Ja. Wilmer et al., EFFECTS OF ABSCISIC-ACID AND TEMPERATURE ON ERUCIC-ACID ACCUMULATION IN OILSEED RAPE (BRASSICA-NAPUS L), Journal of plant physiology, 150(4), 1997, pp. 414-419
The qualitative effect of growth temperature on the level of erucic ac
id (22:1) is similar in seeds and microspore-derived embryos (MDEs) of
oilseed rape, as we have previously shown (Wilmer et al., 1996), but
absolute levels of 22:1 are lower in MDEs. In this paper we studied wh
ether this temperature effect is mediated by changes in the level of o
r sensitivity to abscisic acid (ABA). For this purpose we measured end
ogenous levels of ABA in developing seeds and MDEs. In addition, 22:1
accumulation was determined in MDEs exposed to a range of concentratio
ns of ABA. The endogenous level of ABA in seeds, about 5 to 10 nmol/g
FW, was twentyfold higher than the concentration at which maximum sens
itivity in MDEs occurred. Further evaluation using dose-response curve
s showed that at both 15 and 25 degrees C the half-maximum increase in
22:1 level in MDEs was observed at about 0.3 mu mol/L ABA, though thr
oughout the concentration range tested levels of 22:1 were about 10 mo
l% higher at 15 degrees C than at 25 degrees C. This indicates that th
e sensitivity to ABA remains the same in this temperature range. Indep
endent from the temperature effect, exogenously applied ABA induces an
increase of about 10 mol % in 22:1 within the range of 10 to 25 degre
es C. In addition to this effect on 22:1 level, ABA stimulates the pro
duction of triglycerides in MDEs, whereas temperature has no effect on
oil accumulation. In combination, our data indicate that growth tempe
rature and ABA are independent and additive stimuli in regulating the
level of 22:1 in oilseed rape.