EFFECTS OF TEMPERATURE AND ELEVATED CO2 ON CELL-DIVISION IN SHOOT MERISTEMS - DIFFERENTIAL RESPONSES OF 2 NATURAL-POPULATIONS OF DACTYLIS-GLOMERATA L

The aim was to establish whether temperature and/or elevated [CO2] (si milar to 700 mu mol mol(-1)) affects the cell doubling time (cdt) in t he different zones of the shoot apex of two natural populations of Dac tylis glomerata originating in Portugal (38 degrees 53' N) and in Swed en (63 degrees 09' N). In the Portuguese population at ambient [CO2], only the pith rib meristem (PRM) exhibited a significant shortening of cdts from 10 to 30 degrees C, Elevated [CO2] resulted in a significan t shortening of cdt, particularly in the PRM where cdt was reduced 4 . 8- and 6 . 1-fold at 10 and 20 degrees C, respectively, but only 2-fo ld at 30 degrees C, In the Swedish population at ambient [CO2], there were no consistent temperature-dependent alterations to cdt and this p opulation was less responsive to elevated [CO2] than the Portuguese po pulation, Nevertheless, elevated [CO2] resulted in a significant short ening of the cdt for some of the zones; the maximum reduction occurred in the PRM at 30 degrees C. We concluded that in the shoot apex of th e Portuguese population, and most notably in the PRM, 10 and 20 degree s C were non-optimal temperatures for cell division, whilst the Swedis h population was relatively buffered against temperature change, Eleva ted [CO2] resulted in substantially greater reductions in cdts in the shoot meristem of the Portuguese population than in that of the Swedis h population.