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Isolation-Inflicted Injury to Mitochondria from Fresh Pollen Gradually Overcome by an Active Strengthening during Germination

Department of Plant Physiology of the Agricultural University, Arboretumlaan 4, 6703 BD Wageningen, The Netherlands

Activities of segments of the electron transport pathway of mitochondria isolated from pollen of Typha latifolia L. during the course of germination in vitro were compared with those of mitochondria in intact grains. For this purpose, suitable inhibitors and artificial substrates were selected for their ability to penetrate through the exine, intine, and plasmalemma. In contrast to their counterparts in vivo, mitochondria isolated during the initial stages of germination exhibited low rates of electron transport, resulting from loss of NAD⁺ and displacement of cytochrome c from its site of action. The phosphorylative capacity was also impaired. Great caution must be exercised therefore, before interpreting results obtained with isolated mitochondria.

The gradually acquired resistance of mitochondria to injury during isolation as germination proceeds was shown to depend on an energy-requiring process and not solely on a rearrangement at the membrane level, or imbibitional differences. De novo syntheses of proteins or fatty acids were not required for the strengthening of mitochondria since cycloheximide, chloramphenicol, and cerulenin did not prevent this change. The nature of the energy-requiring process remains obscure. It is probable that strengthening of mitochondrial membranes during seed germination has been misinterpreted due to similar effects of isolational injury.

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