Plant Form and Function Plant organs Plant organs

Plant Form and Function Plant organs

Plant organs • Root system – roots • Shoot system – stem and leaves • Vegetative organs – (allow to live and grow): roots, leaves, stem • Reproduction: flowers, seeds and fruits

Roots • Underground, usually equal to shoot system in size • Anchors and gives support • Absorbs water and minerals • Penetrates soil as it grows • Root hairs increase surface area • Produce hormones

Root organization • Root cap – apical meristem, replaced often • Zones • Cell division – primary meristem, mitosis • Elongation – cells lengthen and specialize • Maturation – root hairs, fully differentiated

Stems • Main axis of plant • Support leaves so that leaves are exposed to as much light as possible • Node – where leaf is attached • Internode – space between nodes • Vascular tissue used in transport • Can store nutrients and water and conduct photosynthesis

Leaves • • • Photosynthesis Size, shape and texture vary and is used in identification Blade – wide portion of leaf Petiole – stalk, attaches blade to stem Axillary bud – where branch or flower may originate

Leaf anatomy

Plant tissues • Meristematic tissue = embryonic • Apical meristem – located on tip of stem and roots, primary growth • Lateral meristems – secondary growth • Woody (non herbaceous), non woody (herbaceous – perennial, dies back in winter)

Woody Stems • Primary (length) and secondary (girth of trunks) tissues • Secondary tissues form from lateral meristem: • vascular cambium – produces secondary xylem (wood) • Vascular cambium produces new xylem and phloem each year • cork cambium – produces a tough covering that replaces epidermis early in secondary growth • 3 distinct areas: • Bark – all tissues outside the vascular cambium, living part of tree • Contains phloem, can kill a tree if damaged • Wood – xylem, almost all is dead when it functions • Cork

Secondary growth of trees

Vascular tissue • Xylem – water and minerals, roots to leaves • Phloem – sucrose and organic molecules (hormones) form leaves to roots • Complex tissues – contain 2 or more kinds of cells • Both extend from roots to leaves • Roots- located in vascular cylinder, stem – vascular bundles, leave – leaf veins

Vascular tissue