1. Roots, Stems, & Leaves

2. Roots 2 Main Types: Tap Roots Fibrous roots
long & thick primary root with small secondary roots
Found in dicots like oaks, carrots, beets, dandelions
Fibrous roots
Branching with no single larger root
Mainly found in monocots
Extensive root systems help prevent topsoil erosion

3. Root Structure & Function
Structures:
Epidermis - both protects and absorbs
Root hairs - penetrate soil & provide larger surface area for absorption
Cortex - Ground tissue between epidermis & vascular cylinder
Endodermis - layer that surrounds vascular cylinder

4. Function
Roots anchor the plant in the ground and absorb water & dissolved minerals from soil

6. Leaves Characteristics: Main organs of photosynthesis
Blade – thin, flattened sections for collecting sunlight
Petiole – stalk which attaches blade to stem

8. Guard cells
One of the paired epidermal cells that control the opening and closing of a stoma in plant tissue.

9. Stems Functions: Produce leaves, branches, & flowers
Hold leaves up to sunlight
Transport substances between roots & leaves

10. Stem Structure Stems are composed of dermal, vascular, & ground tissue
Nodes - where leaves are attached
Internode - regions in between nodes
Buds - undeveloped tissue that can produce new stems & leaves; found where leaves attach to nodes

11. Specialized Stems Stems that store food and can remain dormant
for a time
Tuber – usually grows underground, stores food (potato)
Bulb – central stem surrounded by short, thick leaves (onion)
Corm – similar to bulb but stem is thickened to store food (gladiolus flower)
Rhizome – horizontal underground stem that can form new shoots (ginger)

12. Plant Adaptations & Plant Tropisms

13. Plant Adaptations
Dormancy – period during which growth & activity decrease or stop

14. Plant Adaptations Aquatic plants must tolerate mud nearly
devoid of oxygen
Tissues with air-filled spaces for O2 to diffuse
Seeds often ­ float and grow quickly

15. Plant Adaptations Xerophytes - desert plants
Root systems spread out for long distances
Leaves may be reduced to spines; photosynthesis occurs in stems, which also store water

16. Plant Adaptations Carnivorous plants – live in bogs with little
nitrogen
Use specialized leaves to trap & digest insects to meet nutritional needs
Pitcher plants - drown insects in specialized leaves
Sundews - trap insects with sticky secretions
Venus’ flytrap - has leaves that snap shut

17. Plant Adaptations Parasites & Epiphytes – extract water &
nutrients from a host plant
Parasites harm the host
Epiphytes grow on bodies of other plants but gather their own water & produce their own food
Ex: Spanish moss, bromeliads, many orchids

18. Plant Adaptations Chemical defenses – manufacture poisons,
insect hormones, etc. that effect
animals/insects

19. Plant Tropisms
Plant Tropisms - responses of plants to external stimuli
Gravitropism – stems grow up & roots grow down
Phototropism – plants grow toward light
Thigmotropism – response to touch – vines & climbing plants wrap around support structures

20. Plant Hormones 1. Auxins – cause of phototropism
Stimulate cell elongation
Higher concentration on shaded side of the plant causing stem to elongate and bend
-- Cause of gravitropism
higher concentration on lower part of root stem inhibit cell growth, causing root to grow downward.
Help move root through the soil and around objects in the soil

21. Plant Hormones
2. Cytokinins – produced in growing roots and in developing fruits and seeds.
Cause dormant seeds to sprout
Cells grow thicker
3. Gibberellins – growth promoting
Increase size of stems and fruits
4. Ethylene – stimulates fruit to ripen