S on keywords

Someone once told me that If I use a word and it has a S on the end then I would not have to use it twice my keywords, for example

air plants - google would also use it as air plant
air plant - google would not list air plants

Sorry if I am not making myself clear, I very rarely do. But does the above sound right to you?

Thx Kruger

it is not working that way in google at this time, it sees them as separate words, not the plural of the keyword.

if its for your body text use both
if its for your keyword meta tag use "air plants plant"