Plant Growth

Meristem and Growth

• Meristem tissues are perpetually embryonic tissues in plants.

• Apical meristems are located at the tips of roots and shoots, and in the buds. They are responsible for lengthening of primary growth

• Lateral meristems are cylinders along the entire length of the plant. They are responsible for changes in width or girth of secondary growth.

Herbaceous Plants

• Herbaceous plants are non-woody plants that mainly rely on primary growth.

• They are more likely annuals that complete their life cycle in on year.

Woody Plants

• Woody plants are perennials that rely on both primary and secondary growth for or more than two growing seasons

• Woody growth helps support the plant in it efforts to reach the sun while also providing protection, insulation, and waterproofing

Vascular Cambium

• The site of secondary growth is the vascular cambium and the cork cambium

• The vascular cambium gives rise to secondary vascular tissues, while the cork cambium replaces epidermis with periderm (bark)

Secondary Growth

• Vascular Cambium cells divide and specialize into secondary xylem on the inside and secondary phloem on the outside

• The also generate new vascular cambium laterally as the girth of the tree increases

Cross Section of Wood

• Heart wood in the center is composed of non-functioning xylem (strong, waste)

• Sapwood to the outside (soft, functioning)

• Bark is composed of cork, cork cambium, and secondary phloem

Seasonal Xylem Growth

• Early wood grown in during moist conditions form cells that are large in diameter

• Late wood grown in dry periods form cells that are smaller in diameter

Dendrology

• Successive seasonal changes in moisture produce yearly growth rings in temperate climates. Such patterns can be used to determine the age of the tree