|Publication Type:||Journal Article|
|Year of Publication:||2008|
|Authors:||Araki, S., Kunii H.|
|Journal:||Plant Species Biology|
Carex rugulosa Kuk. develops riverside vegetation in brackish marshes along the lower parts of rivers. Because the rhizomatous ramets grow densely (590-950/m(2)) in its developed population, it is expected that seedlings cannot get enough light to grow if seeds germinate in crowded ramets. We studied the reproductive contribution of seed in a marshy meadow of the Ohashi River, Japan. The number of seeds produced was 6900-14 200/m(2) in 2002. The number of buried seeds in the following germination season differed among sites from 1190 to 2690/m(2). No seedlings were observed at plots where the ramets from rhizomes grew densely. In contrast, seedlings appeared in plots where all rhizomatous ramets were artificially cut. The number of seedlings corresponded to 17.5-39.5% of that of buried seeds. All these seedlings were submerged and died when it rained heavily. In the genotype analysis using allozyme detection, one of the phosphoglucoisomerase loci (Pgi-2) indicated a pair of alleles. Among eight plots (each plot was 50 or 60-cm square), four showed an excess of heterozygotes and two showed homozygote domination in the Pgi-2 genotype. These results suggest that: (i) seed germination is suppressed in crowded ramets; (ii) seedling survival is severely reduced by inundation; and (iii) the population is usually maintained by clonal growth. As germination is induced in open areas, it is hypothesized that the main role of seed is recovery after vegetation decline caused by environmental stresses or colonization to other areas without dense vegetation.