Vegetative fragments represent one of the most important mechanisms for the reproduction and spread of aquatic plants. But the success of fragment colonization strongly depends on the characteristics of a given species and several environment factors. Fragment size, nutrient and density are all important factors influencing the colonization of aquatic plants, while, their interactive influence on plant colonization is far from clear.

A research team led by Prof. XIE Yonghong from Institute of Subtropical Agriculture, the Chinese Academy of Sciences (ISA) recently focused their investigation on this aspect. Under two different sediment types, they grew a typical submerged macrophyte Myriophyllum spicatum with two fragment sizes and two densities to test the interactive effect. The morphological (relative growth rate [RGR], relative elongation rate [RER], branching number, shoot diameter and biomass allocation) and physiological characteristics (total N content and total P content in the shoot and root) were also investigated.

Their result showed that, rather than fragment size, the RGR of M. spicatum was significantly influenced by plant density and sediment type, and decreased with increasing plant density in the mud treatment. In contrast, plant density had an insignificant effect on RGR in the sand treatment. The RER of M. spicatum decreased significantly with increasing plant density and fragment size, and which was much higher in the mud treatments compared to the sand treatments.

Branching number was greater in the mud treatments compared to the sand treatments. Shoot diameter increased with decreasing plant density and increasing fragment size, especially in the mud treatments. Total N content in the shoot and root was much higher in the mud and low-density treatments than in the sand and high-density treatments. While, shoot P content only decreased with increasing plant density. In comparison, root P content was much higher in the mud and low-density treatments than in the sand and high-density treatments.

"These data indicate that fragment colonization by M. spicatum is improved by large fragments, low density, and nutrient-rich sediments", said LI Feng, a researcher in XIE’s team, “and that these conditions contribute to the rapid population expansion of this species.”

This study was supported by the National Key Technology Research and Development Program of China (2014BAC09B03), the Major Special Project of Water Pollution Control and Water Environmental Management (2012ZX07204004-002), the Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection (ERESEP2015K20), the National Natural Science Foundation of China (31200271), the Knowledge Innovation Program of the Chinese Academy of Sciences (ISACX-LYQY-QN-1208).

The study entitled "Colonization by fragments of the submerged macrophyte Myriophyllum spicatum under different sediment type and density conditions" has been published in Volume 5, June 2015 of Scientific Reports, details could be found at http://www.nature.com/srep/2015/150702/srep11821/full/srep11821.html.