Flowering phenology characteristics and floral longevity of Stellera chamaejasme in alpine grasslands

This study aimed to explore the evolutionary significance of flowering phenology and floral longevity of Stellera chamaejasme by measuring the flowering phenology and floral longevity at different biological levels (i.e., single flowers, inflorescences, and individual) in a natural population in the alpine grasslands on the eastern edge of the Qilian Mountains. The results showed that the studied population of S. chamaejasme flowered from mid-June to late July, and the flowering durations at the levels of population, individual, and inflorescence were 35 d, 18.97 d, and 9.80 d, respectively. The indexes of flowering synchrony at the individual and inflorescence levels were 0.86 and 0.78, respectively, with only one flowering peak at each level. The floral longevity at both the individual and inflorescence levels was significantly negatively correlated with the first flowering date. The floral longevity of single flowers significantly differed with position on an inflorescence; it was the longest for marginal flowers, shorter for flowers in the middle of the head, and the shortest for top flowers (i.e., flowers at the center of the inflorescence). In conclusion, S. chamaejasme was characterized by a “mass-flowering pattern,” and the floral longevity varied with flowering time and flower position on an inflorescence. This was likely an adaptive strategy of the species to maximize reproductive fitness in harsh alpine environments.