Rice symbolizes, wealth and fertility.
Tossing rice, birdseed or confetti is used to wish the newly married couple a large harvest, abundance in life or many children.
Today many churches do not allow the throwing of these materials for safety or environmental reasons, as a result, a new tradition has emerged; blowing bubbles.
Although many see no harm in the bubbles, their are churches and reception facilities who do not allow this gesture as well. Please check to be sure beforehand.