The Physiology of Plant Integrity

The original concept of the plant integration system is presented and exemplified by the data from the studies of the regulatory controls that mediate the effects of red light (R) on the growth of etiolated maize seedlings. The integrity of higher-plant behavior depends on the functional activity and interaction of the dominant (control center). In vegetating plants as the simplest case, these centers include the shoot apex and the distal part of the root comprising the sensory tissues, the zones of the synthesis of specific hormones, and the zones of high morphogenetic and sink capacities. The system of propagating electric signals is usually devoid of the permanent generation centers. The dominant centers recognize the external and internal signals and induce the development of polarity (the bioelectric and physiological gradients), canalized connections (the conducting bundles), and oscillations. Trophic, hormonal, and electrophysiological signals of intercellular regulation are propagated along the conducting bundles and affect the intracellular membrane, metabolic, and genic control systems. The regulatory controls comprise the receptor cells recognizing the external and internal signals, the tissues of connection channels, the effector cells, and the feedback loop elements. When three-day-old etiolated maize (Zea maysL.) seedlings are treated with red light (RL), the photosignal is recognized by the phytochrome in the cells of the mesocotyl intercalary meristem; as a result, the positive biopotential is prolonged in these cells and in the coleoptilar node. An electric field (the receptor potential) thus produced would hamper, by electroosmosis, IAA transport from the coleoptile into the mesocotyl and in this way, would drastically inhibit the growth of the latter and temporarily promote the growth of the former. The primary leaves, also recognize R, as a result R promotes cell growth and the synthesis of gibberellins. The Ukhtomskii's principle of the dominant is used to interpret the plant ability for switching over its physiological systems in response to specific signals.