Abstract. Auxins (IAA, NAA, p-CPA) caused 20-30% promotion of respiration of auxin-dependent cell cultures of Nicotiana tabacum, Glycine max, Taraxacum mongolica, and Atriplex sp. and had small if any effect on respiration of auxin-independent cell cultures of Rubus sp. and Scorzonera hispanica. Antiauxin (p-CPIBA) did not affect the respiration. The auxin effect on the respiration of tobacco cells was revealed 10 min after its addition to the suspension and reached a maximum value in 60 rain. This stimulation preceded the induction of cell division by auxin. Mitochondria isolated from auxin-treated tobacco cells had greater oxidative and phosphorylative activity than mitochondria from untreated cells. However, isolated mitochondria did not respond to auxin. The inhibitors of respiration (cyanide, monoiodoacetate, malonate, and 2,4-dinitrophenol) eliminated auxin effect on the respiration and cell division. It is concluded that the promotion of respiration is a common event for the auxin effects both on cell extension and on cell division. This promotion is necessary for the induction of cell division and is exerted via direct activation of mitochondria in situ.Auxins not only stimulate cell extension but also induce cell division, especially in isolated culture. The stimulation of cell extension is usually accompanied by the promotion of respiration (Audus 1960, Bonner andBandurski 1952). However, it is uncertain if respiration is promoted when auxins induce cell division.Normal (nontumorous) plant cells cultured in suspension are the most suitable objects to elucidate this problem, because their division has an obligatory dependence on exogenous auxin. Many authors have reported that initiation and growth of callus and cell cultures in the media with auxins was accom-
Cold shock (-4° C, 1 h) induces qualitative and quantitative changes in the composition of free fatty acids in mitochondria of winter-hardy cereals (Secale cereale L.,Triticum aestivum L.). The amount of these compounds and the degree of their unsaturation increases. Simultaneously, a marked change occurs in the oxidative and phophorylative activities of the mitochondria: respiratory control decreases, respiration in state 4 and antimycin A-resistant respiration increase. The changes in mitochondrial activity are presumed to be caused by endogenous free fatty acids, the amount of which is increased because of phospholipase activity.
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