Re: density of stomata and the effect this has on transpiration

It is not a simple relationship between stomatal density and transpiration rate 
because there are many other leaf and environmental factors affecting 
transpiration. Other leaf factors include how open the stomata are, maximum size 
of stomatal opening, if stomata are sunken or not, leaf hairness, leaf 
orientation, which side(s) of the leaf stomata are on, and leaf area per unit 
ground area (Leaf Area Index). Environmental factors include light level, wind 
speed, relative humidity, soil water content and temperature. Stomatal density 
can also be affected by the environmental conditions under which the leaf 
develops.

Meyer et al. (1973) has a table of stomatal densities for 39 species. Stomatal 
density ranges from 1,400 per square cm for wandering jew (Zebrina pendula) to 
103,800 per square cm for scarlet oak (Quercus coccinea). Both measurements were 
for lower leaf epidermis.

It is fairly easy to measure stomatal density using a microscope and leaf 
surface impressions made with fingernail polish painted on the leaf and allowed 
to dry. Lift the dried fingernail polish with a piece of transparent tape and 
stick it to a microscope slide (Hershey 1995).

References

Hershey, D.R. 1995. Plant Biology Science Projects. New York: Wiley.

Meyer, B.S., Anderson, D.B., Bohning, R.H. and Fratianne, D.G. 1973. 
Introduction to Plant Physiology. New York: D. Van Nostrand.