The ability of the root system of the poikilohydric plant Craterostigma plantagineum to survive
dehydration was investigated. The data presented here reveal that the root system is capable of surviving
dehydration, but shortly after
rehydration the root system senesces. Two weeks after
rehydration the growth of a complete new root system is initiated. During
dehydration sucrose accumulates from 36 to a maximum of 111 micromol g-1 DW in the roots. It is suggested that the accumulation of
sucrose protects the root system during
dehydration. There are major stores of
stachyose in the roots of Craterostigma (making up over 40% of the dry weight of the tissue) and during
dehydration these stores are metabolized. It is suggested that these
stachyose stores act as
carbohydrate reserves for the synthesis of
sucrose. However, over 350 micromol g-1 DW
stachyose is metabolized in the roots, which is well in excess of that required for the accumulation of
sucrose observed. It is likely that the
stachyose reserves in the root system are translocated to other regions of the plant to support carbohydrate metabolism during
dehydration of the tissue. During
rehydration, the
stachyose reserves return to their original level within 96 h. There is no change in the elevated
sucrose content of the roots over this period. Thus the roots maintain the protective properties of
sucrose much longer than they are needed. The maintenance of high
sucrose contents in rehydrating roots is discussed as a possible survival strategy against recurrent desiccation events.