Underground system of the weed Stigmaphyllon blanchetii C. E. Anderson (Malpighiaceae) and its vegetative propagation role

Abstract Stigmaphyllon blanchetii is a perennial climbing species native to Brazil, mainly in the Northeast region, usually in sugarcane fields. Considered a weed, it presents aggressive reproduction and invasive behavior and can colonize sugarcane crops through stem and branch sprouts, resulting in several gaps at the beginning of planting and reducing the productivity of harvesting machines. However, the mechanism behind its invasive behavior, in which vegetative propagation through the underground organ plays an important role, is known. The objective of this work was to analyze whether the underground organ of S. blanchetii contributes to the rapid vegetative propagation of this species and define its structural origin and terminology through morpho-anatomical analyses. Morphological analyses were performed with the naked eye and under a stereomicroscope, and the structures were schematized and documented by means of images captured with a digital camera and illustrations. Anatomical analyses were performed using material fixed in FAA 70 and preserved in 70% alcohol. Histochemical tests were also performed. The results revealed that the underground structure is a complex and diffuse system composed of aerial stems, underground stems and three types of roots: primary, lateral, and adventitious. Due to the bipolar stem branching pattern, with aerial and underground branching, the underground structure of S. blanchetii was recognized here as a rhizophore and, through bud formation on hypocotyls and underground stems, it effectively participates in the vegetative propagation of the species.