Plant Organs - PowerPoint PPT Presentation

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Plant Organs

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Plant Organs Roots & Stems – PowerPoint PPT presentation

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Title: Plant Organs


1
Plant Organs
  • Roots Stems

2
I. Roots
  • A. F(x)s grow underground
  • 1. Absorb water nutrients from soil
  • 2. Anchor plant in the soil
  • 3. Make hormones important for growth
  • development

3
I. Roots
  • B. Structure
  • 1. Root cap
  • F(x) protects apical meristem

4
I. Roots
  • B. Structure
  • 2. Root hairs
  • F(x)
  • increase surface area for absorption

5
I. Roots
  • B. Structure
  • 3. Casparian Strip
  • F(x)
  • channel water
  • dissolved nutrients into vascular tissue
  • allow movement only into roots

6
I. Roots
  • C. Types of Roots
  • 1. Taproots
  • a. Large main root that can store food
  • b. F(x) absorption,
  • anchoring
  • E.g.

beet
carrot
7
C. Types of Roots
  • 2. Fibrous roots
  • a. Numerous small roots
  • b. Grow near surface
  • c. F(x) absorption,
  • anchoring
  • c. E.g. grass

8
C. Types of Roots
  • 3. Prop or
  • Adventitious roots
  • a. Grow down to soil from stem,
  • above ground
  • b. F(x)s support,
    absorption
  • c. E.g. corn,
  • banyon tree

9
C. Types of Roots
  • 4. Aerial Roots
  • a. Grow without soil,
  • in air
  • b. F(x) absorb water from moist air
  • c. E.g. orchids in tropical
    rainforest

10
II. Stems
  • A. F(x)s
  • 1. Hold leaves up to sunlight
  • 2. Transport water nutrients from roots to
    leaves
  • 3. Food storage in some plants

11
II. Stems
  • B. Stem Structures
  • 1. Node place where
  • one or more leaves are
  • attached
  • Note At the point of attachment of each leaf,
  • there is a lateral bud with
  • an apical meristem
  • capable of developing
  • into a new shoot

12
II. Stems
  • B. Stem Structures
  • 2. Internode
  • part of stem
  • between nodes

13
II. Stems
  • C. Specialized stems
  • 1. Rhizome horizontal underground stem
  • 2. Tuber
  • Underground stem w/ buds
  • Food storage
  • E.g. potato, parsnip

14
II. Stems
  • C. Specialized stems
  • Bulb
  • large bud w/ layers
  • Food storage
  • Many edible
  • E.g. onion, garlic

15
II. Stems
  • C. Specialized stems
  • 4. Corm
  • Upright, thickened underground stem
  • Food storage
  • Not usually edible
  • E.g. shamrock plant (Oxalis)

16
II. Stems
  • C. Specialized stems
  • 5. Some plants almost
  • all stem,
  • no leaves
  • E.g. cactus

17
II. Stems
  • D. Stem growth
  • 1. Growth in Length only at tips of stems
    where new primary growth occurs via apical
    meristems
  • 2. Growth in Circumference
  • width via
  • lateral meristems

18
II. Stems
  • E. Primary Growth in Stems
  • 1. Vascular tissue arranged in
  • vascular bundles
  • 2. Dicots bundles in a ring around
    outside edge
  • 3. Monocots bundles scattered throughout
    stem

19
II. Stems
Dicot stem CS
Vascular bundles
20
II. Stems
  • E. Primary Growth in Stems
  • 4. Pith center of the stem
  • 5. Cortex ground tissue btwn.
  • Vascular Bundles epidermis

Vascular bundle
monocot
dicot
21
II. Stems
  • F. Secondary Growth in Stems
  • Which get wider year after year,
  • monocots or dicots?
  • DICOTS!
  • Most monocots have no secondary growth.
  • 1. ?stem width in dicots due to cell in
  • vascular cambium

22
II. Stems
  • 2. Vascular Cambium arises in vascular bundle
    btwn. xylem phloem
  • 3. Cylinder formed by cambium,
  • then secondary xylem inside,
  • then secondary phloem on outside of cylinder

23
II. Stems
  • G. Woody Stems
  • 1. Heartwood
  • 2. Sapwood
  • 3. Bark
  • DRAW THIS!

24
II. Stems
  • G. Woody Stems
  • 1. Heartwood
  • Dark color
  • Center of tree trunk
  • Dead xylem , no longer transports water
  • F(x)
  • support

25
II. Stems
  • G. Woody Stems
  • 2. Sapwood
  • Lighter in color
  • Nearer to outside of tree trunk
  • F(x) transport (live xylem)
  • Note In a large diameter tree, heartwood gets
    wider, sapwood stays relatively same width

26
II. Stems
  • G. Woody Stems
  • 3. Bark
  • F(x) protection
  • Made of cork, cork cambium phloem

27
II. Stems
  • H. Stem F(x)s
  • 1. Phloem moves sugars
  • a. Translocation sugars moved from
    source (photosynthesis in leaves)
  • to sink (where they are stored)
  • b. Products of Photosynthesis can move
  • in ____?___ direction
  • ANY

28
II. Stems
  • H. Stem F(x)s
  • 1. Phloem moves sugars
  • c. Pressure Flow Hypothesis
  • i. Sugars PUMPED into sieve tubes
  • _at_ the source
  • ii. Turgor pressure increase due to water
    entering sieve tubes by osmosis

29
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30
II. Stems
  • H. Stem F(x)s
  • 2. Xylem moves water nutrients
  • a. Cohesion-Tension Theory
  • combination of 3 processes
  • i. Transpiration
  • ii. Cohesion
  • iii. Adhesion

31
Transpiration
  • In leaves, release of excess water to atmosphere
  • Creates negative pressure in xylem
  • Replacement water pulled from xylem
  • Water enters roots to replace lost water

32
Cohesion
  • Water molecules stick to each other pull each
    other up narrow xylem tubes
  • Water is a polar molecule, therefore
  • Water molecules attract each other!

33
Adhesion
  • Water molecules strongly attracted
  • to xylem wall

34
II. Stems
  • b. Final words on water movement in plants
  • i. Varies with time of day
  • ii. Midday stomata open, rapid movement
  • iii. Night stomata closed movement stops
  • Exception cacti stomata open _at_ night
  • Why?
  • to minimize water loss
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