Plants say "I need a drink"

When my wife looks at her plants, she can tell when they are a little thirsty.  So can I, but by the time I can tell they are nearly ready for the compost.  Suppose the plant could tell us when it needs a drink before it got in trouble.

A neat new technology has been developed to let plants tell us when they need water.  A small sensor clipped on a leaf reports it to a computer.  Orginally designed for space missions where 70% of astronauts time would otherwise be spent on maintaining their food plants, it has even more earthbound implications.
Wireless units are now being developed that have the potential to save fresh water.  A sensor on every 10-20 acres of crops could determine a crops water needs, reducing the water wasted on needless irrigation.  Since 70% of fresh water use goes to agriculture, the long term implications are tremendous.

The report with a 2 minute video is on Science Nation.

On another water front using technology to measure tree sapflow, there is interesting research on a tree's use of water from the National Science Foundation.
Some findings of their findings:

• shaded trees use less water
• trees in the wetland actually used less water because they tended to be smaller
• some trees actually used more water early or late in the day, and less during the middle of the day, possibly because they were not getting as much sunlight because they were in the shade of their taller neighbors.