[Effect of hypobaric hypoxia on the dehydrogenase activities of respiration and photosynthetic metabolism in barley seedlings].

Hypobaric hypoxia effects on enzymes of photosynthesis and respiration metabolism were explored in 8-day old seedlings of barley Hordeum vulgare L. in the dark or light. 16-hour exposure in rarified atmosphere that causes reductions of partial pressure of air gases and, consequently, hypobaric hypoxia (P(air) = 8.3 κPa, pO2 = 1.7 κPa, pCO2 = 0.003 κPa) up-regulated the activities of piruvate kinase, alcohol dehydrogenase, glucose-6-phosphate dehydrogenase and NADP x N-glyceraldehyde phosphate dehydrogenase both in the dark and light. NAD- and NAD-N-malate dehydrogenase activities were down-regulated. Levels of NAD- and NAD x H- malate dehydrogenases were decreased. Activation of the NADP-malic enzyme activity, invariably high activity of NADP-isocitrate dehydrogenase and growth of NADP x N- glyceraldehyde phosphate dehydrogenase are considered as a mechanism of barley seedlings adaptation to hypobaric hypoxia.