The smell of rain

To get right to the point, what the humidity in the air increases, it changes the vapor pressure of the atmosphere (locally anyway). Nitrates from the ground are then released and that is what you are smelling. An interesting thing is that the nitrates that are released will actually rise up and hit the underside of leaves on trees. When this occurs, many leaves will undergo a chemical reaction that will make the leaf actually twist so that it is upside down. Why do the leaves do this? It is a evolutionary process by which the trees get to wash the bugs off of the under side of their leaves! So, next time you can smell the rain, go and look at the trees, especially if there is a slight breeze, and you will see the leaves turn upside down!



#######################################


Why does grass smell only when it's being mowed?


According to botanists (plant scientists), the smell of cut grass is caused by gases emitted from each injured blade. Chopped grass releases a long list of volatile organic compounds, including methane (swamp gas), acetone (as in nail-polish remover), ethanol (grain alcohol) and acetaldehyde, a chemical similar to the toxic preservative formaldehyde.Plants produce the volatile compounds within seconds of being cut.

Some also produce the chemicals when they are damaged by frost.Botanists are still studying why wounded plants give off a burst of volatile organic compounds. One reason, they suspect, is that the chemicals have an anti-microbial action, protecting the cut part from invasion by microbes already teeming on the leaf surface.Some scientists suggest thinking of cut grass as a kind of chemical polluter. Volatile organic compounds from wounded grass react with nitrogen oxides in the air, helping to form more ozone near the ground (where we don't want it).


And grass sheared off and left drying on the lawn releases even more volatile organic compounds -- up to 10 times as much as the cut grass still rooted in the ground. So mowing the nation's lawns may be a significant source of air pollution, scientists say -- even trumping the pollution belched out by gas-powered mowers.

Still, most scientists say there's no reason not to enjoy the cut- grass smell on a summer day. When we bite and chew raw vegetables, they point out, the veggies release their own small burst of compounds -- just as grass, clover and other plants do when a hungry horse tears off a tasty mouthful

ps: i love the smell of cutting grass combine with the smell of rain......yess..kesan2 sampingan utk tunggu new project.. hahha