Characteristics of the flowering parts and breeding characteristics of <italic>Houttuynia cordata</italic>

Houttuynia cordata is a significant medicinal and edible plant in China. Its long-term reliance on vegetative propagation has led to harmful mutation accumulation and germplasm degradation. To elucidate the mechanisms underlying the barriers to sexual reproduction in H. cordata, this study systematically observed floral characteristics and phenology of flowering. It combined I2-KI staining, in vitro culture medium, and benzidine-hydrogen peroxide methods to detect pollen viability and stigmatic receptivity, and analyzed the process of microsporogenesis through paraffin sectioning. The results indicated that the flowering period of individual H. cordata plants lasted 35 days, the inflorescence flowering period was 12 days, and the duration of a single flower was 6–7 days. The flowering order of the spike inflorescence on the reproductive branch was from bottom to top, and the individual flower was bisexual without perianth. The detection results of pollen activity and stigmatic receptivity showed that the extremely low pollen activity hindered the smooth progress of sexual reproduction in H. cordata. Paraffin sectioning results revealed that abnormal tapetal degradation blocked the development of microspores, eventually causing pollen abortion. It can be seen that male sterility is the internal cause of seed abortion in H. cordata. This study provides a theoretical basis for the artificial propagation and resource protection of H. cordata.