Effects of pappus removal and low-temperature short-term storage on interspecific and intraspecific variation in seed germination of Luobuma

Seed germination rarely occurs in Luobuma (Apocynum venetum, Poacynum pictum and P. hendersonii) under natural conditions. The present study was conducted to assess interspecific and intraspecific variation in seed germination and the effect of pappus removal and low-temperature short-term storage on seed germination of Luobuma. The study identified significant differences in germination percentage, germination index, time to 50% germination, bud length and root length between three Luobuma species Apocynum venetum, Poacynum pictum and P. hendersonii, and between six ecotypes of P. pictum. The highest seed germination percentage was recorded in A. venetum (> 90%) followed by P. pictum (53-66%), while the lowest was recorded in P. hendersonii (26-34%). Among the different ecotypes of P. pictum, Pp-BMX recorded the highest seed germination percentage, while Pp-BMQ recorded the lowest. In addition, the intraspecific variation in germination was considerably more than the interspecific variation under different treatments. Pappus removal increased the germination percentage of Luobuma seeds, which indicates that pappus acts as a mechanical barrier to germination. Low temperature significantly reduced (P < 0.05) the time to 50% germination of A. venetum and P. hendersonii seeds compared with seeds with and without pappus.