Growth responses and adaptations of the emergent macrophyte Acorus calamus Linn. to different water-level fluctuations

Abstract

Acorus calamus Linn. was grown under four water-level fluctuation (WLF) treatments to study the influence of WLF on the growth of the species. The four WLF treatments (designated as 0 cm, 60 cm, 60 ± 30 cm, and 60 ± 60 cm) were initiated with the minimum water levels (0, 60, 30, and 0 cm, respectively) for a week and then switched to the maximal water levels (0, 60, 90, and 120 cm, respectively) one week later. This cycle was repeated six times during 12 weeks. Relative growth rate (RGR), biomass allocation, shoot and below-ground morphology, chlorophyll content, and concentrations of proline, malondialdehyde (MDA), and soluble sugar (SS) of A. calamus were measured. After the 12 weeks' WLF treatment, growth rate differed among the treatments. RGR was negative in the 60 cm treatment. A. calamus showed significant morphological adaptations to WLFs, including different patterns in length, blade length, width and numbers of shoots. The root:shoot ratio was significantly greater in the 0 cm treatment with no significant differences among the other three WLF treatments. SS concentrations in the rhizome and root were higher in the 60 ± 60 cm treatment than in either the 60 cm treatment or 60 ± 30 cm treatment. No clear relationship was found among the treatments for chlorophyll concentrations, proline, or MDA concentrations in the shoots but fluctuating water levels significantly stimulated proline and MDA accumulation. The differences in biomass and morphological variables among treatments suggested that WLF is an important regulator of the growth of A. calamus and that the species is better adapted to cyclic WLFs than to constant deep water.

Keywords:

• water-level fluctuations
• biomass production
• biomass allocation
• shoot morphology
• root morphology
• Acorus calamus

Acknowledgements

The authors would like to sincerely thank professor Zhang Yongyuan and Mohammad Russel for their comments and suggestions. The assistance of Wu juan, Ge Fangjie, Wei Hehong, Tang Haibin, and Zhu Guorong are also acknowledged.

Funding

This work was supported by Major Science and Technology Program for Water Pollution Control and Treatment [grant number 2009ZX07106-003], [grant number 2011ZX07303-001].