ABSTRACT
At the cellular level, the signaling with compounds earlier known as neurotransmitters (acetylcholine, dopamine, noradrenaline, adrenaline, serotonin, and histamine) in various contacts between plants and other living organisms in plants may be analyzed as (1) signaling outside the cell (intercellular signaling with the compounds and enzymes of their metabolism) and excreted by any cell—from plant cell of the same plant individual or other plant species contacted with animal or/and microorganisms and (2) intracellular signaling (within plant cell) including transfer of external signal by secondary messengers, contractile, vesicular systems, or direct influence of intracellular neurotransmitters as intracellular regulators on the organelles.
