I have worked with the inventor of the Seawater Greenhouse for a number of years, so I thought I should help clear up some questions with how it works.
The greenhouse does not expose the plants to salt. So whilst it is interesting to understand how salt hampers the growth of plants it really doesn't have anything to do with how plants in a Seawater Greenhouse are grown. The water used in the greenhouse is distilled from seawater by internal processes in the greenhouse and the result is that the plants get distilled water, no salt at all.
The distillation process uses very little energy which you have to add to the process. You need a couple of kW to drive pumps and fans for each 1000 m2 greenhouse, the evaporative cooling effect using the seawater is the equivalent to using traditional refrigeration methods of 500 kW in this scenario. So the greenhouse is very energy efficient.
I hope that helps.
Thomas, http://www.greenocean.org/
