Asaf, what the report says is that plants produce greater root growth in better environments than in poorer ones. There is nothing there that would cause one to conclude that plant roots that are in a poor environment will make a decision to find a better environment. The roots simply respond in a mechanistic manner to the different qualities of the environment. So, after an opportunity to grow, there are more roots in the better zone. How is this a "neat example" of the plant "making a decision"? mcneely
---- Asaf Sadeh <[email protected]> wrote: > 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 -- David McNeely
