UNUSUAL COMPOSITION OF THYLAKOID MEMBRANES OF THE RESURRECTION PLANT BOEA-HYGROSCOPICA - CHANGES IN LIPIDS UPON DEHYDRATION AND REHYDRATION

Boea hygroscopica is a resurrection plant that is able to pass from bi osis to anabiosis and vice versa following slow dehydration, but loses this ability following a rapid water loss. Fresh leaves were detached from plants grown in well-watered conditions and subjected to either rapid or slow dehydration and rehydration. Upon rehydration only slowl y dried leaves revived. Analysis of thylakoid membranes revealed a rat her small amount of total lipids (1.4-2 mu mol g(-1) dry weight) in co mparison with other flowering plants. The main glycolipid was digalact osyldiacylglycerol (DGDG) rather than monogalactosyldiacylglycerol (MG DG) as is common in higher plants. Linoleic acid was the main fatty ac id (30-40 mol% of total fatty acids), while linolenic acid was present from 14 to 26 mol%. In both the fresh and rehydrated leaves nearly al l lipid components were present in similar amounts. Following dehydrat ion the DGDG/MGDG molar ratio, which was 1.1 in control and rehydrated leaves, doubled by the end of the rapid drying period and was three t imes as high in slowly dried leaves. The total polar lipid/free sterol molar ratio as well as the free fatty acid level assumed the highest values in the rapidly dehydrated leaves. A shift towards the more unsa turated fatty acids was observed in all lipid classes upon dehydration irrespective of whether it was slow or rapid. Our data show only smal l differences between rapidly and slowly dehydrated leaves which can b e correlated to the capacity of slowly dehydrated leaves to revive.