Abstract: Aims Fritillaria unibracteata is a precious and endangered medicinal plant. Due to long-term excessive bulbs exploitation, its wild plant resources have been gradually decreasing. This study was aim to explore the growth status of F. unibracteata and the content characteristics of medicinal components in bulbs at different altitudes, especially at low altitudes. it was contribute to expand artificial planting areas of F. unibracteata, and alleviate the severe contradiction between supply and demand in the market. Methods This study carried out a two-year field pot experiment of F. unibracteata at five altitudes from low altitude (1170 m) to high altitude (3410 m). We measured phenological index and morphological characteristics of F. unibracteata, and the contents of total alkaloids and total saponins in burbs. Important findings The results indicated that the germination stage, leaf spreading stage and flowering stage of F. unibracteata were highly significantly advanced with the decreased altitude (P<0.01), while the wilting period was delayed first and then advanced with the decreased altitude. The length of growing season increased first and then decreased with the decreased altitude, and the longest value was (105.80 ± 4.87) days at 3080 m above sea level (asl). The plant height and single leaf area increased first and then decreased with the decreased altitude, while the specific leaf area decreased first and then increased. The individual bulb biomass increased first and then decreased with the decreased altitude, and the maximum value was (1.40 ± 0.29) g at 3080 m asl. The contents of total alkaloids and total saponins in bulbs decreased first and then increased with the decreased altitude. There was no significant difference in the content of total alkaloids in bulbs above 2370 m asl (P>0.05), and the contents were all higher than 0.70 mg/g. This study found that appropriately reducing the planting altitude of F. unibracteata was helpful to prolong the growth season, increase plant height and leaf area, and promote the accumulation of bulb biomass. The results suggested that considering the differences of bulb biomass and medicinal component content of F. unibracteata at different altitudes, its suitable planting range at low altitude could be selected from 2370 m to 3080 m asl.

Key words: medicinal plant, phenology, morphological characteristics, altitude gradient, artificial planting