Botany Stems

Woody Twigs Vocabulary Alternate-leaves spiral around stem Opposite –leaves arranged in pairs Whorled-leaves arranged in groups of three or more

Leaf Terms Internode-distance between nodes Blade-flat leaf part

Stem Terms petiole-leaf stalk Bud-can become branch, flower or scale Terminal bud-at top of twig

More Stem Terms Bud scale scar-count to tell how old a twig is Stipules-paired appendages Deciduous-lose leaves annually Leaf scar- left after leaf falls off Bundle scar-location of xylem and phloem, characteristic for particular plants

Stem Origin and Development Apical Meristem – At tip of stem Where cells divide Makes stem longer

Primordia Tiny embryonic leaves Develop into mature leaves

Three Primary Meristems Protoderm-outer layer becomes epidermis and is covered with a waxy , protective layer Procambium-interior of protoderm, makes xylem and phloem Ground meristem-makes p[arenchyma

Pith Made of parenchyma Large cells Breaks down after formed Leaves hollow area

Cortex Extensive Replaced by tissues from within Function in storage

Vascular Cambium Narrow band of cells Becomes secondary tissues Increases girth

Cork Arises within cortex Called cork cambium Made from cork cambium Becomes filled with suberin Cells die Makes up outer bark Reduces water loss Protects against mechanical injury

Lenticels Pores for gas exchange in stems Spaces between cells Fissures in the bark of older trees