Canadian Journal of Botany, vol. 71, issue 8 (1993) pp. 1087-1092
Short-term effects of the plant growth retardant mefluidide on drought
resistance were investigated in seedlings of western red cedar (Thuja
plicata Donn), yellow cedar (Chamaecyparis nootkatensis D. Don),
and white spruce (Picea glauca (Moench) Voss). Mefluidide was applied
as a root drench at concentrations of 0, 0.1, and 0.4 mg cntdot L-1.
Following this, seedlings were stressed by withholding water for
a period of up to 7 days and then watering regularly thereafter.
Stomatal conductance of the mefluidide-treated seedlings decreased
significantly and remained lower than the control seedlings throughout
the stress period. As a result of the decreased conductance, shoot
water potentials in mefluidide-treated seedlings remained higher
throughout the stress period. There was a decrease in net photosynthesis
that was partially caused by stomatal limitations, the severity of
which depended upon the concentration of mefluidide applied. Mefluidide
treatment also resulted in an accumulation of abscisic acid in all
three species, and this may have been responsible for the effects
on stomatal conductance and water relations. In contrast, the mefluidide-treated
seedlings had the highest rates of photosynthesis after rewatering,
resulting primarily from a promotion of stomatal opening.
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