Background and objectives
Balanophoraceae is one of the most bizarre and biologically interesting plant clades. It groups species with peculiar features that offers an opportunity for investigating several aspects of parasite plant development and morphogenesis. We analyzed the development and the mature vegetative body of Lathrophytum. peckoltii Eichler, focusing on the formation of the host-parasite interface. Additionally, we analyzed how this parasitic interaction causes modifications to the anatomy of Paullinia uloptera Radlk and Serjania clematidifolia Cambess host roots.
Methods
Vegetative bodies of parasite at different developmental stages were collected while infesting the roots of Sapindaceae vines. Non-parasitized host roots were also collected for comparison. Light, epifluorescence, confocal, and scanning electron microscopy were used to analyze.
Key results
The vegetative axis’ initial cells divide repeatedly, originating a parenchymatous matrix, which occupies the space from the cortex to the vascular cylinder of the host’s root. In the matrix’s peripheral layers, located near the xylem of the host’s roots, a few cells initiate the process of wall lignification, originating parasitic bundle. The vascular cambium of the host’s root changes the division plane and becomes composed by fusiform initials, forming the vascular bundle. The vegetative axis presents a dermal tissue similar to a phellem, parenchymatous matrix and a vascular system with different origins.
Conclusion
The parasite reproduces by endophytic development, in a manner similar to that observed for endoparasites. The strategy of late cell differentiation could aid the parasite in avoiding early detection and triggering of defense responses by the host. This development causes changes to the host root cambial activity, leading to the establishment of direct, vessel-to-vessel connection between host and parasite. We associate these changes to the cambium modularity and an influx of parasite-derived hormones into the host cambium.