Translocation physiological basis

In this review I address the phloem mobility of agrichemicals from the viewpoint of a phloem physiologist. First, I will present an overview of the physiological basis of translocation by using... 

Under basal conditions, PKC is predominantly a cytoplasmic protein. Upon activation by Ca2+ or DAG, the enzyme associates with the plasma membrane, the site of many of its known physiological substrates, including receptors and ion channels. In fact, the translocation of PKC from the cytoplasm to the membrane has long been used as an experimental measure of enzyme activation. Such translocation has often been assayed by phorbol ester binding phorbol esters are tumor-promoting agents that selectively bind to and activate PKC. The molecular basis of the translocation of PKC from the cytoplasm to the plasma membrane has been solved. Subsequent to activation, PKC binds with high affinity to a series of membrane-associated proteins, termed receptors for... 

Professor Filhr discussed penetration, translocation and distribution of fungicides in plants. These aspects of fungicide performance are often critical in determining the success of a systemic fungicide in a particular type of application. The ability to penetrate into plant tissue and move while retaining activity therein is the primary basis for the superiority of the newer systemic fungicides over the older surface protectants. Internal therapeu-tants may also influence the host physiology and as a consequence, be assisted by the natural defense system of the host. 

On the basis of these differences it is reasonable to expect differences in physiological and biological action. Indeed, the members of the group show a wide variability in the mode of uptake (root, stem, leaf), the measure and rate of absorption and translocation, and their distribution and metabolism within the plant. All of these differences indicate that in spite of their chemical relationship, the biological mode of action of the individual active substances is different, as well as the detoxication mechanism of the herbicides in the plants of different sensitivity, the latter phenomenon being responsible for their selectivity. 

The visible symptom of the herbicidal action of difenzoquat, withering of leaves, develops slowly, often in 3-4 weeks. However, the growth of wild oat is quickly halted, and often swelling, yellowing and necrosis can be observed in the basal stem area, indicating the translocation of the herbicide into the meristem. On the basis of the physiological symptoms observed, difenzoquat is primarily a mitosis poison, but it also affects other vital processes in wild oat. 

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