13.1.5 Secondary Growth: Lateral Meristems and Secondary Vascular Tissue

Question 1

Secondary Growth: Lateral Meristems and Secondary Vascular Tissue

Answer 1

• Both monocots and dicots can sprout lateral roots that arise from the pericycle.
• Dicot stems contain vascular cambium (a lateral meristem) that allows for secondary growth. Secondary growth is growth resulting in an increase in girth.
• Major developments during secondary growth include: the formation of secondary vascular tissue (new xylem and phloem), the formation of vascular rays, and the formation of periderm (cork cambium and cork).
• The rings used to count the age of a tree reflect the seasonal growth of new xylem.

Question 2

pericycle

Answer 2

• The pericycle of a root, the outermost layer of the stele, can become meristematic and give rise to lateral roots. The stele of a lateral root connects to the stele of the main root, allowing the vascular tissue to be continuous with the main root.

Question 3

vascular cambium

Answer 3

• The meristematic tissue called vascular cambium is found between the xylem and phloem of the vascular bundles of a dicot stem. The vascular cambium is a lateral meristem that allows for secondary growthin the dicot stem by producing secondary xylem and phloem.

Question 4

note

Answer 4

• In the young part of the stem, secondary growth has not occurred. The stem consists of a central pith, xylem tissue, vascular cambium, phloem, and epidermis.
• During secondary growth of the stem, the vascular cambium forms new xylem and phloem. Also, vascular rays develop that function in the radial transport of water. Cork cambium eventually arises from parenchyma cellsin the cortex of the stem. The cork cambium produces cork, which serves as a protective covering that replaces lost epidermis. The cork cambium and cork are collectively referred to as periderm.
• The rings in trees reflect the seasonal growth of secondary vascular xylem. During the winter, the vascular cambium becomes dormant. As growth resumes in the spring, the vessel elements and tracheids of the xylem are relatively large, for the transport of large amounts of water. As spring progresses into summer, the vessel elements and tracheids become smaller as seen in the light micrograph to the left.

Question 5

The two lateral meristems responsible for secondary growth are

Answer 5

• vascular cambium and cork cambium.

Question 6

The cork cambium and the tissues that it produces together are called

Answer 6

• periderm

Question 7

Which statement regarding xylem growth is correct?

Answer 7

• The vascular cambium produces xylem toward the inside of the stem.

Question 8

Which label corresponds to the phloem on this young dicot stem?

Answer 8

• label C

Question 9

Thickening of roots and stems takes place because of activity at the

Answer 9

• vascular cambium.

Question 10

Which label corresponds to the vascular cambium of this young dicot stem?

Answer 10

• label D