Re: what type of effects could vinegar have on a plant watered with it?

Vinegar is very acidic.  Acids can have very negative effects
on living things.  Cells have an outer membrane made of lipids.  Although
plants also have a cell wall, they need the menbrane to survive.  In acidic
environments, the molecules that make up the cell membrane break apart,
causing damage to the cells.  Also, the H+ ion, what makes acids acidic,
is very small.  Because it is small, it can move right through the
membrane.  Once inside, it can continue to break up important molecules. 
It also causes problems because the protiens inside work best at the normal
pH inside the cell.  H+ decreases the pH, and thus stops some of the 
necessary reactions.
  A less direct problem would involve the soil.  Vinegar is acetic acid.
The acetate ion, the negative ion of acetic acid, makes many minerals more
soluble.  When watered, the vinegar, along with a lot of the minerals 
necessary for a plant to live,would come pouring out the bottom of the pot.

  It is still safe to put some vinegar on your food.  A few drops is 
ralatively harmless, and may actually help your body absorb minerals that
it dissolves from the food.  Just don't drink the vinegar.