Putting philosophical issues and the definition of consciousness aside, plants can "make decisions" or anyway behave in a complex, context-dependent manner. This applies also for root growth patterns. For a neat example, see Shemesh et al (2010)
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0010824 and quite a few papers by Ariel Novoplansky. Asaf ________________________________ From: "Pekin, Burak K" <[email protected]> To: [email protected] Sent: Sat, May 21, 2011 6:30:09 PM Subject: Re: [ECOLOG-L] Communication Science to Public Plant Roots This seems to me more like a philosphical issue, rather than a scientific one. there are obviously several mechanisms that allow plants to actively "seek" water. However, unlike the mechanisms that allow an animal to seek water, such as detecting moisture in the wind using smell, they do not require a conscious desicion, i.e., the animal may decide to follow or not follow the scent, the plant does not have a choice. So the question is whether "seeking" requires a conscious desicion to be made by the individual. It could also be argued to what extent the desicions made by animals, such as humans, are conscious versus subconious and whether a subconcious desicion satisfies the definition of "seeking". -Burak Subject: Re: [ECOLOG-L] Communication Science to Public Plant Roots Well, I can't say what the narrator was basing his/her statement upon, but it can be justified. Roots are, for the most part, programmed to grow downward (positive geotropism), and in many if not most soil environments, water is more abundant at lower levels. Thus, growing downward means growing toward water. (One situation where this doesn't hold true is right after a rain, when the upper level of soil may be wetter then a lower level.) Additionally, roots (like all protoplasm-based structures) need water to grow. Thus, roots that are tentatively entering a wet zone (assuming it's not too wet) will grow faster than roots entering a dry zone, thus setting up a positive feed-back loop regulating root growth, which obviously has a genetic component. Finally, you may consider differential mortality of root cells in wet verus dry soil regions as also being a genetic program that causes the root SYSTEM to grow toward water. I think this is enough to justify the statement. Of course, the statement is a bit misleading in that it may call up the image of a little root tip sniffing first in one direction, and then in another, and finally saying, "Ah, the water's over there; I'd better grow in that direction." But this sort of imagery often colors our understanding of mechanistic processes in biology, even for scientists (for me, at least). Martin M. Meiss 2011/5/19 Wayne Tyson <[email protected]> > 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? > > WT
