RESPIRATION AND MORPHOLOGY OF MITOCHONDRIA IN THE CROWNS OF WINTER-WHEAT PLANTS EXPOSED TO LOW-TEMPERATURES AND CARTOLIN

The respiration and ultrastructure of mitochondria from winter wheat ( Triticum aestivum L.) crowns were studied with emphasis on the adaptat ion of plants to low temperatures during the autumn-winter period unde r field conditions. Analysis of the separate and combined oxidation of substrates revealed competitive relations between succinate dehydroge nase and malate dehydrogenase-the mutual inhibition of these enzymes. Succinate was the preferable substrate of oxidation compared to malate during autumnal months, but the predominance of succinate oxidation d iminished during cold hardening. During cold hardening, mitochondria c hange their shape, e.g., their cross-sections acquired toroidal, dumbb ell-shaped, and other unusual profiles. Presowing treatment of seeds w ith the growth regulator cartolin raised the morphological heterogenei ty of mitochondria, caused their association into reticular structures , induced the ''succinate-type'' of respiration, and elevated the tate of cyanide-resistant electron flow. All this indicates intense energy metabolism, which promotes metabolic adaptation. Freezing temperature s induced the ''disintegration'' of complex mitochondrial profiles, de generation of cristae, clarification of the mitochondrial matrix, and depression of the oxidation rate. At the same time, freezing temperatu res led to an increase in the plasmalemma area at the expense of numer ous foldings and invaginations, and the induction of endocytosis. It i s concluded that compensatory rearrangements of mitochondria and plasm alemma during cell adaptation to low temperatures depend on the degree and duration of cooling.