1. Plant structure and growth
Topic 9.1

2. Assessment Statements
Draw and label plan diagrams to show the distribution of tissues in the stem and leaf of a dicotyledonous plant.
Outline three differences between the structures of dicotyledonous and monocotyledonous plants.
Explain the relationship between the distribution of tissues in the leaf and the functions of these tissues.
Identify modification of roots, stems, and leaves for different functions: bulbs, stem tubers, storage roots, and tendrils.
State that dicotyledonous plants have apical and lateral meristems.
Compare growth due to apical and lateral meristems in dicotyledonous plants.
Explain the role of auxin in phototropism as an example of the control of plant growth.

3. Review of land plants Plant group Major features
Non-vascular land plants
no conducting tissue
often grouped together as bryophytes
usually small and grow close to the ground
include mosses, liverworts, and hornworts
Seedless vascular plants
well-developed vascular tissue
do not produce seeds
include horsetails, ferns, club mosses, and whisk ferns
Seeded vascular plants
most living plants are in this group
seeds contain an embryo, a supply of nutrients, and a protective outer coat
have extensive vascular tissue and include some of the world’s largest organisms

4. Seeded vascular plants
Gymnosperms – have seeds that do not develop within an enclosed structure
Angiosperms – have seeds that develop within a protective structure

5. Angiosperm Tissue type Description Dermal tissue
outer covering which protects against physical agents and pathogenic organisms
prevents water loss and may have specialized structures for various purposes
Ground tissue
consists mostly of thin-walled cells that function in storage, photosynthesis, support, and secretion
Vascular tissue
xylem and phloem carry out long-distance conduction of water, minerals, and nutrients within the plant and provide support

6. Meristematic tissue All 3 tissue types derive from meristematic tissue
Composed of aggregates of small cells that have the same function as stem cells in animals
When these cells divide, one cell remains meristematic (initial) while the other (derivative) is free to differentiate and become part of the plant body

7. Root tissue Absorbs mineral ions and water from the soil
Anchor the plant
Provide food storage
epidermis
cortex
xylem
endodermis
phloem

8. Stem tissue Plant region where leaves are attached
Area where leaf joins is called a node and the area between two nodes is called the internode

9. Leaf tissue Involved in photosynthesis
Upper epidermis
Involved in photosynthesis
Consist of the blade and a stalk called the petiole that attaches the blade to the stem
Cuticle (wax)
Palisade mesophyll
xylem
Spongy mesophyll
phloem
Vascular bundle
Stomatal pores

10. Functions of tissues in relation to their position in the leaf
The palisade mesophyll is located in the upper portion of the leaf where light is most available. The cells of this region are chloroplast rich, thus allowing for maximal photosynthesis.
Veins are distributed throughout the leaf so as to transport raw materials and products of photosynthesis. The veins occur roughly in the middle of the leaf so as to be near all cells.
The spongy mesophyll is located just superior to the stomata allowing continuous channels for gas exchange.
The stomatal pores are on the bottom of the leaf. This area receives less light with a resulting lower temperature. The lower temperature minimizes water loss from the pores and the plant.

11. Monocotyledonous and dicotyledonous plants
Monocots
Dicots
Parallel venation in leaves
Netlike venation pattern in leaves
3 flower parts or multiples of 3
4 or 5 flower parts or multiples of 4 or 5
Seeds contain only one cotyledon (seed leaf)
Seeds contain two cotyledons (seed leaves)
Vascular bundles arranged throughout the stem
Vascular bundles arranged as a ring in the stem
Root system mainly fibrous
Root system involves a taproot (main root)
Pollen grain with one opening
Pollen grain with three openings

12. Leaf venation

13. Flowers

14. Embryos

15. Stems

16. Roots

17. Pollen

18. Roots Root modification Description and example Prop roots
Thick adventitious roots that grow from the lower part of the stem and brace the plant (ex: corn)
Storage roots
Specialized cells within the root store large quantities of carbohydrates and water (ex: carrots and beets)
Pneumatophores
(air roots)
Produced by plants that live in wet places, these roots extend above the soil or water surface and facilitate oxygen uptake (ex: mangroves)
Buttress roots
Large roots that develop near the bottom of trees to provide stability (ex: fig tree)

19. Prop, storage, pneumatophore, or buttress?

20. Stems Stem modification Description and example Bulbs
Vertical, underground stems consisting of enlarged bases of leaves that store food (ex: onions)
Tubers
Horizontally growing stems below ground that are modified as carbohydrate-storage structures (ex: potatoes)
Rhizomes
Horizontal stems that grow just below the surface to allow plant spreading (ex: ginger plant)
Stolons
Horizontal stems growing above ground that allow a plant to reproduce asexually (ex: strawberry plants)

21. Bulb, tuber, rhizome, or stolon?

22. Leaves Leaf modification Description and example Tendrils
Structures that coil around objects to aid in support and climbing (may also be formed from modified stems) (ex: pea plants produce tendrils from leaves)
Reproductive leaves
Produce tiny plants along the leaf margins that fall to the ground and take root in the soil (ex: kalanchoe plants)
Bracts or floral leaves
Coloured modified leaves that surround flowers and attract insects for pollination (ex: poinsettia)
Spines
Reduce water loss, may be associated with modified stems that carry out photosynthesis (ex: cacti)

23. Meristems Plants show growth throughout their entire life
Continual pattern of growth is referred to as indeterminate
Some plants are annuals and complete their life cycle in one year
Other plants are biennials and take two years to complete their life cycle
Perennials live many years and when they die it is usually due to infection or some environmental factor
Reason for indeterminate growth is due to meristematic tissue

24. Dicot meristematic tissue: apical and lateral
Apical meristems
Occurs at tips of roots and stems
Produces primary tissues and causes primary growth which allows the root to extend throughout the soil
Allows stem to grow longer
Herbaceeous, non-woody stems and roots
Lateral meristems
Allow growth in thickness of plants
Woody plants
Two types
Vascular cambium produces xylem/phloem and secondary xylem which produces wood
Cork cambium produces cork cells of outer bark

25. Overview of primary and secondary growth

26. Phototropism
Tropisms are growth or movement responses to directional external stimuli
may be positive (towards stimulus) or negative (away from stimulus)
Common stimuli: chemicals, gravity, touch, and light
Phototropism means plant growth in response to light
Plant stems exhibit positive phototropism and roots demonstrate negative phototropism

27. Auxins
Auxins are plant hormones that cause the positive phototropism of plant shoots and seedlings
found in the embryos of seeds, the meristems of apical buds and young leaves
Work only on plant cells that have auxin receptors
Increase flexibility of plant which enables cell elongation on the side of the shoot necessary to cause growth towards the light
Auxin is redistributed to the stem side away from the light source causing a curvature toward the light source
Called indoleacetic acid (IAA)