Chemistry Reference
In-Depth Information
Darwin expressed that “
Roots are as brain of plants
" [34], i.e. roots can be taken as a
similar body like the brain. Currently, it is known that for the transmission signals (changes
of potential) between root and above-ground plant parts plasmodesma are needed and there
seems to be an important role for auxin molecule (IAA). For example, information about
pathogen attack or strong physical stress can be quickly transmitted from the roots to the
other plant parts in order to begin start as soon as possible organism defense thanks to
plasmodesma. The genes for some plasmodesma proteins that form the connections are
similar to the neuron proteins. The root system has the role as control centre with rapid
transmission information to other plant parts. New situation creates a certain type of
synapses, which are to some extent „the plants memory“, i.e. certain type of reaction to
already known situation. If the stress is repeated again, the reaction of the plant is more
rapid on the basis of this memory [2, 4, 6, 7, 8, 9, 10, 11, 30, 56, 69, 80, 82, 83, 87, 91]. It is also
known that root apices during growth can recognize in advance dangerous soil substrate
and avoid them using similar active avoidance root tropism.
Biochemical pathways - root influence of the shoot
Last, but not least, there are significant advances in ecological studies, behavioral studies, on
memory and learning phenomena in plants.
Baluška in his work gives a very detailed
interpretation (verbatim quotation)
[6]. “
The plant neurobiological perspective reveals several
surprises when the classical plant hormones like auxin, abscisic acid, ethylene, and salicylic acid are
considered from this angle. Auxin and abscisic acid elicit immediate electric responses if applied to
plant cells from outside, suggesting that their regulated release within plant tissues may be a part of
neurotransmitter-like cell-to-cell communication. Abscisic acid signaling pathway is conserved
between plants and animals and this signalling molecule both stimulates and is endogenously
produced in human granulocytes in a way suggesting that it acts as endogenous proinflammatory
cytokine. Biologically active abscisic acid was isolated also from brains of vertebrates indicating
possible roles of abscisic acid in the central nervous system. Salicylic acid activates similar subset of
MAPKs as voltage pulses. Ethylene, a classical plant hormonone, is an anaesthetic, a fact that plant
physiologists have ignored until now. Interestingly, anaesthetics used on animals including man,
induce anaesthetising effects on roots similar to those of ethylene. Ethylene is released in mechanically
stressed plant tissues, and structurally diverse anaesthetics activate mechanosensitive channels. As
ethylene is released after wounding, it might act to relieve 'pain' in plants. There are numerous other
plant-derived substances, which manipulate the pain receptors in animals, such as capsaicin,
menthol, camphor. Interestingly, the monoterpene volatiles, menthol and camphor induce oxidative
stress and inhibit root growth in maize, indicating that they, too, act as plant signalling molecules.
Finally, plants express inhibitors that are specific to the neuronal nitric oxide synthases. Another
example of neuronal-like behaviour of plants is the report that prevention of nyctinastic movements of
leguminous leaves causes their death while leaves allowed to 'sleep' stayed healthy. This resembles the
situation in animals. Although melatonin was discovered in plants more than ten years ago, we know
almost nothing about roles of melatonin in plants despite the fact that it is biochemically closely
related to auxin. Interestingly in this respect, melatonin mimics auxin in the induction of lateral root
primordia from pericycle cells.”
