title: The ontogenetic trends of microtuber formation in potato (Solanum tuberosum L.).
abstract: The main aim of this investigation is the understanding of how microtubers are formed out of auxiliary buds in induced conditions. In the induced buds, meristematical cells with high cytoplasmic and nuclear stain ability expand deeper into the inner sections of the buds, comparing with non-induced buds, which the area is restricted to the apical regions. The first sign of microtuberization is the increase in size of cortical parenchyma cells in lower section and also increase in mitosis divisions in inner sections of the meristems. Most of the growth rates occur in the induced medium along the length and the width of the cells. It is also considered that the diametric growth of the tubers and the base of the leaves on the tubers begin their radial growth. The cortical parenchyma cells begin forming amidon grains during their vacuolar extension at extending the internodes much earlier than pith parenchyma cells. The extension of cells in sub-apical region plays an important role in the longitudinal growth of tubers. In the first stages, the growth of tubers results from the change in the dimensions of cortical and pith parenchyma cells, due to the reproduction of apical meristem and later, mainly from the growth of the productive tissue in the pith parenchyma. Longitudinal growth is initially grater than the growth in diameter; however with shift in the position of vacuoles and their arrangement across rather than along the tubers, the growth pattern begins to change and lateral growth catches on and exceeds longitudinal growth. In fully grown tubers, pith parenchyma cells are larger than the cells in cortical parenchyma.
authors.affiliation: Azad Islamic University-Garmsar Branch, Garmsar, Iran.
authors.forename: Alireza
authors.initials: A
authors.lastname: Iranbakhsh
authors.forename: Mostafa
authors.initials: M
authors.lastname: Ebadi
authors.forename: Gholamreza Bakhshi
authors.initials: GB
authors.lastname: Khaniki
mesh_terms: D007492:Iran; D018519:Meristem / Q000254:growth & development*; D035281:Plant Tubers / Q000254:growth & development*; D011198:Solanum tuberosum / Q000254:growth & development*; D046509:Tissue Culture Techniques