Oilseed rape has a tap root system supporting a well-branched
stem (0.5-2m tall). Axillary branches and the main stem terminate in racemes which bear yellow
flowers and photosynthetic dark green, lyrate leaves. The stems and pods are photosynthetic during
pre- and post-flowering events respectively. During development of the racemes and after their
flowering, the stems senesce rapidly (Tayo and Morgan, 1975; Bilsborrow, 1985) to leave a
virtually naked stem to sustain the maturing pods.
In oilseed rape, flowering initiates at the main terminal raceme and progresses towards the primary branches. Flowering also depends on their branch position, as those at the base of branches open first, then open progressively towards the tips.
Nutrient competition from the earlier set, lower pods results in the abortion of the youngest
pods, flowers and buds. This mechanism therefore enables the plant to limit its pod production
to a level it can support. The pod canopy is another factor that shows plasticity during the
early months as the plant is in an indeterminate state (ie. retaining its ability to stimulate
new reproductive racemes). For example, following severe lodging new racemes can be initiated
to produce fertile pods, but unfortunately this increases the distribution
of pod maturation and is therefore agronomically undesirable (Daniels et al, 1986).
