15th International Conference on Arabidopsis Research - TAIR

T13-019
DIURNAL CHANGES IN CYTOKININ LEVELS IN
ARABIDOPSIS PLANTS
Hoyerová K(1), Kamínek M.(1)
1-Institute of Experimental Botany ASCR, Rozvojová 135, CZ-16502 Prague 6, Czech Republic
Changes of cytokinin/auxin ratio are decisive for induction of specific
developmental processes in plant cells. Cytokinin levels with respect to auxin
in aerial parts of plants can be affected by diurnal changes in rates of their
biosynthesis and metabolism and also by the rate of their import from roots
which represent the main site of cytokinin biosynthesis. The rate of cytokinin
transport to shoots via xylem sap flow is influenced by environmental factors
affecting transpiration namely by light and temperature. The aim of our
research has been to determine the changes in cytokinin levels during the
day/night cycle.
Plants (Arabidopsis thaliana L. Columbia) were grown in hydroponics under
16h/8h day light) at 25 oC. Cultivation of plants under two different levels
of relative air humidity (60% and 90%) allowed us to determine the effect
of transpiration on cytokinin levels in aerial organs during the day/night
cycle. Another set of plants was grown under green house condition in
soil. 55 days old plants were harvested in 3 h intervals during one day/night
cycle. Cytokinins were extracted separately from different plant organs
using dual-mode solid phase extraction (Dobrev 2002) and determined by
HPLC/MSn. Sixteen different cytokinin bases, ribosides and glucosides and
four different cytokinin ribotides were identified and determined. Formation
of isopentenyl-7-glucoside appeared to be the main way of down-regulation
of physiologically active cytokinins in response to the temporal accumulation
isoprenoid cytokinins. The importance of the day/night period for sampling of
plant material for cytokinin analysis, effects of air humidity on cytokinin levels
and differences in cytokinins in different plant organs will be discussed.
References: Dobrev P., Kamínek M.: Fast and efficient separation of cytokinins
from auxin and abscisic acid and their purification using mixed-mode
solid-phase extraction, Journal of Chromatography A, 950 (2002) 21-29.
Acknowledgements: Supported by the Grant Agency of the Czech Republic (grant No.
206/02/0967).
T13 Others
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin