16.1.1     Draw a diagram to show the external parts of a named dicotyledonous plant including root, stem, leaf, sepal, stamen and carpel.

16.1.2     Draw plan diagrams to show the distribution of tissues in the stem, root and leaf of a generalised dicotyledonous plant.

Either one species could be selected for the whole study or different species could be used for stem, root and leaf - depending on the availability of local material and/or local interest. Note that plan diagrams show distribution of tissues (e.g., xylem, phloem) and do not show individual cells. They are sometimes called 'low power' diagrams.

LEAF

 

 

ROOT

 

 

STEM

 

16.1.3     Explain the relationship between the distribution of tissues in the leaf and their functions.

16.1.4     Outline four structural adaptations of xerophytes.

These could include: reduced leaves, Tolled leaves, spines, deep roots, thickened waxy cuticle, reduced number of stomata, stomata in pits surrounded by 'hairs', water storage tissue, low growth form, reduced life cycles.

 16.1.5     Outline two structural adaptations of hydrophytes.

These could include air spaces, floatation, pliable parts with little strengthening tissue, 'breathing' roots, reduced roots, finely divided submerged leaves.

16.1.4 and 16.1-5 illustrate the Theme 'Structure and Functions'.

16.2.1     Define water potential.

16.2.2     State that water moves down a water potential gradient (cross reference

Note that water potential terminology is not required, only the principle that water moves from a region of higher water potential to a region of lower water potential. Calculations involving water potential will also not be required.

 16.2.3     Describe the process of mineral ions uptake into roots by active transport.

16.2.4     Explain how the root system provides a large surface area for mineral ion and water uptake by means of branching, root hairs and cortex cell walls.

16.2.5     Explain the process of water uptake in roots by osmosis.

16.2.6     State that terrestrial plants support themselves by means of cell turgor and xylem.

Turgor should be limited to the idea that differences in water potential create pressures inside plant cells owing to the rigidity of the cellulose cell walls.

 16-2.7     Define transpiration.

16.2.8     Explain how water is carried by the transpiration stream including an outline structure of xylem vessels, transpiration pull, cohesion and evaporation.

16.2.9     Explain how the abiotic factors light, temperature, wind and humidity affect the rate of transpiration in a typical terrestrial mesophytic plant.

More than a description is required.

16.2.10     Define translocation.

16.2.11     Outline the role of phloem in active translocation of various biochemicals.

Detail explanations of all the hypotheses that account for translocation are not required. Outlined structure of sieve tubes, the role of companion cells in generating energy from respiration. Mention that sieve tubes can carry material in either direction, at variable rates. Knowledge of experimental evidence leading to hypotheses is not required.

 16.2.12     Describe an example of food storage in a plant.

16.2.13     Outline the gas exchange pathways in the root and leaf of a typical terrestrial mesophytic plant.

16.3.1    Draw the external and internal structure of a named dicotyledonous seed.

16.3.2     Describe the metabolic events of germination in a typical starchy seed.

Absorption of water precedes the formation of gibberellin in the cotyledon. This stimulates the production of amylase which catalyses breakdown of starch to maltose which subsequently diffuses to the embryo for energy production and growth. This can be compared with the malting of barley grains in the brewing industry. The enzyme catalysed metabolic processes could be studied alongside laboratory investigations.

 16.3.3     Explain the conditions needed for the germination of a typical seed.

16.4.1     Outline the importance of plants to people in terms of food, fuel, clothing, building materials and aesthetic value.

16.4.2     State one example of a plant in each of the five categories above.

16.4.3     Describe the cultivation of a plant of economic importance.

16.4.4     Discuss two techniques used in cultivation which have had led to improvement in yield (cross reference 10.6).

The teacher may select according to interest from: traditional plant genetics and hybridisation and transgenic techniques. Tissue culture (micropropagation) is a technique for making available plants with an identical genotype (e.g., F₁ hybrids). Leaf cell protoplasts can be also used in somatic hybridisation.