---- Wayne Tyson <[email protected]> wrote: > Ecolog: > > I just surfed across a "science" program on the "History" channel. The > narrator said "Plant roots are genetically programmed to seek water . . ." > > Will someone please inform me of the basis for this statement?
Wayne, misunderstanding is the sole basis of the statement. Since plant roots fail to grow in dry soil, but do grow in soil of the proper moisture content for that plant species, lots of folks get the idea that they "seek" water. The error has been repeated ad nauseum, including in some elementary biology texts, where the authors should know better. Even simple experiments seem to support the idea for people ignorant of the mechanisms involved, since if a plant is offered a divided environment, one part dry, the other part moist, after a while there will be roots in the moist soil, but not in the dry. But the significant point here is that the roots can only grow in the environment where they occur, not "seek" an environment they do not occur in. Some desert trees have very long roots that reach deep into the soil. When I was growing up in west Texas it was commonly held belief that mesquite trees "seek" the water table. Of course, they do not. They grow in soil sufficiently moist for their roots, and that is why in deep desert, they occur only in the more moist locations like riparian areas. mcneely mcneely
