Lev-Yadun, S., Department of Biology, Fac. of Sci. and Science Education, University of Haifa - Oranim, Tivon 36006, Israel
Flaishman, M.A., Department of Biology, Fac. of Sci. and Science Education, University of Haifa - Oranim, Tivon 36006, Israel

The inflorescence stem of Arabidopsis thaliana is characterized by a wavy ring of lignified fibers inward to the cortex. In young stems, primary fibers develop from the ground meristem, forming the outer part of the pith, while in mature stems the fiber system is comprised both of these primary fibers as well as secondary ones that differentiate from the cambium. Typically, the cambium formed in the inflorescence stem is not always continuous. Therefore, the secondary xylem and the secondary parts of the wavy band of fibers are usually formed only in sectors at the circumference. Submergence of the developing inflorescence stem arrests both the lignification of the wavy band of primary fibers and the development of the cambium. The arrest of cambial ontogeny and fiber lignification by environmental conditions offers new avenues to study the cascade of genes involved in cambial initiation and fiber lignification.