168 – II.3. BRASSICA CROPS (BRASSICA SPP.)
Growth stages of annual B. napus plant development are illustrated in Figure 3.20.
The glaucous lower leaves form a rosette from which the flowering stalk emerges bearing
a dominant, indeterminate main raceme. The upper stem leaves are small, lanceolate,
sessile and clasping. Plants of the species B. napus, B. rapa and B. juncea can be
distinguished by their upper leaf attachment to the stem as illustrated in Figure 3.21.
Flowering begins with the lowest bud on the main raceme and continues upward with
three to five or more flowers opening per day. The buds, unlike those of B. rapa, are held
above the uppermost open flowers. Flowers on the secondary branches begin to open
about three days after the opening of the first flowers on the main raceme. The siliques
are ascending on slender pedicles and about 7-10 cm long with a beak about 1.3 cm long.
Seeds are dark brown to black, and weigh 2.5-5.5 g per 1 000 seeds.
Figure 3.20. Growth stages of B. napus var. napus f. annua
Figure 3.21. Upper leaves of B. rapa, B. napus and B. juncea
Notes: a) Seedling cotyledons; b) cotyledons and
first true leaf; c) rosette; d) flowering;
e) pod set; f) mature plant.
Notes: a) B. rapa, fully clasping stem;
b) B. napus partially clasping;
c) B. juncea, non-clasping.
Source: Downey (1983). Courtesy AAFC Reseach Station, Saskatoon (Photographer R.E. Underhood).
Brassica juncea
B. juncea vegetables
In China and south-east Asia many vegetable forms of B. juncea have been developed
and classified as species or subspecies under numerous names, depending on the
morphological features given the greatest importance. Kumazawa and Able (1955)
examined some 200 East Asian cultivars of B. juncea vegetables grown in China, Japan,
Nepal and Chinese Taipei on the basis of their plant size, root form, tillering and leaf
characteristics. All accessions of B. juncea and its subspecies were described as annuals
and placed in 25 different groups within 8 classes. These classes were further condensed
into four subspecies. The authors state that the subspecies evolved from the leafy and
oilseed forms of brown mustard, B. juncea (L.) Cross. From the collection, the authors
