Polymer Film Farming

Because the polymer film holds on to water molecules, the plants on top have to work hard to absorb water and nutrients. The stress causes them to develop higher levels of sugars, amino acids and phytochemicals. In much the same way that growing wine grapes in poor soil produces concentrated fruit.

http://www.scmp.com/magazines/style/article/2094426/farming-without-soil-new-japanese-tech-makes-growing-fruit-and