Topic 13

Plant Science

13.1.1 Compare the 4 main types of plants by External

Plant Structures• Bryophytes (mosses)

– No roots, but rhizoids– Mosses = simple leaves & stem– Liverworts = flattened thallus– Max height = 0.5 meters– Reproduction = spores in a capsule

at end of stalk

• Filicinophytes (ferns)– True roots, leaves, short non-woody stem

• Leaves are pinnate = in pairs of leaflets– Max height = 15 meters– Reproduction = spores in sporangia under

leaves

• Coniferophytes (conifers)– Shrubs or trees with roots, leaves, woody

stems. Leaves are narrow with thick waxy cuticle

– Maximum height = 100 meters– Reproduction = seeds in female cones.

Male cones produce pollen

• Angiospermophytes (flowering plants)– Usually have roots, leaves and stems.

Stems may be woody or not.– Maximum height = 100 meters– Reproduction = seeds from flowers. Seeds

in fruits.

13.1.3 Plan diagram of stem

Plan diagram of root

Plan diagram of leaf

13.1.4 Explain the relationship between the distribution of tissues in the leaf and the

functions of these tissues.• Palisade mesophyll - main

photosynthetic tissue– Near surface where the light is most

intense for photosynthesis• Upper epidermis

– Upper surface protects internal structure of leaf from water loss.

• Stoma - a pore/opening gas moves through– In lower surface - the barrier between leaf and

atmosphere• Spongy mesophyll - main gas exchange surface

– Near stomata in lower surface for easy gas exchange• Guard cells

– A pair cells located on sides of stoma to open or close them

• Xylem - Carry water from roots to other parts of plant

• Phloem - Carry products of photosynthesis (glucose = food for plant)

• Both are a vein that runs through center of leaf so all cells are near for exchange of materials

13.1.5 Outline the adaptations of xerophytes

– CAM and C4 physiology (Crassulacean acid metabolism)(phosphoenol pyruvic acid (C3) to form Oxoloacetic acid (C4)

• Involves opening stomata during night, not day

– Reduced leaves• Reduced surface area = reduced transpiration

– Rolled leaves• Protected surface area = reduced transpiration

– Thickened waxy cuticle• Keeps water in

• reduced number of stomata– Fewer openings for water to escape

• stomata in pits surrounded by "hairs”– Holds water in

• Spines– Reduces transpiration

• deep roots– Absorb water deep down in soil

• water storage tissue– Usable water during dry times

13.1.6 Outline two structural adaptations of hydrophytes.

• air spaces– Buoyancy = floating near surface

• Flotation– Allows plant to be at surface = light

• pliable parts with little strengthening tissue– Move with waves without breaking

• "breathing" roots– Roots sent above surface of water

• reduced roots– No need for roots = surrounded by water

• finely divided submerged leaves.– Surface area for water absorption