206 – II.3. BRASSICA CROPS (BRASSICA SPP.)
Figure 3.37. Development stages of the Brassica napus zygotic embryo
Source: Courtesy Plant Biotechnology Institute, Saskatoon, Canada.
The size of seeds can be defined by both their physical dimensions and weight.
The range in seed weight among the Brassica crop species is given in Table 3.10. Typical
seeds of Brassica species and subspecies are illustrated in Figure 3.38. These drawings,
produced by the USDA many years ago, are still valid and can be used as a starting point
to distinguish many of the species and subspecies according to the reticulation patterns on
the seed surface. The different patterns are the result of variation in the size of the
palisade cells that form the outer cell layer of the seed coat.
Table 3.10. Typical seed weight ranges (or averages) of Brassica crop plants by species and form
Species Form g/1 000 seeds Source
B. napus Winter oilseed rape 4.5-5.5 Bengtsson et al. (1972)
Spring oilseed rape 2.5-4.6 Elliott, Franke and Rakow (2008)
B. rapa Winter turnip rape 3.0-4.0 Bengtsson et al. (1972)
Spring turnip rape 2.0-3.0 Bengtsson et al. (1972)
B. juncea Condiment and oilseed mustard* 2.5-3.0 Rakow and Rode (2009);
Rakow et al. (2009)
B. oleracea Cabbage 3.6 Ohio State University (2009)
Broccoli 2.7-5.8 Heather and Sieczka (1991)
Brussels sprouts 2.8 George (2009)
Kohlrabi 3.2 George (2009)
Note: * The Indian cultivar Pusa Bold has larger than normal seed at about 5.3 g/1 000.
Sources: Bengtsson et al. (1972; Elliott et al. (2008); Rakow and Rode (2009); Rakow et al. (2009); Ohio State
University (2009); Heather and Sieczka (1991); George (2009).
Vaughan and Whitehouse (1971) investigated and described the seed surface and
general features of some 200 Brassicaceous species including shape, colour, mucilage
production and hilum characteristics. Koul, Nagpal and Raina (2000) also examined the
seed surface architecture of 78 accessions from the 3 subtribes – Brassicinae, Raphaninae
and Moricandiinae – at both low magnification (x80) as well as the fine structure using a
scanning electron microscope (x640, x1260). They noted that the seed coat patterns at
high magnification were generally species-specific. However, significant seed coat
