[Reorganization of the chloroplast thylakoid system during decay of acquired thermotolerance of photosynthesis and aging of wheat leaves].

A 3 hours heating at 39 degrees C of 14-day old wheat plants increases the termotolerance of photosynthesis, and also the length and number of thylakoids in chloroplast in mature leaves. The acquired termotolerance disappears within 10 days. Simultaneously the intensity of photosynthesis and the length of thylakoids decrease.

[The cellular reaction to heat shock: the physiological aspect].

This review regards the basic manifestations of cell response to heat-shock (HS): formation of resistance increase or acquired tolerance, and contribution of stress proteins (SP) to this reaction. This to great extent nonspecific increase in heat-shock cell resistance is based on two processes: a) an increase in the initial heat resistance of cell functions which results from enhancing of resistance of native efficient state of cell protein macromolecules to denaturating agents; b) stimulation of cell repair capacity that is expressed as an increase in the rate of cell function restoration in the case of its equal extent of damage in trained and untrained cells, and as expansion of the repairable zone (the interval of temperatures within the limits of which the function is inhibited completely, but reversibly after certain duration of heating). Stimulation of cell repair capacity is due to a more rapid renativation or substitution of proteins modified by stress.