DESICCATION-TOLERANT SPOROBOLUS-STAPFIANUS - LIPID-COMPOSITION AND CELLULAR ULTRASTRUCTURE DURING DEHYDRATION AND REHYDRATION

The desiccation-tolerant plant Sporobolus stapfianus was subjected to slow dehydration and to rehydration either as a silica gel-dried detac hed leaf or as an air-dried plant. In detached leaves dehydration resu lted in a lower relative water content in comparison with leaves dried on the plant, Water loss caused a reduction in chlorophyll, carotenoi d and lipid contents and an increase in conjugated dienes. In detached leaves, ultrastructure was also affected by dehydration, showing dama ged cells with altered chloroplasts which retained large quantities of starch and lipid-like inclusions in the stroma, Upon rehydration a co ntinuous degradation of the chemical composition and cell organization was observed with a further increase in peroxidation, Leaves dehydrat ed on the plant showed degradation of chlorophyll and lipids, whereas carotenoids increased and conjugated dienes decreased. Desiccation cau sed a vacuolar fragmentation and a decline in starch, whereas chloropl asts underwent slight alterations. Following rewatering a full recover y of chlorophyll and lipids occurred, while carotenoids and dienes rem ained constant, Starch increased in the chloroplasts and there was com plete recovery of the ordered cell arrangement and chloroplast organiz ation. Of the chloroplast polar lipids, in both sets of leaves desicca tion caused a reduction only in monogalactosyldiacylglycerol, while ph ospholipids showed an opposite pattern, increasing in air-dried leaves and decreasing in detached leaves. Rewatering of leaves desiccated on the plant led to a complete recovery of the lipid composition, wherea s detached leaves suffered a complete lipid degradation with the loss of polyunsaturated fatty acids.