Nutriceuticals Workshop MODERN CONCEPTS IN BIOLOGY OF WHAT A PLANT IS by Florianne Koechlin Biologist, Blueridge-Institute, Basel - Switzerland www.blueridge-institute.ch www.blauen-institut.ch 1. Plants communicate A tomatoe-plant, when attacked by caterpillars, starts defending itself (eg production of toxins against invaders ) The plant also releases odours to warn neighboring plants so they start their self-defense. The odour is known to be a mixture of methyl- jasmonates (also used in perfumes). Triangle maize – caterpillar parasitic whasp : Experiments by Ted Turlings, University Neuchatel (CH) show that when maize is attacked by caterpillars, little whasps (Spdoptera Exigua Hübner) arrive soon and parasite the caterpillar. The plant sends out „SOS-signals“ to attract the whasps. The plant „tastes“ the presence of caterpillar by a molecule (volicitin) in their saliva and then starts to produce the SOS-signal – a flexible triangle. (T.Turlings and B.Benrey, 1998, Ecoscience, 5 (3), 321) „Communication“ among plants with the help of scent-molecules is common („a constant chattering“) 2. Plants react to at least 16 parameters from the environment. Plants can sense light, temperature, gravitiy, movement, chemicals etc. They react to these parameters, change their behaviour accordingly (such as growth, number of leaves, thickness of stem). 3. Plants „learn“ through trial and error The overall goal is to maximise fitness in an unpredictable, ever changing and extremely complex environment. Example: Rootsystems must make decisions about growth, direction, dephts, avoiding competing roots etc. They must integrate signals of soil hardness , stones, light penetration, temperature, insects and microbes, distribution of water, Calcium and niotrate, presence of gases such as CO2 etc; they compute these signals together with many internal ones into decisions which are necessary for root-growth. (A.Trewavas, 2004, Annals of Botany 93, 353) 4. Plants have a “memory“ Animal memory is often defined as: The experience of one organ can be used to the advantage of others. Such processes are also known for plants. Example: The pre-exposure of roots of a growing plant to low levels of salt or to dryness enables the plant to survive later in normally lethal concentrations of salt or in draught. The experience of the roots is thus translated to the whole plant. Pre- treatment learning can last months or years, it also can be interrupted if the conditions are reversed. (A.Trewavas, 2004, Annals of Botany 93, 353) 5. Are plants „intelligent“? Anthony Trewavas (University Edinburg, GB) thinks so: Among the many definitions for „intelligence“ he chooses the one given by David Stenhouse (philosopher and psychologist from New Zealand): „adaptive and flexible behaviour during the lifetime of an individual“. This is what plants are doing: they show a flexible, adaptive – and most important: not all-predetermined – behaviour (although their behaviour changes might be small and slow) Example: Cuscuta, a parasitic plant which sucks the juice of its hosts: Cuscuta comes to a hostplant and checks first, if it is worthwhile. If not: it moves on., If yes: it starts building coils around the host. Cuscuta also computes if the host is a good one or not: Many coils around a good one, few coils around a meager one. Amazing fact: from the first encounter to the point where Cuscuta gets to juice and nutrients from the host there is a timelaps of 4 days. Cuscuta computes the outcome 4 days in advance and reacts accordingly. This, Trewavas concludes, is intelligent behaviour. Studies show, that the molecular basis of learning in animals and in plants is very similar (eg equal or similar signal pathways ) But where is the brain? Probably it is the whole plant, probably the membranes of cellplasma, where hundreds of signal-molecules are located . It’s probably there where most of the interactions and computing is done. 6. Differences between plants and animals Animals move, plants are sessile. Plants show an open organisation, a modular growth; they are „meta-populations“ Each organ is quite independent of the others. You can cut branches from a tree, you cannot cut legs from an animal. Development and growth of animals means development of an individual. Development and growth of plants means adding new members (eg leaves, roots), getting rid of others. Plants consist of ever changing components. Both plants and animals show much flexibility to optimise their fitness. And Trewavas adds: „Intelligence“ in our culture is always defined in relation to action: Animals must be fast, flee or attack. But plants do not move fast, they donot appear to be clever. Their flexible behaviour may show within hours or days. 7. Conclusions Not: Stop eating salade....But perhaps this radical new scientific view of what a plant is might help change our perception of plants, might help argue against transgenic plants, terminator and patents on plants. It also opens new and exciting perspectives for agriculture (eg use of odours, enhancing induced self-resistence etc) Article 24 of the Swiss constitution prescribes that the „dignity of creature“ has to be guarded. Are plants creatures? If Yes, what are the implications? The Swiss Ethics Committee EKAH (of which I’m a member) will discuss this issue in near future.
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