09 Plant Science (AHL)

Plant Science is one of my favourite topics for HL students as it is a real opportunity to link many of the core ideas of Biology together. Think of not just as a series of assessment statements to check off, but as a chance to revise everything you have learned so far.

Consider this diagram of germination. How many links across the syllabus can you make?

Germination – how many links can you make across the curriculum?

This image is adapted from a diagram at Click4Biology. For some of my suggestions of how this diagram alone represents over 20 links across the curriculum, click here: Bean there, done that…

Here is the Essential Biology document for the whole topic. Presentations are below.

9.1: Plant Structure and Growth

Key terms: monocotyledon, dicotyledon, xylem, phloem, meristem, cambium, leaf, vein vascular bundles, adventitious, tap roots, waxy cuticle, palisade layer, spongy mesophyll, guard cells, stomata, chloroplasts, photosynthesis, stems, leaves, tubers, tuberous roots, tendrils, apical, lateral, mitosis, growth, wood, auxin, hormone, tropism, phototropism, geotropism.

9.2: Transport in Angiospermophytes

Key terms: xylem, phloem, evaporation, cohesion, adhesion, transpiration, mass flow, diffusion, active transport, translocation, ion exchange, symport, cation, anion, mycelium, boundary layer, sink, source, root, leaves, abscisic acid, stomata, xerophyte, CAM.

9.3: Reproduction in Angiospermophytes

Key terms: photoperiodism, flowering, Pfr, Pr, hormone, germination, sepal, petal, anther, filament, stigma style, ovary, pollination, fertilisation, seed dispersal, testa, micropyle, embryo root, shoot, cityledon, gibberelin, amylase, starch, maltose, glucose,

Top links:

Click4Biology plant science page

North Harris College animations links


Life without bees? from David Suzuki’s blog.

And who can leave out this hillbilly-tastic video:

  1. assessment statement 9.1.3 says explain the relationship between distribution of tissues in the leaf and the functions of these tissues.
    the answer should be restricted to the following functions: absorbtion of light, gas exchange, support, water conservation, trasport….

    what structure helps support the leaf??? the rest of them are understandable, but the study guide doesn’t explain which structure aid’s in supporting the leaf?

    • Good point – the vascular bundles (xylem and phloem) support the leaf, especially when filled with water. Don’t forget also the structural support role of the cellulose in all cell walls.

  2. Last year, did the transport ppt include info on apoplastic and symplastic routes? It’s not in the assessment statements, but I’ve seen it covered in old IB questions. Has it been excluded from expected material at this point? I have not seen any recent IB questions that include it. Thank you again for these amazing study tools!

    • Hi Mrs Foley,

      I have not included apoplastic and symplastic in these presentations, as they are not in the subject guide. They might have appeared in past paper questions for the old guide.

      Good luck!


  3. Dear Mr. Taylor

    This website is fantastically useful! Please never take it down or retire.

    My students think you are a biology god….

    Thank you


    PS Leonie says: ich finde die seite super klasse, sie ist echt super nuetzlich!!!!
    Sie sind ein Biologie Gott und wir sind echt begeistert von ihrer Seite.
    Vielen Dank
    Leonie, Blake, Chazdog Alpha, Louisa 🙂

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