Abscisic acid (ABA) is a biologically active substance that takes part in the various biochemical and physiological processes in the plants. There is currently limited knowledge about how these biochemical and physiological processes are triggered and regulated by ABA. Dozens of receptors have been described for ABA signaling but there is no any information why does ABA have so many receptors and how they act at the molecular levels. In this connection I would like to stress that not all cell proteins conjugated with ABA necessarily can be represented as hormone-receptors complexes. In this paper I proposed that physiological processes in plants are performed at molecular level by elementary chemical reactions (redox reactions) that trigger the cascade of subsequent reactions and that can be caused by various chemical and physical factors. Gene keys (fragments of polynucleotides, non-protein receptors) and gene locks (start fragment of genes) are also described. Keywords: abscisic acid, free radicals, receptors, gene keys, gene locks.

The characteristic chemical fragments named as functional reactive groups (or descriptors) in the molecules of biologically active substances (BASs) are described. These fragments are characterized by the presence of an active hydrogen atom or unsaturated function. It is concluded that BASs are essential factors working in concert with gene keys and gene locks to starts transcription. The gene keys are nucleic acids but not proteins. It is postulated that cell membrane can serve as depot for gene keys at the beginning of oxidative stress. During the recession phase of oxidative stress new gene keys are synthesized for new transcription acts. Keywords: BASs, descriptors, gene keys, gene locks, transcription.

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