AP BIOLOGY

Detailed explanation-1: -After primary growth is secondary growth. In secondary growth, the girth or width of the stem increases; it thickens. Secondary growth occurs in the secondary meristem, vascular cambium, or cork cambium. This layer gives the woody texture of the bark.

Detailed explanation-2: -The thickening of the stem that occurs in secondary growth is due to the formation of secondary phloem and secondary xylem by the vascular cambium, plus the action of cork cambium, which forms the tough outermost layer of the stem. The cells of the secondary xylem contain lignin, which provides hardiness and strength.

Detailed explanation-3: -The lateral meristem is responsible for the plants’ thickness. The increase in diameter of a plant’s stem and root is caused by cork cambium and vascular cambium. They can be found in dicot plants. These are the lateral meristems, which are in charge of the plant’s secondary growth.

Detailed explanation-4: -The vascular cambium is responsible for increasing the diameter of stems and roots and for forming woody tissue. The cork cambium produces some of the bark. In dicot stems, the vascular cambium initially differentiates from procambial cells within the vascular bundles (Fig. 1.8A).

Detailed explanation-5: -Primary growth occurs as a stem increases in length as a result of cell division in the shoot apical meristem. Secondary growth is characterized by an increase in thickness or girth of the plant, and is caused by cell division secondary meristems.