Explaining species distribution pattern along environmental gradients has been a dominant subject in ecological research for decades. Many abiotic habitat conditions (e.g., salinity, water level, soil nutrients) and biotic factors (e.g., competition, facilitation and grazing) have been discussed as important drivers of the spatial variation in wetland plant distribution. Among them, flooding is considered the most important factor in determining plant distribution, mainly due to the reduced oxygen availability in the soil. However, wetland plants, especially in floodplains and river-connected lakes, also experience periodic drought stress because of large water level fluctuation. To date, the role of drought events in determining plant distribution has been paid more and more attention.
Here, a greenhouse experiment was conducted in the Institute of Subtropical Agriculture, Chinese Academy of Sciences (ISA), by Doctor LI Feng. The aim of this experiment was to elucidate the physiological mechanisms of plant distribution patterns by investigating the physiological responses of three typical wetland plants to flooding and drought in Dongting Lake. To this end, the three typical wetland plants were treated with three water levels (flooding, 25 cm; control, 0 cm; drought, -25 cm), and relative growth rate (RGR), malondialdehyde (MDA) content, electrolyte leakage and proline content were investigated.
After treated 70 days, researchers found that RGR of the three species decreased significantly in both flooding and drought treatments. Compared to the control, RGR of M. sacchariflorus decreased more in the flooding treatment but less in the drought treatment compared to the other two species. The contents of MDA in the three species increased in both flooding and drought treatments, except for P. hydropiper in the flooding treatment. MDA contents increased more in M. sacchariflorus in the flooding treatment but less in the drought treatment compared to the other two species. Only M. sacchariflorus had a higher electrolyte leakage in the flooding treatment, and drought led to a higher electrolyte leakage in P. hydropiper and C. brevicuspis. Proline content increased 69.2%, 66.7% and 39.6% in P. hydropiper, C. brevicuspis and M.sacchariflorus in the flooding treatment, and increased 44.2%, 13.0% and 45.3% in the drought treatment, respectively. These results suggest that M. sacchariflorus has a higher tolerance to drought but a lower tolerance to flooding than do the other two species.
This study was supported by the Knowledge Innovation Program of the Chinese Academy of Science (KZCX2-YW-435), the National Basic Research Program of China (2012CB417005) and the National Natural Science Foundation of China (31200271; 31070325).
The study entitled “Physiological mechanisms for plant distribution pattern: responses to flooding and drought in three wetland plants from Dongting Lake, China” has been published in January 2013 in Liminology, details could be found at http://link.springer.com/article/10.1007/s10201-012-0386-4