Plants-stems

Question 1

Functions

Answer 1

Connect leaves and roots via vascular tissue allowing transport of materials

Support and elevate leaves and flowers to improve photosynthesis and pollination

Some specialized for storage of water and carbohydrates

Some perform photosynthesis

Protection from herbivores

Question 2

Structure

Answer 2

May be HERBACEOUS (soft, pliable, photosynthetic) or WOOD (contain wood, are hard, have bark, non-photosynthetic) – all gymnosperms are wood

VASCULAR BUNDLE – long strands of xylem (nearer centre) and phloem that run from the roots to the leaves (bundles are scattered in monocot, and in ring-like formation in dicot)

VASCULAR CAMBIUM – layer of meristematic cells that divides to produce new xylem and phloem cells each year (allows wood trees to become thicker over time) – layer between xylem and phloem

Question 3

Wood stem structure only

Answer 3

• WOOD” – made of young xylem that transports water and nutrients (SAPWOOD), and older xylem that is filled with resins and oils and no longer transports water (HEARTWOOD – centre)
• BARK – outermost layer of wood plants (includes phloem, cork cambium and cork) that helps protect against herbivores, dehydration, and sometimes fire
• CORK CAMBIUM – layer of meristematic tissue that produces the tough, outer layer (CORK) of the tree that prevents water loss
• GROWTH RINGS – each ring consists of light wood (formed rapidly in spring, usually lighter and wider) and dark wood (formed in summer, usually darker and narrower)

Question 4

Specializations

Answer 4

• *Not all stems hold plants upright – some grow underground, some modified for food and water storage, some are used for reproduction**
• STOLONS – grow along the soil (horizontal), and can produce new plants at nodes (e.g. spider plant)
• RHIZOME – underground, horizontal(e.g. ginger)
• TUBERS– underground, swollen rhizome, used for storage (e.g. potato)
• CORM – short,swollen, underground, vertical, used for storage

Question 5

Human uses

Answer 5

• Fuel(wood, ethanol)
• Food – sugar cane, potatoes, maple syrup, asparagus, cinnamon
• Medicines – aspirin from willow bark, opiates from poppies, anti-cancer drug from yews
• Textiles (fabric) – linen, hemp, bamboo
• Chemicals – turpentine, latex rubber
• Wood based products – furniture, paper