Substrate screening for cutting propagation of emergent Rotala rotundifolia

Rotala rotundifolia is an aquatic plant as an emergent and submerged species. By leveraging its unique ability to transition from emergent to submerged growth, it can rapidly establish submerged plant communities and thus holds strong potential for water ecological restoration. We used five different substrates for cutting propagation, namely yellow soil (T₁), paddy soil (T₂), river sand (T₃), river sediment (T₄), and a mixture of nutrient soil and river sand (T₅, in a volume ratio of 1:1), to investigate the growth responses of R. rotundifolia, focusing on variables including plant height, number of branches, biomass, root morphology, and chlorophyll fluorescence characteristics. Then, we identified the most suitable substrate for cultivating emergent R. rotundifolia. The results showed that all cuttings in the T₅ group died within 15 days, which was not suitable for cultivation. Plant height (27.06±3.08 cm) and fresh weight (1870±304 mg) of the T₂ group were increased by 25.5%, 47.1%, 100.9% and 111.3%, 124.8%, 251.3% compared with the T₁, T₃, and T₄ groups, respectively. Total root length, root surface area, root volume, and root activity of the T₂ group were increased by 41.7%-164.7%, 38.8%-164.7%, 31.6%-177.8%, and 16.2%-113.3%, respectively. The number of branches, chlorophyll content, actual photochemical efficiency, and maximum photochemical efficiency of the T₂ group were significantly higher than those of the other groups. Plants in groups T₃ and T₄ exhibited dwarf phenotypes with varying degrees of chlorosis and wilting. Root growth and development of R. rotundifolia were significantly positively correlated with the available phosphorus and available potassium in the substrate. The comprehensive evaluation of the substrates by principal component analysis was ranked as T₂>T₁>T₃>T₄, indicating that paddy soil is more suitable as a substrate for the cutting propagation of R. rotundifolia.