Population dynamics ofHeloniopsis orientalis C. Tanaka (Liliaceae) in natural forests — Annual life cycle

Abstract

Annual changes in the leaves and reproductive organs ofHeloniopsis orientalis C. Tanaka (Liliaceae), a perennial evergreen herb, were studied from 1991 to 1997 in two areas of South Korea, Namhansanseong and Maranggol. The period for active growth in the leaves was from mid-March to early June. Average leaf angle was 70° in early June, decreasing to 50° in late October. From December until June of each following year, leaf angle was maintained a 0° to horizontal. The specific leaf area (SLA) value was 185 cm2.g-1 early in the growing season, increasing to 332 cm2g-1 in early June. By the end of October, SLA had decreased to 159 cm2g-1, after which it increased again from March to June. Because the SLA curve had two peaks, it was inferred thatH. orientalis possesses two means for survival: 1) an anti-freezing mechanism by which its leaves thicken during the winter, and 2) a reallocation of energy from old leaves to new leaves or to reproductive organs.H. orientalis flowered in a semi-enclosed state in late March. Blooming out of the bract, the front of the flower faced the ground. Growth of the peduncle ended in early June, at which point it was 60 cm long. At that time, the fruit was oriented so that the seeds were dispersed upward. Therefore one can see thatH. orientalis has two physiological features that enhance long-distance seed dispersal — a rather long peduncle relative to overall plant size and an upward seed-dispersal mechanism. In the Namhansanseong area, energy from the roots and old leaves was translocated to new leaves early in the growing season (from late March to early May). However, after mid-May, energy was re-translocated from new leaves to the roots. Moreover, the leaves on flowering plants grew more slowly than on non-flowering plants because energy was translocation to the reproductive organs. Therefore, new leaf growth depended on energy stores of the roots and the biomass of old leaves early in the growing season.