Verbal description of the model of spatial organisation of gravitropic reaction

The difference of growth rates between opposite flanks of an axial organ is the cause of gravitropic curvature. In fact, such a specific definition is not necessary for imitational modelling. For modelling purposes, it is usually enough to assume that curvature just occurs in response to some signal. The factor (or factors) which code the delivery and intensity of this curvature in the modelling were considered to be "physiological signal" for tropic bending.

The basic scheme of the model was derived from those of Rawitscher (1932) and Merkys et al. (1972). The model assumes that during the gravitropic reaction the bending process is determined by the following factors (or signals):

bullet Gravitropic signal, perceived in the apex*and transmitted* to the bending subsection (realisation site).
bullet Gravitropic signal, perceived in the bending subsection*.
bullet Straightening, or compensation signal*, perceived in the realisation site. This signal is proportional to the local curvature of the bending subsection. This signal was introduced to explain the straightening of the apical part before reaching the vertical position.

The local bending speed in the subsection is determined by the sum* of these three signals. The gravitropic signals are positive, causing bending. The straightening signal is negative.

Such integration of signals in the hypothesis allows us to create a mathematical model, which is able to reproduce the real spatial organisation of the gravitropic reaction in the stem of the mushroom Coprinus cinereus.

NOTE * indicates hyperlink to mathematical description.

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