SBI 3UW Topic 9: Plant Biology

Use both BCC (Biology Course Companion) and CB (Campbell Biology PDFs located on Mr. Busch and Mrs. Drung’s websites) to complete the assignment outlined. Use the headings provided to organize your notes, and review the IB syllabus (posted on the websites) for the requirements according to IB. Some of the applications and skills will be executed in the fall; problems and questions with the material will also be addressed at that time. Following this, there will be a unit test. The notes you make this summer will be your notes for this material. No new notes will be made in class.

9.1Transport in the Xylem of Plants

Understandings:

  • Transpiration is the inevitable consequence of gas exchange in the leaf.

Read CB ‘The Control of Transpiration’ pg. 759-761.

Use pg.404 BCC and summarize the information under this heading.

  • Plants transport water from the roots to the leaves to replace losses from transpiration.

Draw Fig. 11 pg. 409 BCC and discuss the transport of water shown in the diagram.

  • The cohesive property of water and the structure of the xylem vessels allow transport under tension.

Read CB ‘Transport of Xylem Sap’ pg. 756-759.

Use BCC pg. 406-407 and summarize the information under this heading.

Answer Data-based questions: The Renner experiment on BCC pg. 407.

  • The adhesive property of water and evaporation generate tension forces in leaf cell walls.

Use BCC pg. 407-408 and summarize the information under this heading.

  • Active uptake of mineral ions in the roots causes absorption of water by osmosis.

Read CB ‘Absorption of Water and Minerals by Roots’ pg. 754-756.

Use BCC pg. 408 and summarize the information under this heading.

Answer Data-based questions: Fungal hyphae and mineral ion absorption on BCC pg. 408.

Applications and skills:

  • Application: Adaptations of plants in deserts and in saline soils for water conservation.

Read CB ‘Xerophytes have evolutionary adaptations that reduce transpiration’ pg.762 and BCC ‘Adaptations for water conservation’ pg. 409-410 and make a note combining the information to explain how plants adapt to low water and high saline environments for water conservation.

  • Application: Models of water transport in xylem using simple apparatus including blotting or filter paper, porous pots and capillary tubing.

Write out the Nature of science statement taken from the syllabus.

Use BCC pg. 404-405 ‘Modelling water transport’ to describe how clay pots, capillary tubes and paper towel can be used to model water transport in xylem.

  • Skill: Drawing the structure of primary xylem vessels in sections of stems based on microscope images.

Draw and label the cross-section of a dicot stem shown in Fig.14 on pg. 411 of BCC.

Draw and label the longitudinal section of xylem vessels shown in Fig. 16 on pg. 411 of BCC.

Use BCC pg. 411 and summarize the information describing the structure of primary xylem and the formation of secondary xylem.

  • Skill: Measurement of transpiration rates using potometers. (Practical 7)

Read BCC pg. 405 ‘Using a potometer’

This will be performed in class in September.

  • Skill: Design of an experiment to test hypotheses about the effect of temperature or humidity on transpiration rates.

Read and answer the questions in BCC ‘Effect of humidity on transpiration’ on pg.405-406.

9.2 Transport in the phloem of plants

Understandings:

  • Plants transport organic compounds from sources to sinks.

Use CB ‘Translocation of Phloem Sap’ and ‘Phloem translocates its sap from sugar sources to sugar sinks’ on pg. 762-3, as well as BCC pg.412-13 make a note explaining the translocation of organic compounds from sources to sinks. Include in your notes a table of sources and sinks.

Answer the questions to the Activity in BCC pg.413.

  • Active transport is used to load organic compounds into phloem sieve tubes at the source.

Use CB ‘Phloem Loading and Unloading’ pg. 763 and BCC ‘Phloem Loading’ pg.413-14 to explain the loading of sucrose into sieve tubes. Be sure to include both the apoplastic and symplastic routes and the figures 3 and 4 in BCC in your answer.

Answer Data-based questions: Carbohydrates in cyclamen BCC pg. 414

  • High concentrations of solutes in the phloem at the source leads to water uptake by osmosis.
  • Raised hydrostatic pressure causes the contents of the phloem to flow towards sinks.
  • Incompressibility of water allows transport along hydrostatic pressure gradients.

Use CB ‘Pressure flow is the mechanism of translocation in angiosperms’ pg. 763-4 and BCCpg. 414-15 ‘Pressure and water potential differences play a role in translocation’ to explain the pressure flow hypothesis in phloem. CB will be more useful here. Be sure to include the concept of solute movements and gradients, hydrostatic pressure, bulk flow caused by the hydrostatic pressure and the incompressibility of water. Include in your answer Fig. 36.17 and its notation on pg. 764 in CB.

Answer Data-based questions: Explaining water movement BCC pg.415. Reading CB pg. 750-752 ‘Differences in water potential drive water transport in plant cells’ may help in answering this data-based question.

Applications and skills:

  • Application: Structure-function relationships of phloem sieve tubes.

Use BCC pg. 415-16 ‘Phloem sieve tubes’ to create a T table with the columns structure and function. In the left column write the structural feature of the phloem sieve tube and in the right column write how that structural feature aids the function of the cell.

Answer the questions to the Activity in BCC pg. 416 on the micrograph of phloem tissue.

  • Skill: Identification of xylem and phloem in microscope images of stem and root.

Read and examine the figures shown in BCC pg. 420-421 under ‘Identifying xylem and phloem in light micrographs’.

Identification of these tissues will occur using microscopes in September.

  • Skill: Analysis of data from experiments measuring phloem transport rates using aphid stylets and radioactively-labelled carbon dioxide.

Write out the nature of science statement taken from the syllabus.

Use BCC pg. 417 and CB Fig. 36.18 on pg. 764 to outline how aphid stylets can be used to measure the rate of transport in phloem.

Answer the Data-based questions on pg. 418 of BCC.

Use BCC pg. 419 ‘Radioisotopes as important tools in studying translocation’ to make a note describing how radioactively-labelled carbon dioxide can be used to measure the rate of translocation.

Answer the Data-based questions: Radioactive labelling (1) and (2) in BCC pg. 419-20

9.3 Growth in plants

Understandings:

  • Undifferentiated cells in the meristems of plants allow indeterminate growth.

Use BCC pg 422 ‘Growth in plants’ and CB pg 729 ‘Meristems generate cells for new organs throughout the lifetime of a plant: an overview of plant growth’ to explain the indeterminate growth of plants. Be sure to include both apical and lateral meristems.

  • Mitosis and cell division in the shoot apex provide cells needed for extension of the stem and development of leaves.

Use BCC pg. 423 ‘Role of mitosis in stem extension and leaf development’ and summarize the information under this heading. Draw and label Figure 1 ‘Structure of a shoot apical meristem’.

  • Plant hormones control growth in the shoot apex.

Use BCC pg. 424 ‘Plant hormones affect shoot growth’ to explain the role of auxin in the growth of the shoot apex. The effect of auxin and cytokinins on axillary bud development should be discussed.

Answer the Data-based questions: The acid growth hypothesis in BCC pg. 424-5

  • Plant shoots respond to the environment by tropisms.

Read CB pg.806-7 ‘Research on how plants grow toward light led to the discovery of plant hormones’.

Use BCC pg. 425 ‘Plant tropisms’ to discuss the tropic response of stems to light and gravity.

  • Auxin influences cell growth rates by changing the pattern of gene expression.

Use BCC pg. 425 ‘Auxin influences gene expression’ to explain the effect of phototropins, transcription of PIN3 proteins (auxin efflux pumps) and auxin on cell growth rates.

  • Auxin efflux pumps can set up concentration gradients of auxin in plant tissue.

Use CB pg. 809-10 ‘Auxin’ and ‘The Role of Auxin in Cell Elongation’ and BCC pg. 426 ‘Intracellular pumps’ to explain how PIN3 proteins (efflux pumps) and auxin can produce phototropism. Include in the discussion the acid growth hypothesis and the role of expansins. Also explain gravitropism in roots based on the uneven distribution of auxin by efflux pumps.

Applications and skills:

  • Application: Micropropagation of plants using tissue from the shoot apex, nutrient agar gels and growth hormones.

Use BCC pg. 427 ‘Micropropagation of plants’ to outline what micropropagation is and the steps involved.

  • Application: Use of micropropagation for rapid bulking up of new varieties, production of virus-free strains of existing varieties and propagation of orchids and other rare species.

Use BCC pg.427-8 ‘Micropropagation is used for rapid bulking up’ to outline the 3 uses of

Nature of Science:

  • Write the nature of science statement in your notes from the syllabus.
  • Make a summary of BCC pg. 428 ‘Genomics has improved understanding of the role of plant hormones’ to discuss the use of microarrays in research on gene expression.

9.4 Reproduction in plants

Understandings:

  • Flowering involves a change in gene expression in the shoot apex.

Read CB pg. 818-819 ‘The Phytochrome Switch and Seed Germination’ and pg. 821-22 ‘Photoperiodism synchronizes many plant responses to changes of season’ for more detailed background. Then use BCC pg. 429-30 ‘Flowering and gene expression’ to explain how plants move from the vegetative to reproductive phase using phytochrome, FT gene, FT mRNA and FT protein.

  • The switch to flowering is a response to the length of light and dark periods in many plants.

Use BCC pg. 430 ‘Photoperiods and flowering’ and the background reading from CB above, to explain how flowering occurs in long-day and short-day plants using PR and PFR as a biological clock.

Answer Data-based questions: Sowing times for soybeans in BCC pg. 430-1

  • Most flowering plants use mutualistic relationships with pollinators in sexual reproduction.

Use BCC pg. 432’Mutualism between flowers and pollinators’ and summarize the information under this heading

Answer Data-based questions: Factors affecting pollen development in BCC pg. 432-3

  • Success in plant reproduction depends on pollination, fertilization and seed dispersal.

Use BCC pg. 432 ‘Pollination, fertilization and seed dispersal’ and CB pg. 784 Fig. 38.1to distinguish betweenthese 3 terms and outline their role in successful plant reproduction.

Applications and skills:

  • Application: Methods used to induce short-day plants to flower out of season.

Use BCC pg. 431 ‘Inducing plants to flower out of season’ and summarize the information under this heading.

  • Skill: Drawing internal structure of seeds.

Use BCC pg. 434 to draw and label the internal structure of the bean (Phaseolus vulgaris) seed. Summarize the information accompanying the drawing.

  • Skill: Drawing of half-views of animal-pollinated flowers.

Use CB pg. 785 Fig. 38.2 and BCC pg. 431 ‘Draw an animal pollinated flower’ to draw and label an animal-pollinated flower. Be sure to include the labels for the carpel and stamen. Summarize the information accompanying the drawing.

  • Skill: Design of experiments to test hypotheses about factors affecting germination.

Use BCCpg. 435 ‘Germination experiment design’ to describe the events in the seed required for germination. Write answers to the 4 bulleted decisions that need to be made for the design of an experiment.

Answer Data-based questions: Fire and seed dormancy in a plant of the chaparral in BCC pg. 436

Nature of Science:

  • Write the nature of science statement in your notes from the syllabus.
  • Use BCC pg. 433-4 ‘Preserving habitats as a conservation measure’ to summarize the information under this heading.

HOORAY!! Plants unit done. Enjoy the rest of summer!!