Abstract:

In order to understand the relationship between biomass and nutrient allocation of Lilium pumilum, a wildly spread perennial herb in China mainly used for medicinal purposes (bulbs are harvested) and as an ornamental, a study on the biomass of vegetative organs, reproductive organs and allocation of N and P in different developmental stages was carried out . The experimental material was obtained from the garden of Northeast Forestry University where L. pumilum had been seeded in a high bed of black soil in spring 1998 under conditions of full sunlight and received treatment of manual weeding, watering and no fertilization.In 2000, samples were taken from May to November from blooming plants of L. pumilum at 6 different stages: bud stage (May 24th); middle period of bud spreading (June 11th); floral phase (June 26th); early fruit-set phase (July 26th); fructescence (August 29th); and seed maturation phase (October 3rd). Thirty individual plants together with their intact underground organs were carefully washed. Every plant was divided into bulb, stem, leaf, bud, flower and fruit (shell and seed), placed into envelopes, dried at 80 ℃, and weighed. We determined the mean biomass of each organ at each growth period and then calculated the ratio of the mean biomass to total biomass. Also, two replicate samples of each tissue were analyzed for N and P content and the average percentweight of total-N and total-P was recorded.The results showed that the percent mean biomass averaged across all developmental stages decreased in the following order: bulbs (60.17%): leaves (13.28%): stems (12.84%): reproductive organs (9.18%); and roots (5.78%). The large investment in the bulb might be a self-protective mechanism for a population of perennial bulbaceous plants as a means for maintaining their long term development. The bulb reached maximum biomass at the early bud stage, and seed maturation phase and the minimum at floral stage. If we want these results indicate that to harvest edible bulbs, the fruitlet should be removed at the post floral stage to increase bulb biomass at the post floral stage and thus improve the bulb harvest. Bulbs should be harvested at the period of maximum biomass, that is, at the bulb stage and seed maturation phase. Seasonal biomass dynamics of reproductive organs were negatively correlated with non-reproductive organs.The results revealed that the mean percent total-N in tissues averaged across all development stages decreased in the following order: leaves (2.19%); reproductive organs (1.50%); bulbs (1.16%); roots (1.03%); and stems (0.99%). Total-N tissue concentrations reached their peak during leaf sprouting and early leaf spreading phase; this occurred when the N content of the reproductive organs were positively correlated with leaf N content and negatively correlated with that in the bulb. The mean total-P content decreased in the following order: reproductive organs (0.035 6%); bulbs (0.031 6%); stems (0.027 8%); roots (0.026 6%); and leaves (0.026 4%). The total-N content of the reproductive organs was positively correlated with that in the stem. This research also revealed that the content of total-N and total-P in aboveground organs tended to increase while organs underground tended to decrease with changing seasons.

Key words: Lilium pumilum, Reproductive allocation, Biomass, Nutrient element