The effect of submergence on ontogeny of cambium and secondary xylem and on fiber lignification in inflorescence stems of Arabidopsis

The inflorescence stem of Arabidopsis thaliana is characterized by a wavy r ing of lignified fibers inward to the cortex. In young stems, primary fiber s develop from the ground meristem, forming the outer part of the pith, whi le in mature stems the fiber system is comprised both of these primary fibe rs as well as secondary ones that differentiate from the cambium. Typically , the cambium formed in the inflorescence stem is not always continuous. Th erefore, the secondary xylem and the secondary parts of the wavy band of fi bers are usually formed only in sectors at the circumference. Submergence o f the developing inflorescence stem arrests both the lignification of the w avy band of primary fibers and the development of the cambium. The arrest o f cambial ontogeny and fiber lignification by environmental conditions offe rs new avenues to study the cascade of genes involved in cambial initiation and fiber lignification.