Abstract:

simulating soil submergence in the hydro fluctuation belt of the Three Gorges Reservoir Region, four different kinds of water treatment were applied to investigate the change in malic acid, shikimic acid, and biomass in the roots of Taxodium ascendens seedlings (all data being calculated in dry mass). The main purpose respectively of this study was to explore the mechanism of the plants metabolic adaptation to water level changes. The four water treatments respectively were: normal growth water treatment (CK), light drought water stress (T1), soil water saturation (T2) and soil submersion (T3).
The results showed that there was no significant difference in content of malic acid and shikimic acid, and in biomass in the taproot between CK and T1,T2 or T3. The content of malic acid in the lateral root in both T2 and T3 was 1.7 and 2.2 times higher than that in CK. Furthermore, the average content of malic acid in the whole root system in both T2 and T3 was also 0.8 and 1.5 times higher than in that of CK. However, the mean content of malic acid in the lateral root or whole root in T1 was not significantly different from that in CK. Compared to CK, the mean content of shikimic acid in the lateral root in T2 and T3 increased by 0.4 and 1.1 times respectively, whereas that in T1 was 0.5 times less than that in CK. Although the mean content of shikimic acid in the whole root system in T2 and T3 respectively appeared higher than that in CK, no significant difference with CK was found. On the contrary, T1 significantly exhibited a 0.3 times lower in mean content of shikimic acid in the root system than CK. In comparison with CK, both T2 and T3 demonstrated no significant differences in biomass of the taproot, lateral root and the whole root system, respectively, but T1 showed a significant increase in biomass of the lateral root and the whole root systemA highly positive relationship was displayed between mean content of malic acid and mean content of shikimic acid in the whole root system (P<0.01). The mean content of shikimic acid in the whole root system was negatively correlated with the biomass of the whole roots (P<0.05).

Key words: soil dynamic submergence, Taxodium ascendens seedlings, malic acid, shikimic acid, biomass, Three Gorges Reservoir Region, hydrofluctuation belt