TITLE:
Effects of Salinity on Germination, Seedling Growth and Ecological Properties of Phragmites australis Communities in the Estuary of the Chikugogawa River, Southwestern Japan
AUTHORS:
Akira Haraguchi
KEYWORDS:
Common Reed; Germination; Salt Marsh; Salt Tolerance
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.5 No.5,
March
11,
2014
ABSTRACT: Salt tolerance of Phragmites australis populations was investigated in natural reed
habitats in the estuary of the Chikugogawa River, southwestern Japan. P. australis populations were selected
along the salinity gradient in the estuary, including limnetic (salinity
0.05%), oligohaline (0.4%) and polyhaline sections (2.5%). The ratio of
Total-P/Total-N of river water showed high values in the oligohaline section
and the above ground biomass, population height and culm diameter of P. australis showed maximum values in
this section. Sufficient phosphorus supply could sustain the high productivity
of the community in the oligohaline section, irrespective of the salinity of inundated
water. The seed production of P.
australis was lowest in the polyhaline section. Thus, the ecological
performance of P. australis was
highest in the oligohaline section and the performance declined with the
increasing salinity of the habitat. The effects of salinity on germination and
seedling growth were evaluated by means of cultivation in 0.0% -5.0% (NaCl w/w%) salinity medium. Seeds of P. australis collected from every
natural population in the estuary failed to germinate at salinity levels above
2.3%. Growth of shoot length and above-ground biomass of seedlings germinated
in the fresh water medium were measured for 21 days’ exposure to constant
salinity solutions ranging from 0.0% -5.0%. Although mortality was high at salinity
levels 3.5% and 5.0%, elongation of shoots of some plants was evident at a
salinity level of 5.0%. Seeds from the population in the limnetic section never
germinated at a salinity of 3.5%, whereas seedlings obtained from the seeds of
the same population germinated in freshwater conditions grew under a salinity
of 3.5%. Thus, P. australis seedlings
have higher salt tolerance compared to that during the germination stage of the
seeds. In this study, it is clarified that P.
australis has low salt tolerance during the germination stage and then it
acquires salt tolerance during the stage of seedling growth.