Straight root system, spindle-shaped main root, buried about 2m deep, and root groups are mostly concentrated in 0 ~ 30 cm soil layer.

2. Stem

The stem is erect, with many branches on the upper part, often purplish red; Plant height150 ~ 300 cm, smooth or slightly hairy stems, thick stems1~ 2 cm, even up to 3cm.

3. Leaves

Leaves vary greatly with different growth stages, and the lower part is rooted and leaves, which are clustered, with large leaves, length10 ~ 30 (50) cm, width 2 ~ 8 cm, and no obvious petiole. Leaves alternate, different in shape, lanceolate or ovate, usually pinnately lobed, stem leaves are small, with stems at the base, long10 ~ 25 cm, and covered with white powder on both sides.

4. flowers

There are many heads, which are arranged in a conical shape at the top of stems and branches; Involucre cylindrical, 7 ~ 9 mm long; Tongue-shaped flowers are pale yellow or white, and the tip of tongue has 5 teeth.

Step 5: Fruit

Achene is oval, about 6mm long, dark brown when mature, squashed, with/kloc-0 longitudinal rib per mask and short beak; There is a bundle of white crown hairs degenerated from calyx. The seeds are small and light, with 1000-grain weight1.0 ~1.5g, and about 1kg seeds100000 ~1500000.

The cardinal number of cell chromosomes in Lettuce is x=9. Therefore, the lettuce is a diploid plant with the cell chromosome number 2n= 18.

Lettuce