1. 9.1 Plant Structure and Growth

2. Fig. 29.1
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

3. The basic morphology of plants reflects their evolutionary history as terrestrial organisms that must simultaneously inhabit and draw resources from two very different environments:
Soil provides water and minerals
Air is the main source of CO2 and light does not penetrate far into soil.
Plants have evolved two systems: a subterranean root system and an aerial shoot system of stems and leaves.

4. Most angiosperms belong to either the monocots (65,000 species) or dicots (165,000 species) several other clades branched off before these.

5. 9.1.2 Outline three differences between the structures of dicots and monocots

7. 9.1.1 Draw and label plant diagrams to show the distribution of tissues in the stem

8. 9.1.1 Draw and label plant diagrams to show the distribution of tissues in the leaf of a dicot

9. 9.1.3 Dicotyledon Structure
Dicotyledon – angiosperm that produces two leaves from the original seed
Roots uptake H2O and minerals. Main root “tap root” has many offshoots
Stem divides to produce petioles that support the leaves. Also contains vascular tissue in bundles.

10. Axillary buds on the stem provide tissues for lateral growth of branches and leaves
Terminal bud contains structures for the growth and elongation of the main stem

11. Roots (dicot)- transverse section
Absorb mineral ions and water from soil
Anchor the plant
Sometimes used in food storage
Epidermis – outer surface that provides protection
Cortex- outer region of root that conducts water from soil to vascular tissue
Endodermis – tissue surrounding vascular tissue; acts as selective membrane

12. Xylem – vascular tissue that transports water
Phloem – vascular tissue that transports organic molecules
By branching and by root hairs, surface area of root is increased

13. Stem (dicot) – transverse section
Connect leaves, roots and flowers and contain vascular tissue for transportation
Epidermis may exchange some gas with enviro. but mainly for protection
Vascular bundle – contains tissues that transport substances around the plant.
Xylem portion also gives support, especially in woody plants

14. Cambium – cells that differentiate into xylem or phloem
Cortex – primarily supportive tissue, some storage
Pith – storage region; also provides support to the plant by turgor pressure
Turgor pressure - when cells take up water and this exerts pressure against the cell membrane

16. Leaf (angiosperm)
Cuticle – waxy upper layer that prevents loss of water from evaporation. Also helps deter herbivore and frost damage
Upper epidermis – support and protection
Palisade mesophyll – densely packed cells that contain many chloroplasts. Located in upper ½ of leaf where light is most intense

17. Spongy mesophyll – loosely packed cells
Spongy mesophyll – loosely packed cells. Provides main gas exchange surface. Must be close to stomata.
Stomata (stoma) – pores in underside of leaf that allow O2 to diffuse out and CO2 to diffuse in. Also water vapor will diffuse out (transpiration)
Guard cells on either side of the stomata control opening and closing
Lower epidermis – support and protection

18. Vascular bundles contain xylem and phloem tissue and spread out throughout leaf
Xylem brings water to replace losses during transpiration
Phloem transports the products of photosynthesis out of the leaf
Broad, thin leaves help maximize the photosynthetic ability of the leaf

19. Roots There are two main types of roots: taproot systems (dicots)
fibrous root systems (monocots)

20. 9.1.4 Identify modifications of roots
Prop Roots- thick roots that grow from the lower stem that brace the plant (e.g. corn)
Storage roots -large roots that store carbohydrates and water (e.g. carrots and beets)
Air roots- roots that extend above soil to aid uptake of oxygen, usually plants in wet places have them (e.g. mangroves)
Buttress roots – large roots that develop near the bottom of the tree to provide stability

21. Storage
Roots
Buttress Roots
Air Roots

22. 9.1.4 Identify modifications of Stems
Bulbs- vertical underground stems consisting of enlarged leaf bases that store food (e.g. onions)
Tubers –Horizontally growing stems below ground that are modified as carbohydrate storage structures (e.g. potatoes)
Rhizomes- horizontal stems that grow just below the surface to allow plant spreading (e.g. ginger plant)
Stolons – horizontal stems that grow above ground and allow a plant to reproduce asexually (e.g. strawberries)

23. Bulb
Tubers

24. 9.1.4 Identify modifications of Leaves
Tendrils- structures that coil around objects to aid in support and climbing (e.g. pea plants)
Reproductive leaves –produce tiny plants along the leaf margins that fall to the ground and take root (e.g. kalanchoe plants)
Bracts or floral leaves- colored leaves that surround flowers and attract insects for pollination (e.g. poinsettia)
Spines – reduce water loss, may be associated with modified stems that carry out photosynthesis (e.g. cacti)

25. Tendrils
Reproductive Leaves
                        
Floral Leaves
Spines

26. 9.1.5 State that dicots have apical and lateral meristems
Plants grow throughout their lifetime
This is called indeterminite growth (animals exhibit determinite growth)
Meristematic tissue serves to create new growth, it is a lot like a stem cell in animals, as it is able to develop into any type of plant tissue
Dicots have two types of meristem
Apical
Lateral

27. 9.1.6 Compare growth due to apical and lateral meristems in dicots
Apical meristems
Also called primary meristems
Occurs at the tips of roots and and stems
Allows roots to extend into soil and stems to grow taller
Results in non-woody stems and roots
Lateral meristems
Also called secondary meristems
Woody plants have active lateral meristems
Allow growth in the thickness of a plant
Results in woody stems and roots

28. Apical Meristems

29. Two types of Lateral Meristem
Cork cambium
Occurs within the bark of a plant
Produces the cork cells of the outer bark
Vascular cambium
Produces secondary vascular tissue (xylem and phloem)
Lies between the secondary phloem (on the outside) and the secondary xylem (on the inside)
Secondary xylem is a major component of wood

30. 9.1.6 Compare growth due to apical and lateral meristems in dicots

32. Tropism
A tropism is a growth or movement response to directional external stimulus
May be positive (toward) or negative (away)
Common stimuli include chemicals, gravity, touch, and light.
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33. 9.1.7 Explain the Role of Auxin in Phototropism
If an area is crowded with plants, or light is scarce, a plant would be benefitted most by growing or moving toward the light
Auxins are plant hormones that cause positive phototropism of plant shoots and seedlings
Auxins are found in seed embryos, meristems of apical buds, and young leaves