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 detached leaf or as an airdried plant. In detached leaves dehydration resulted in a lower relative water content in comparison with leaves dried on the plant. Water loss caused a reduction in chlorophyll, carotenoid and lipid contents and an increase in conjugated dienes. In detached leaves, ultrastructure was also affected by dehydration, showing damaged cells with altered chloroplasts which retained large quantities of starch and lipid-like inclusions in the stroma. Upon rehydration a continuous degradation of the chemical composition and cell organization was observed with a further increase in peroxidation. Leaves dehydrated on the plant showed degradation of chlorophyll and lipids, whereas carotenoids increased and conjugated dienes decreased. Desiccation caused a vacuolar fragmentation and a decline in starch, whereas chloroplasts underwent slight alterations. Following rewatering a full recovery of chlorophyll and lipids occurred, while carotenoids and dienes remained constant. Starch increased in the chloroplasts and there was complete recovery of the ordered cell arrangement and chloroplast organization. Of the chloroplast polar lipids, in both sets of leaves desiccation caused a reduction only in monogalactosyldiacylglycerol, while phospholipids 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, whereas detached leaves suffered a complete lipid degradation with the loss of polyunsaturated fatty acids.