Cold Storage of Isolated Class C Chloroplasts

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Abstract
Preservation of photosynthetic activities (photophosphorylation, electron transport, fluorescence induction and 0.3 s delayed light emission) of isolated broken (class C) chloroplasts [Nicotiana tabacum cv. Xanthi and Lactuca sativa, romaine] by low temperature storage was investigated under a wide range of conditions to optimize long time activity retention. The more labile functions (photophosphorylation and electron transport) required very low temperatures (below -79.degree. C) and relatively high (above 20%, vol/vol) concentrations of cryoprotectives for satisfactory stabilization. Fluorescence induction and delayed light emission were less sensitive, especially during the 1st month of storage. Taking into account the effect of cryoprotectives on absolute activities prior to freezing, optimum activity retention was observed with a medium containing ethylene glycol (30%, vol/vol) and a storage temperature of -100.degree. C or below. In this case, given fast thawing and high chloroplast concentration, practially 100% preservation of all of the photosynthetic activities investigated was obtained for at least 10 months, even with very simple freezing and storage procedures. The same optimal medium at somewhat higher temperatures (-79.degree. C and to a lesser extent at -41.degree. C) caused a dramatic uncoupling effect: photophosphorylation was inhibited in a few hours, while electron transport increased 3- to 5-fold. The enhanced electron transport was stable for almost a month and then declined sharply. This uncoupling effect was specific only to ethylene glycol.