Comparisons of growth schedule, reproductive property and allocation pattern among three rhizomatous Polygonatum species with reference to their habitat types

Phenology, reproductive traits and dry matter allocation were compared among three rhizomatous Polygonatum species (Liliaceae) growing in different habitats. Polygonatum odoratum var. maximowiczii grows mainly on the floor of deciduous forests; Polygonatum involucratum at forest edges with patchy light spots; and Polygonatum humile in moist grasslands with sparse vegetation cover. The purpose of this study was to describe the growth patterns and reproductive traits of related species for the consideration of habitat-specific responses of life-history traits. The leaf emergence and reproductive phenology of P. odoratum progressed more rapidly and the growth season was shorter in comparison with other species, reflecting seasonal changes in light conditions in the understory. Every species showed very low selfing ability but the evidence of pollen limitation was negligible under natural pollination. Dry matter allocations to above- and below-ground parts were similar among species but the patterns of annual resource allocation varied greatly: P. odoratum showed large annual shoot production but annual rhizome growth was small (3-4 cm/year). The lifespan of rhizomes was >8 years in this species, whereas it was 34 years in other species. The annual growth of rhizomes in P. humile was large (15.5 cm/year) and branching was frequent, indicating rapid vegetative expansion under unstable conditions. The leaf/stem ratio was large in P. humile and small in P. odoratum. The allocation and growth pattern of P. involucratum were intermediate. Such differences in growth and allocation patterns among the three Polygonatum species could reflect the possible directions of life-history strategy against specific light conditions and habitat stability, although phylogenetic constraints should be taken into account for the interspecific comparison.