Electrolyte leakage accompanies plant response to stresses, such as salinity, pathogen attack, drought, heavy metals, hyperthermia, and hypothermia; however, the mechanism and physiological role of this phenomenon have only recently been clarified. Accumulating evidence shows that electrolyte leakage is mainly related to K + efflux from plant cells, which is mediated by plasma membrane cation conductances. Recent studies have demonstrated that these conductances include components with different kinetics of activation and cation selectivity. Most probably they are encoded by GORK, SKOR, and annexin genes. Hypothetically, cyclic nucleotide-gated channels and ionotropic glutamate receptors can also be involved. The stress-induced electrolyte leakage is usually accompanied by accumulation of reactive oxygen species (ROS) and often results in programmed cell death (PCD). Recent data strongly suggest that these reactions are linked to each other. ROS have been shown to activate GORK, SKOR, and annexins. ROSactivated K + efflux through GORK channels results in dramatic K + loss from plant cells, which stimulates proteases and endonucleases, and promotes PCD. This mechanism is likely to trigger plant PCD under severe stress. However, in moderate stress conditions, K + efflux could play an essential role as a ‘metabolic switch’ in anabolic reactions, stimulating catabolic processes and saving ‘metabolic’ energy for adaptation and repair needs.

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Stress-induced electrolyte leakage: the role of K+-permeable channels and involvement in programmed cell death and metabolic adjustment

Cellular death and necrosis: chemical, physical and morphologic changes in rat liver.

Mechanisms and physiological roles of K+ efflux from root cells.

Spectrochemical Analysis of Vegetative Cells and Spores of Bacteria

A good deal of attention has been paid to the temperature coefficients of vital processes. The data available up to 1914-15 are for the most part collected in Kanitz' (1915) book. The chief interest of this work has centered about the \"R. G. T.\" (van't Hoff) rule. In common with many chemical reactions, at ordinary temperatures the velocities of a variety of protoplasmic activities are found to be about doubled or trebled by a 10 ° rise of temperature. The temperature coefficient, Q,0, giving the ratio of velocities for an interval of 10 °, is a quite imperfect means of characterizing a process. I t is in any case not a constant quantity, but depends upon the particular temperature. Moreover, it is known that in the neighborhood of certain temperatures, varying with the process considered, abrupt changes occur in the temperature relations of many biological phenomena. A means is required of dealing with these \"critical points.\" Such complexity of dynamical balance as must be postulated for living matter leads one to expect that by considerable change of temperature a different fundamental reaction might be brought into control of the velocity of a given phenomena. For certain vital activities which may be taken as typical,, it is found that the underlying or controlling processes may be treated as systems of \"irreversible\" first order reactions (Osterhout, 1914, 1922; Hecht, 1918-19, 1918-19, a; Osterhout and Haas, 1918-19).

https://rupress.org/jgp/article-pdf/7/1/123/1247046/123.pdf

C. A. Kofoid

Papers

Injury, Recovery, and Death, in Relation to Conductivity and Permeability