What is the importance of a water potential gradient (in the uptake of water by plants)

Water moves from an area of higher water potential to an area of water potential. Having a water potential gradient will allow water to enter plant root cells through osmosis, otherwise, plant have to make use of active transport which requires usage of energy in the form of ATP. This increases the plants energy usage when such energy can be used for photosynthesis as well

In some developing nations the percentage of the animal protein from fish in the diet can be as high as 25 percent.  about 85% of fish caught is used for human consumption.  the remainder is converted into fishmeal and fish oil.