard cells surround each stoma. These regulate opening and closing and control the exchange of gases between the leaf and the atmosphere.

Oxygen involved in respiration (getting energy to live) and carbon dioxide involved in photosynthesis (making food) enter through stomata. During the day you would normally see the stomata open letting in these two gases. The byproduct of photosynthesis is oxygen and this is released through the stomata to the outside world.

Water is also released through stomata via a process called transpiration. This is how water is able to travel freely through tiny seedlings to massive redwoods. 

So how does it work? Well without becoming too technical it is just the movement of water into and out of the guard cells. Water goes in and the guard cells become turgid and open, water goes out and the guard cells become flaccid and close. This is all controlled by the amount of light, carbon dioxide and a number of chemicals and hormones that the plant produces.

The classic study is to paint clear nail varnish onto a leaf's surface, peel it off and then view it with a microscope so keep a look out in the future for more posts.

So the next time you go out into the garden or look at a pot plant indoors, just give a thought to the the multitude of guard cells that are working non-stop to ensure your plants keep on growing. 

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