Reorientation in Tilted Stems of Papaya by Differential Growth

Premise of research. Papaya (Carica papaya L.) is a fast-growing plant that is able to reorient quickly from a tilted position due to a local growth in the basal stem region. This seems to be a necessary adaptation in the struggle for light in the plant’s natural habitat, natural forest gaps. Interestingly, the stem anatomy of papaya consists exclusively of parenchymatous wood exhibiting substantial turgor pressure. The only reinforcing tissue is found in the bark, consisting of a lattice-like mesh of lignified fibers filled with parenchyma. This peculiar mechanism of reorientation raised questions concerning the role of turgor pressure during growth and the mechanical interactions between fiber mesh and parenchyma as a consequence of the unusual anatomy.Methodology. A set of mechanical measurements of sections of secondary phloem and xylem were conducted, comparing Young’s modulus and turgor pressure of the upper and lower sides of reerecting stems. Additionally, tissues from both sides were microscopica...