The concept of interaction arises in the context of continuous functions. Verbally, it is the action of one independent variable on the action of another, and vice versa, on a dependent variable. Quantitatively, it is the second partial derivative of a function with respect to two independent variables. Misconceptions have arisen from attempts to understand action and interaction in discrete terms. The algebraic expressions for the actions of diuron and phorate on the fresh weight of oats and their interaction were determined from the regression polynomial and plotted in three-dimensional graphs. Three other mutually incompatible methods of assessing interaction, namely, the Colby (with its modification, regression estimate), the two-parameter, and the topographical methods were evaluated.
Dimethyl sulfoxide prevented loss of respiratory control and decrease in efficiency of oxidative phosphorylation when plant mitochondria were stored in liquid nitrogen. Respiration was severely inhibited and was not stimulated by adenosine diphosphate when mitochondria were frozen in liquid nitrogen without dimethyl sulfoxide. Thus, isolated mitochondria provide a model system for the study of the effects of freezing on biological membranes and of the prevention, by dimethyl sulfoxide, of freezing damage.
The usage of the word interaction by physiologists has led to a consensus that gibberellin and abscisin interact in affecting plant responses. However, no such consensus is admissible if one uses the statisticians' definition which is more physiologically sound than that used by physiologists.
The stability of isolated yeast mritochondria during refrigerated storage has been sttudied (9), but the comparable stability of m)iltochondria from a higher plant has not been reported. Preliminary experiments indicated that tom,a)to fruiit mitochondria were stable for at least 1 day after isolation anid showed a delayed response to the first addition of ADP whiile oxidizing succinate. Suich a dellayed responnse to the first addition of ADP with succinate as suibstratte h!as been reported for mitoch,ondria from seve,ral plant species and tissues (2, 6,9,13,14). Wiskich and Bonner (14) attributed this deliay to inihibitory amounts of oxa,loacetate, wrhile Verleur ( 13) attributed it to the quality of the mitochondria. In view of the conflicting interpretations of this delay, and th,e stability of tomato fru,iit mitocjhondria, a study of sucecinate oxidationi in these mitochondria was condtuted. This paper reporits effects dtue to storage and some of the factors controll1ing the delayed respon.se ito the first addition of ADP.
Materials and MethodsTomaito fruit (Lycopersi(cmn (sclienton7 AiMill.) were picked in the greenhouse or field the day of use. Mature green fruit were used except for table I which also includes data from tomato fruit vine-ripened in the greenhouse 5 d'ays past incipient coloring. The entire mitochonndrial isolation was done at 00 to 40. A sample of 62.5 g of outer perlicarp was rinised, chilled in crtushed ice, and then
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