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Transpiration in Plants

Bob Vickery vickery at mpx.com.au
Sun Mar 10 00:00:55 EST 1996

In article <31381D0F.5568 at ibl.bm>,
Roderick Ferguson <rafergus at ibl.bm> wrote:

>Experiment Investigating the Effects of Surface Area and Wind Speed on 
>the Rate of Transpiration
>I have come to the following conclusions in my investigation and I would 
>appreciate if someone would e-mail me, to confirm my conclusions:
>1.  Surface Area is proportional to the rate of transpiration due to the 
>direct effect which it has on evaporation, and therefore the rate at 
>which the water escapes from the stomatal air spaces of the leaves of 
>the plant.
This is right if you compare rates of transpiration of different numbers of
leaves of the same species.  When you compare little leaves with big
leaves, the little ones lose more water per unit area than big ones because
the wind is more efficient at sweeping water vapour away from little ones.

>2.  Wind Speed is also proportional to the rate of transpiration between 
>no air movement and a low wind speed such as 2.5 mph.  However, it 
>begins to reach a limit, and curves to become a logarithmic graph, as it 
>rapidly reaches it's maximum effect and therefore maximum rate.  This is 
>due to the wind speed increasing the speed at which water vapour is 
>moved away from the air around the leaf.  At a certain wind speed, the 
>water molecules are moved away from the plant at such a speed that the 
>air surrounding the stomatal air spaces always has a  humidity of 0%, 
>and therefore the wind speed has reached it's maximum effect.  I think 
>that this must be due to a limiting factor.  Could it possibly be 
>surface area?
A physiologist would say that the limiting factor is the rate at which the
water gets through the stomates, but since the number of stomates is
proportional to the area (of a given leaf), your statement is correct.
>I would really appreciate a response.  Thank you very much
>Roderick Ferguson,

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