## 4 Discussion  
### Varying Flooding Durations Affect Root Morphology  
Under flooded conditions, plants make necessary adjustments to their growth characteristics and root morphology to mitigate the stress caused by flooding [24]. Different plant  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Species** & **Parameters** & **Equation** & **R2** & **Significance** \\ \hline \multirow{2}{*}{_Carex_} & Friction angle & \(y=27.84+2.86\times 10^{-3}x-2.09\times 10^{-5}x^{2}\) & 0.74 & \textless{}0.05 \\  & Cohesion & \(y=23.08+6.92\times 10^{-2}x-42\times 10^{-4}x^{2}\) & 0.83 & \textless{}0.01 \\  & Friction angle & \(y=23.54-7.77\times 10^{-3}x+1.28\times 10^{-5}x^{2}\) & 0.92 & \textless{}0.01 \\  & Cohesion & \(y=31.02-1.73\times 10^{-3}x-2\times 10^{-4}x^{2}\) & 0.97 & \textless{}0.01 \\  & Friction angle & \(y=22.39-2.22\times 10^{-2}x+7.87\times 10^{-5}x^{2}\) & 0.96 & \textless{}0.01 \\  & Cohesion & \(y=32.04+0.25x+5.99\times 10^{-4}x^{2}\) & 0.94 & \textless{}0.01 \\  & Friction angle & \(y=20.36-1.22\times 10^{-2}x+1.92\times 10^{-5}x^{2}\) & 0.97 & \textless{}0.01 \\  & Cohesion & \(y=18.76-0.18x+6.57\times 10^{-4}x^{2}\) & 0.95 & \textless{}0.01 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Fitting equation for soil strength indicators and flooding duration.  
Figure 8: Effect of varying flooding durations on soil strength indicators in plants: (**A**) represents friction angle; (**B**) represents cohesion; CK is the no-plant flooding control.  
species exhibit varying response strategies to flooding stress. Although all three plants belong to the'static type', which is better adapted to flooded environments--reducing their energy consumption while enhancing their adaptability to flooding stress without significant morphological changes [25; 26], their root systems do not respond uniformly to flooding stress. Specifically, _Carex_ and _Cynodon_ reached their growth inflection points after 120 days of exposure, while _Eleusine_ reached its inflection point after 60 days. There was a further increase in the proportion of smaller-diameter-class roots for _Carex_, along with an increase in the proportion of _Cynodon_ roots greater than 0.5 cm in diameter. This suggests that both species experienced accelerated root growth and increased belowground biomass allocation under flooded conditions [27; 28]. The two species differed in their growth patterns and root system distribution, with _Carex_ producing more adventitious roots by promoting the growth of small-diameter-class root systems. With the exception of _Carex_, the small-diameter-class root system gradually dominated as a percentage of the total root system as the duration of flooding increased, while the opposite trend was observed for _Carex_. The total tensile strength and elastic modulus of the individual roots of the same plants increased with prolonged flooding duration; however, those of _Eleusine_ gradually decreased, reaching a maximum value at 60 days. This trend in root system growth was also observed in _Carex_. The observed growth trend is responsible for the increase in the mechanical properties of individual roots within large-diameter root systems at the onset of flooding [29]. We speculate that the root systems of _Carex_ and _Cynodon_ were able to maintain some structural integrity and functionality to support plant growth and nutrient uptake in a flooded environment. In contrast, _Eleusine_ exhibited a markedly different response strategy, showing an adaptive response within the first 30 days of flooding by eliminating small-diameter-class roots and further consolidating large-diameter-class roots. However, this adaptation was short-lived, and after 90 days of flooding, there was a significant decrease in activity and a substantial shedding of small-diameter roots.