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