CHLOROPLASTS AND MITOCHONDRIA IN THE LEAVES OF WHEAT AND RICE SEEDLINGS EXPOSED TO ANOXIA AND LONG-TERM DARKNESS - SOME CHARACTERISTICS OF ORGANELLE STATE

The seedlings of wheat (Triticum aestivum L.) and rice (Oryza sativa L .), which contrast in their tolerance to hypoxia, were used to study t he effect of anaerobiosis and long darkness on the content of pigments (chlorophylls a and b, carotenoids), ATP, proteins, the photochemical activity of isolated chloroplasts, and the succinate dehydrogenase (S DH) activity of mitochondria. Anoxia and darkness caused a similar des truction of pigments and proteins in the first true (physiologically o lder) leaves of wheat seedling,os. The pigments and proteins in rice s eedlings were more stable than those in wheat plants. After transferri ng plants from darkness and a nitrogen atmosphere to light and aeratio n, rice chloroplasts showed a complete recovery of photochemical activ ity, whereas wheat chloroplasts remained inactive, even after shorter treatments. The impairment of photochemical activity appeared earlier in Photosystem II than in Photosystem I, especially in intolerant whea t plants. In wheat seedlings, the ATP content and SDH activity decreas ed to such low levels after 48-h-long anaerobiosis that it was impossi ble to restore them after transferring the plants to aeration. In rice seedlings, the loss of ATP and reduction in SDH activity were slight, even after 72-h-long anoxia, and were restored rapidly with onset of aeration. These data lead to the conclusion that anoxia and prolonged darkness cause considerably less damage to chloroplasts and leaf mitoc hondria in rice seedlings than to these organelles in wheat.