Chapter 35

Cells make up tissues and tissues make up organs.

Plants have 3 main organs: Roots Stems Leaves

Used to anchor vascular plants

Absorbs minerals and water

Stores organic nutrients The main vertical root is

the taproot, which has branches called lateral roots

Root tips do most absorption

Tiny root hairs increase the surface area of the root

Stems have nodes (where leaves attach) and internodes (in between leaves)

Shoots form from axillary buds that grow from where leaves attach to stems

Modified stems include: rhizomes (ginger or garlic), tubers (potatoes), bulbs (onions)

Leaves are where sunlight is absorbed by chlorophyll for photosynthesis

Consist of a blade and a stalk (petiole)

Veins are the vascular tissue (xylem and phloem)

Modified leaves include tendrils, spines, bracts (poinsettia), and cacti storage leaves.

Stomata are openings in leaves for gas exchange Guard cells control whether stomata are open or

closed Mesophyll is the tissue where photosynthesis occurs Xylem and phloem are in the mesophyll, and are

enclosed by bundle sheath cells

Dermal: outer protective covering; includes cuticle, a waxy coating that prevents water loss

Vascular: xylem and phloem Ground: used for storage, called pith or

cortex

Parenchyma Cells: “typical plant cells”

Collenchyma Cells: support young parts of plant shoots

Sclerenchyma Cells: Mature cells, functionally dead, used for support

Meristems generate cells for new organs Plants grow throughout their lives, but do

die: Annuals: complete their life cycles in a year

or less; grains, beans, wildflowers Biennials: live 2 years; beets, carrots Perennials: live many years: trees, shrubs,

grasses

Roots and shoots grow from the tips (apical meristems)

The root tip is covered by the root cap (protection)

Zone of cell division: where mitosis occurs

Zone of elongation: root cells elongate

Zone of maturation: cells differentiate and become mature

Tissues called vascular cambium and cork cambium produces secondary xylem and phloem which turns into wood

Rings of trees build up as trees age. The center is called heartwood; outer layers are called sapwood.

Bark is used for protection and has phloem in it