**2. Biology**

The stem of oilseed rape is 100–180 cm in height. It is branched and covered with a waxy coating. The number of branches depends on the crop density. In the dense crops, 6–7 lateral branches are formed, and in the rarer ones, there are up to 20 branches. Oilseed rape leaves are green with a bluish tint, and covered with a waxy layer. The lower leaves, with stalks, lobed and curly, and the upper ones are

#### *Oilseed Rape: Biology, Use, Current Cultivation Issues and Agronomic Management DOI: http://dx.doi.org/10.5772/intechopen.109180*

lanceolate, without petioles. The rosette leaves turn yellow and fall before the formation of inflorescences [1, 6–8].

The colour of the oilseed rape flower is light yellow. It blooms for an average of 3 days. Flowers are arranged on racemes. Lateral racemes are located next to the apical raceme. Oilseed rape is a self-pollinating plant, so bees are not necessary for pollination. However, it has been found that oilseed rape that is visited by bees produces a higher seed yield, sets seeds faster, and matures them more consistently. The fruit is a 4–6 mm wide and 3–10 cm long self-opening pod with round seeds of various colour: brownish, brown, black, grey-black and yellowish. The type of oilseed rape root system is a taproot. Its main root penetrates the soil up to three meters deep. Lateral roots branch off in the upper part of the main root [3, 6, 9].

Several types of this plant were developed after its introduction to Europe. According to the nature of vegetation, oilseed rape includes spring (annual) and winter (biennial) subspecies. The botanical characteristics of spring and winter oilseed rape are similar. However, both forms have some distinctive features. The growth stages of spring and winter oilseed rape correspond, but they differ in duration [1, 3, 10].

The overall life cycle of oilseed rape includes a list of different growth stages: seed germination, seedling formation, leaf formation, stem growth, budding, flowering, pod development, seed maturation and stem drying (**Figure 1**) [8, 11].

Spring oilseed rape is sown in the spring, and stem development begins immediately after germination. The rosette is formed at higher temperatures under long day conditions. This stage of oilseed rape development lasts 30–40 days. The stem growth takes 8–10 days. The mass of roots of the spring-type oilseed rape is lower than that of the winter type. Larger lateral root branches of spring oilseed rape are found at 25–45 cm depth. Spring-type plants form 20–50 flowers in the apical raceme. Blossom spreads gradually from top to bottom in the inflorescence [12–14].

Winter oilseed rape is the original form of Brassica napus. It requires vernalisation which promotes flowering. One of the distinctive features of winter oilseed rape is the cessation of vegetation in winter and the renewal of vegetation in spring. The vegetation period of winter rape is 130–180 days. The total duration of oilseed rape growth is 270–320 days. It is sown in autumn and forms a rosette of 5–10 leaves on a short stem that remains in the soil surface during winter. The terminal bud of the rosette is raised above the soil surface by 2–3 cm [7, 11].

The intensive plant vegetation renews in the following spring. The growth of the long vertical stem and formation of 2–8 new leaves of the rosette begins when the average temperature reaches 2–9°C heat. In the stage of stem extension, the height of the plant increases rapidly, and the branching of the plant begins. Inflorescences

#### **Figure 1.**

*Growth stages of oilseed rape life cycle: 1 - germination and emergence; 2 - leaf development; 3 - side-shoot formation; 4 - stem elongation/extension; 5 - inflorescence/flower-bud emergence; 6 – Flowering; 7 - pod/seed development and ripening; 8 – Senescence [8].*

begin to form 15 days after the beginning of vegetation. The top of the stem is covered with leaves, and green inflorescences of tightly packed buds are situated between them. Winter-type plants form from 20 to 90 flowers in the apical raceme. The flowers of winter oilseed rape begin to blossom in the raceme from the bottom towards the top in the late spring. This period lasts 25–30 days. It is followed by the development of lateral branches. The total number of pods formed in winter and spring oilseed rape differs. It is higher in winter-type oilseed rape than in the spring type. The quantity of pods per plant in winter oilseed rape is from 200 to 500; in spring oilseed rape, it is from 80 to 200 pods. The average number of seeds per pod is 18-35. The average weight of 1000 seeds of winter rape is about 4–6 g [3, 6, 8, 14].
