Submerged plant growth is limited by the reduction of underwater photosynthesis attributed to low CO2 availability, as well as light limitation associated with underwater conditions. Heterotrophic bacteria and fungi play an important role in local aqueous dissolved inorganic carbon (DIC) content surrounding submerged plants. In order to investigate the effects of carbon conversion in plant–microbe interactions on plant growth, in the present study we inoculated the plant medium of Vallisneria natans with Pseudomonas putida KT2440 and measured carbon conversion in the system, as well as several indices of plant growth. The quantity of P. putida KT2440 increased twofold because of the availability of organic matter produced by V. natans. Similarly, P. putida KT2440 supplied DIC for V. natans, improving its photosynthetic rate. Moreover, the significantly higher leaf area, specific leaf area and fresh biomass of V. natans attributed to the presence of P. putida KT2440 demonstrated that the interaction between V. natans and P. putida enhanced the efficiency of nutrient and CO2 uptake by V. natans, promoting V. natans growth. Therefore, we suggest that the carbon and oxygen microcycle based on the protocooperation of V. natans and P. putida KT2440 may accelerate the transformation of carbon to increase carbon availability to promote the growth of both plant and microbe.
Peer Review #2 of "Effects of substrate and water depth of a eutrophic pond on the physiological status of a submerged plant, Vallisneria natans (v0.2)"