Physiological and biochemical events

Kevers, C. Coumans, M.C. Coumans-Gilles, M.F. Caspw, T.H. (1984). Physiological and biochemical events leading to vitrification of plants cultured in vitro. Physiologia Plantarum, Vol.61, No.l, (May 1984), p>p. 69-74, ISSN 1399-3054... 

It is not our intention to present a detailed account of the morphological and anatomical aspects of seed development for this the reader is directed towards the relevant references in the bibliography [3, 14, 16]. It is necessary, nevertheless, to review briefly the developmental processes in the Gymnosperms and Angiosperms so that we can later set the physiological and biochemical events in their appropriate context. 

Pharmacodynamics is the study of dmg action primarily in terms of dmg stmcture, site of action, and the biochemical and physiological consequences of the dmg action. The availabiUty of a dmg at its site of action is deterrnined by several processes (Fig. 1), including absorption, metaboHsm, distribution, and excretion. These processes constitute the pharmacokinetic aspects of dmg action. The onset, intensity, and duration of dmg action are deterrnined by these factors as well as by the avadabihty of the dmg at its receptor site(s) and the events initiated by receptor activation (see Drug delivery). 

Null method, physiological or pharmacological effects are translations of biochemical events by the cell. The null method assumes that equal responses emanate from equal initial stimulation of the receptor therefore, when comparing equal responses, the complex translation is cancelled and statements about the receptor activity of agonists can be made. Relative potencies of agonists producing equal responses thus are interpreted to be measures of the relative receptor stimuli produced by the agonists at the receptor see Chapter 5.6.2. 

Ethylene coordinates the expression of genes responsible for enhanced respiratory metabolism, chlorophyll degradation, carotenoid synthesis, conversion of starch to sugars, increased activity of cell wall-degrading enzymes, aroma volatile production, and so on. All these events stimulate a series of biochemical, physiological, and structural changes making fruits mature and attractive to the consumer. 

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