The effect of floral morphology on seed set in Carthamus tinctorius Linnaeus (Asteraceae) clones of Sichuan province in China

Abstract

The relationships among the floral morphologies, breeding system and pollination insects in nine Carthamus tinctorius L. clones were investigated in Ya’an, Sichuan province, China. No significant differences in seed setting rate were observed among the clones following unbagged treatment, but significant differences in seed setting rate were observed among the clones following bagged treatment. Breeding experiments indicated that both reproductive systems (selfing and outcrossing) coexisted in each tested C. tinctorius clone. It exhibited reproductive assurance through automatic self-pollination, which might be an important factor in enhancing the amount of seeds. Among 17 species of visitors, the main effective pollinators were Apis cerana Fabricius, Apis mellifera Linnaeus and Eristalis tenax Linnaeus. All floral morphology traits (corolla length, corolla diameter, pistil length, anther length, stigma length, and stigma–anther separation) showed significant variations among the clones. However, only corolla diameter showed a significant negative correlation with the frequency of pollinator visits and a positive correlation with seed set following unbagged treatment. There was a negative correlation between stigma–anther separation and seed set, and although this was not significant, it could be argued that if a pistil developed that was too long, seed set would decline under natural conditions. Corolla length was significantly positively correlated with stamen and anther length, and corolla diameter was significantly negatively correlated with pistil length. Stigma length was also significantly positively correlated with stamen length. These findings indicate that corolla diameter could significantly affect seed set in C. tinctorius under the conditions in Ya’an, China, and corolla diameter affects seed set by the combined effect of multiple traits.