An-Najah Staff

The circadian clock is an important timing system that controls
physiological responses to abiotic stresses in plants.
However, there is little information on the effects of the clock
on stress adaptation in important crops, like barley. In addition,
we do not know how osmotic stress perceived at the
roots affect the shoot circadian clock. Barley genotypes, carrying
natural variation at the photoperiod response and clock
genes Ppd-H1 and HvELF3, were grown under control and
osmotic stress conditions to record changes in the diurnal
expression of clock and stress-response genes and in physiological
traits. Variation at HvELF3 affected the expression
phase and shape of clock and stress-response genes, while
variation at Ppd-H1 only affected the expression levels of
stress genes. Osmotic stress up-regulated expression of clock
and stress-response genes and advanced their expression
peaks. Clock genes controlled the expression of stressresponse
genes, but had minor effects on gas exchange and
leaf transpiration. This study demonstrated that osmotic
stress at the barley root altered clock gene expression in the
shoot and acted as a spatial input signal into the clock. Unlike
in Arabidopsis, barley primary assimilation was less controlled
by the clock and more responsive to environmental
perturbations, such as osmotic stress.