J. Bonmort et G. Roblin, EFFECT OF 2,4-DICHLOROPHENOXYACETIC ACID ON THE DARK-INDUCED AND LIGHT-INDUCED PULVINAR MOVEMENTS IN CASSIA-FASCICULATA MICHX, Plant growth regulation, 19(1), 1996, pp. 61-65
2,4-dichlorophenoxyacetic (2,4-D) applied to excised leaves of Cassia
fasciculata modified the dark-induced (scotonasty) and light-induced (
photonasty) leaflet movements, showing that this compound acts on rapi
d turgor variation and the concomitant ion migrations, in particular K
+. 2,4-D inhibited the scotonastic closure in a dose-dependent manner
from 10(-8) M to 10(-5) M sind promoted the photonastic opening in the
same range of concentrations. The compound acted rapidly since a trea
tment as short as 5 min gave an obvious effect on the motile reaction;
however, a lag period of 45-60 min was needed to observe its effect.
Although 2,4-D is a weak acid, its greatest physiological efficiency w
as obtained with pH values close to neutrality. The physiological resu
lts are discussed in relation to the chemical properties acid the char
acteristics of transport of the molecule.