Plant Structure: Organs

1. Plant Structure: Organs • Organs composed of 1 or more tissues • Plant organs • 3 major types: • roots • stems • leaves • Flowers and fruits evolved from stems and leaves

2. Plant Structure: Roots • 4 zones of growing root • Rootcap: protect tip of root; secretes lubricant • Root structure • Celldivision: apical meristem; production of new cells • Cellelongation: expansion of cells due to enlarging vacuole • Cellmaturation: specialization of cells • root hairs • storage • vascular tissue

3. Most water absorbed by root hairs Plant Structure: Roots • Uptake of water and nutrients • Main functions of roots • Anchor and support • Water and nutrient uptake • Root hairs are projections of epidermal cells • Substantially increase surface area of roots

4. Plant Structure: Roots • Fibrous, multibranched roots (e.g. lettuce) • Dominant tap root • Root types • Tap roots used to absorb water deep in soil • Some tap roots used to store carbohydrates (e.g. carrots) • Adventitious roots • root-like structures arising from stems or leaves • e.g. prop roots (e.g. corn) and holdfasts (e.g. poison ivy) • Tuberous roots • Swollen structure on fibrous root used to store carbohydrates (e.g. sweet potato)

5. Stem Structure Plant Structure: Stems • Nodes: location of leaves on stem • Stems • Internodes: stem between leaves • Buds: undeveloped leaves or flowers • Terminal (apical) • axillary (lateral) • Apical dominance is growth inhibition caused by apical bud

6. Plant Structure: Stems • Functions • Support leaves, flowers, fruits • Stems • Transport of water (xylem) and products of photosynthesis (phloem) • Storage of carbohydrates • Tubers = swollen underground stems that store carbohydrates (e.g. potato; eyes are axillary buds) • Corm = swollen base of stem covered in papery leaves ( e.g. crocus) • Bulb = cluster of fleshy leaves attached to short, thick stem with basal roots (e.g. onion) • Bulbils = tiny bulbs arising in leaf axils (e.g. lily) • Rhizome = horizontal stem below ground that produces roots and shoots at each node ( e.g. iris, ferns)

7. Plant Structure: Stems • Examples of stems modified for storage • Stems

8. Plant Structure: Stems • Stems used only for asexual reproduction • Stolon (or runner) = horizontal stem that arises from leaf axil and runs above ground (e.g. strawberry, spider plant) • Stems • When tip of stolon hits ground a new plant forms

9. Sucker = stem arising from root tissue, often from cut woody plant Plant Structure: Stems • Other types of modified stems • Spur = stem with short internodes growing from a larger branch of woody plant • Stems • Waterspout = stem that arises from latent buds in branches of woody plants

10. Plant Structure: Stems • Other types of modified stems • tendrils = twining stems used to secure climbing plants to vertical surfaces (e.g. peas, grapes) • Stems • prickles = tiny, pointed projections of epidermis tissues of stems (e.g. blackberry) • thorns =long, pointed projections produced in leaf axils (e.g. Hawthorn) • cladophylls =stems modified for photosynthesis (e.g. cacti, asparagus)

11. Plant Structure: Stems • Examples of other modified stems • Stems