It is known that environmental stresses can have devastating effects on plants and represent the most limiting factors for productivity. Apart from biotic stress caused by plant pathogens, there are a number of abiotic stresses such as extremes in temperature, drought, salinity, heavy metals, radiation and mechanical wounding which have detrimental effects on plant growth and development. Certain plant species have developed various mechanisms to defence or adapt to such stress conditions.

Cyclic adenosine 3’:5’-monophosphate and cyclic guanosine 3’:5’-monophosphate, common- ly know as cAMP and cGMP, are key second messengers in living organisms ranging from bacteria to Homo sapiens. Cyclic AMP and cyclic GMP are produced from ATP and GTP by the action of adenylyl cyclase and guanylyl cylase and are hydrolyzed to AMP and GMP by the cyclic nucleotide phosphodie- sterase. The natural occurrence of cyclic nucleotides in higher plants is now established, as is the presence of enzymes involved in their metabolism.