Developmental and Structural Section
Dubrovsky, Joseph , Shishkova, Svetlana .
Determinate root growth in Cactaceae and problem of meristem maintenance.
All plant roots have indeterminate phase of growth when the root apical meristem (RAM) continuously produces new cells. In a number of plant taxa, this growth phase is followed by the phase of determinate root growth. The main feature of this phase is complete meristem exhaustion and differentiation of all ex-meristematic cells. The determinate growth is described in lateral roots of various species from different taxa. It is already 10 years since we found a unique situation in Sonoran Desert Cactaceae in which a primary root is programmed to complete meristem consumption. In some species it takes place during only 2 or 3 days. We have shown that during RAM exhaustion meristematic cells continue proliferation, but eventually all RAM cells differentiate. Moreover, no signs of program cells death are found within the RAM. Post-germination, depending on species, initial cells within the RAM are not activated after germination or if activated have a very limited activity; the quiescent center is not established at all or established only for a few days. These data demonstrate that without the quiescent center an indeterminate root growth can not be maintained. This implies that previously proposed models of meristem maintenance [based on considerations that (a) the quiescent center functions as a pool of non-differentiated (stem) cells; (b) the derivatives of the quiescent center are displaced into the RAM, and (c) meristematic cells have few cell division cycles within the RAM and then are displaced into transition zone] are valid. We will present also the data that show that determinate developmental program is stable in the studied species and will discuss ecological significance of this type of growth for desert Cactaceae.
We thank S. Napsucialy-Mendivil for excellent technical help and DGAPA-PAPIIT, UNAM (project IN227206) for financial support.
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1 - Instituto de Biotecnología, Universidad Nacional Autónoma de, Departmento De Biología Molecular de Plantas, Apdo. Postal 510-3, Cuernavaca, Morelos, 62250, Mexico
root apical meristem
Presentation Type: Oral Paper:Papers for Sections
Location: PDR 2/Hilton
Date: Monday, July 9th, 2007
Time: 8:30 AM