Unit 5: Plant Organisms

Types of Tropisms

Phototropism: Growth of plant in response to light

Geotropism: Growth of plant in response to gravity

Thigmotropism: Growth of plant in response to touch

Small Responses

Causes plant to bend to stimulus

Regulated by plant hormones

Rapid movement in response to stimulus

Quickly Reversable

Caused by movement of water/ions in/out of cells

Increases/decreases turgor pressure of the mesophyll cells

Flooding: Lack of oxygen for cellular respiration

Response: Partial roots above ground

Drought: Less water taken in than used

Response: Fleshy stem/leaves (holds water)

Response: Modified leaves (spines/needles)

Response: Thick cuticle and epidermis

Response: Stomata in pits surrounded by hairs

Salt: Roots lose water to soil through osmosis

Halophytes Response: Specialized glands pump salt across leaf epidermis for rain to wash away

Halophytes Response: Pump salt to stems at tip of plant; sheds tips to remove salt

Parenchyma = thin walled/living

Collenchyma = thick walled/living

Sclerenchyma = lignin in cell walls/dead

Role: Cellular growth, Storage, Support/Protection

Xylem: Thick cell walls, dead at maturity

Phloem: Thin cell walls, living at maturity

Role: Transport of nutrients and support

Epidermis and Dermis Cells

Role: Protection

Outermost cell layers

Thick Cell Walls

Wxy cuticle

Apical meristems (Tips of Roots/Shoots)

Lateral meristems or Cambium

Role: Plant growth; regions that are immature and continue to divide (meristems)

Function

Transportation of nutrients/oxygen

Raise/support leaves/reproductive organs

Specialized stems

Rhizomes: store wate/food to help survive winter

Tubers: Underground stems

Bulbs: Tiny, underground stems

"On Ground": Grow along soil

Types of Stems

Herbaceous: Green/soft; don't last winter

Woody: Hard/tough (wood); last winter

Vascular cambium: Allows for thicker stem growth

Sapwood: Younger Xylem (transport)

Heartwood: Olderer Xylem (support)

Bark: Everything outside Vascular cambium (protection)

Dicots V.S Monocots

Spring wood: thin walls; light colour
Xylem produced rapidly

Summer Wood: thick walls, dark colour
Xylem produced slowly

Function

Anchor Plant

Absorb Water/Nutrients

Some Store Food

Transport water/nutrients to stem

Types of roots

Epidermis: Outer layer, Protects inside/absorb nutrients

Epidermis: Middle cell layer, Stores starch

Root Hairs: Increase SA to absorb more nutrients

Endodermis: Wax layer;Separates cortex and vascular cylinder

Vascular cylinder: Contains plants conducting tissues
(xylem and phloem)

Function:provides nutrients to embryo and becomes first leaf

Seed Coat: Tough coat for protection

Endosperm: Nutrient rich, food for embryo

Seed Dispersal

Conditions for Germination

Moisture: After heavy rain

Temperature: To activate enzymes

Oxygen: to carry out cellular respiration

Light: For photosynthesis

Dormancy – resting period

Absorption of water by the seed

Embryo releases growth hormone

Triggers cotyledons to convert starch to maltose

Maltose is used for cellular respiration

Sugar content is increased, causing more water to be absorbed

Seed coat softens and embryo emerges

Epidermal cells (outside): covered in waxy cuticle

Mesophyll cells (middle): contain chloroplast

Paliasids:closely packed, upper layer

Spongy: loosely packed, loosely packed for gas exchange, bottom layer

Stoma:gas passes in or out

Guard cells: control opening and closing of stoma

Function

Defense

Photosynthesis

Gas exchange

Types of leaves

Dicots: Branching, Petiole

Monocots: Parallel, Leaf sheet

Sepals:Covers and protect flower buds before blossom opens

Petals: Colourful to attract pollinators

Stamen: Male Reproductive Organ

Filament:Connects Anther to flower

Anther: Produces pollen grain (Male Gametes)

Pistil: Female Reproductive Organ

Stigma: Sticky tip to collect pollen grain

Ovary:Contains ovule (female gamete)

What is it?

Transports water/minerals from roots to stem/leaves

Long, hollow tubes formed by non-living cells

Types of Xylem

Trachiod: Long,Narrow; Trapid at ends

Vessel Elements:long, wide; joined together; more efficient

What is it

Living Tissue

Transports sugar through the plant

Sieve tubes

Long, hollow tubes

Between are sieve plates (large pores to facilitate transport)

Companion cells that direct activities and supply nutrients

About transportation

Source: Cells with high concentration of sugars

Sink: Cells with low concentration of sugars

Sugars can move up/down (Nutrients moves only up)

1. Source to Pholem

Active transport of sugars across cell membrane

Water moves from xylem to phloem when high concentration of sugar through osmosis

Translocation moves sugars from phloem cell to phloem cell

Not Well Understood

3. From phloem cells to sink cells

Passive transport: High concentration of sugar in phloem, low in sink

Water re-circulated into xylem

Root Hairs

Increase SA to absorb more nutrients/water

Form symbiotic association with fungi (mycorrhizae)

Water (Osmosis)

Cytoplasm has less water than soil

Water moves to vascular cylinder

Nutrients (Active Transport)

From low concentration (outside cell) to higher concentration (inside cell)

Water molecules and dissolved nutrients called xylem sap

Xylem sap rises due to root pressure and capillary action

Root pressure: Osmotic force pushes xylem sap upward

Capillary Action: Water rise because of attractive forces between water molecules and side of wall

3. Transport into Leaves

Evaporation of water through the stomata of plant leaves

Factors Affect Transpiration

Temperature: High transpiration rate in high temperature

Light: High transpiration rate during day since stomoa is open

Humidity: High transpiration rate in low humidity

Wind – High transpiration rate
in high winds

Number of Stomata per Leaf Surface Area: More stomata = Higher transpiration rate

Leaves are main driving force of xylem upward