Low-molecular weight substances in the poikilohydric plant Ramonda serbica during dehydration and rehydration

Abstract

The desiccation-tolerant plant Ramonda serbica Panc. was subjected to dehydration by withholding water for 13 days and then rehydrated by rewatering for 72 h. Dehydration reduced the relative water content (RWC) from 97% in the fully hydrated plants to 4% in the desiccated ones, plants regaining the initial RWC upon complete rehydration. The decrease in the osmotic potential at full turgor from −0.7 MPa in the control plants to −2.2 MPa in the desiccated leaves indicates that an osmotic adjustment came into play. The osmotic adjustment in the dried leaves was due primarily to the high concentration of inorganic ions (71% of total solutes), especially K+ and Cl−. Other detected compounds such as soluble sugars and free amino acids gave a rather low contribution to the osmotic potential at full turgor of the desiccated leaves. Generally, upon rehydration all the osmotically active substances almost returned to their initial concentrations. The presence of increased amounts of sucrose detected during desiccation is discussed in relation to its role in membrane stabilisation.