Plant Physiology (Topic 10)

Shoot system

above ground

(stems, leaves, flowers, fruit)

Root system

below ground

(roots)

* anchors
* absorbs water
* storage of sugar

Root Functions

* Root hairs
* extension of roots
* increase SA
* increase efficiency of absorption from soil

Root Structure

* support leaves
* transport of sugar/water
* height

Stem Functions

* photosynthesis
* may help attract pollinators
* gas exchange

Leaf Functions

Dermal

Outer covering tissue system

Dermal Tissue Functions

* absorption of water (reduce water loss)
* minerals at root hairs
* defense
* reflect sunlight

Guard cells

* Specialized cells in shoots
* Control gas regulation/gas exchange
* Regulate stomata

Cuticle

Waxy covering

Epidermis

Single layer of tightly packed outer cells

Periderm/bark

Corky outer layer of woody stems/roots

Periderm

In woody plants, ________ (bark) replaces epidermis

* guard cells
* open & close stomata
* protection

Functions of leaves in DERMAL tissue system

* gas exchange
* protection

Functions of stems in DERMAL tissue system

* water absorption @ root hairs
* protection

Functions of roots in DERMAL tissue system

Trichomes

Hair-like structures

Guard cells

Regulate somata, specialized cells in shoots, gas exchange

Root hairs

water/ion absorption

Ground

Comprises most of plant’s tissue system

Basically, if it’s not dermal or vascular, it’s ______ tissue

Found in all parts of the plant

Dermal Tissue Functions

* metabolism
* storage
* support activities
* photosynthesis
* short distance transport

photosynthesis

Functions of leaves in GROUND tissue system

* sugar storage
* structural support

Functions of stems in GROUND tissue system

* “cortex”
* transports water via osmosis from root hair to vascular system
* storage

Functions of roots in GROUND tissue system

Vascular

plant’s transport system

Vascular Tissue Functions

Transports:

* water
* sugar
* hormones
* minerals
* structural support

Xylem

Conducts H2O & dissolved minerals upward from the roots

Phloem

Transport sugars from where made (mostly leaves) to where needed (usually roots & sites of growth)

Conducts sugars down from leaves

Transpiration

* Loss of water through evaporation at the leaf surface (stomata)
* This creates a (-) pressure and pulls water up


* Passive process
* Plant controls, opening & closing of stomata

Cohesion-Tension Hypothesis

(hypothesis)

* sun rises → photosynthesis → stomata opens → transpiration
* Creates tension-like soda straw
* H2O in stem xylem pulled into leaves
* H2O in root xylem pulled into stem

H2O movement through xylem

atmosphere

stomata

leaf mesophyll

leaf xylem

stem xylem

root xylem

root tissue

soil

Cohesion

H2O sticks to SELF with H bonds

Adhesion

H2O sticks to OTHER things with H bonds

Phloem

Vascular tissue in charge of transport and distribution of sugar & hormones

Translocation

* bidirectional movement
* H2O containing sugar flows @ pressure through the phloem
* As phloem fluid moves, sugars are deposited where they are needed
* Pressure decreases as fluid moves away from leaves & sugars are deposited
* moves source → sink
* active process (against pressure gradients)

Pressure-flow hypothesis

(hypothesis)

* explanation for movements of sugars in phloem
* suggests translocation occurs via pressure gradient
* H2O containing sugar flows @ pressure through the phloem
* at source: high pressure, sugar loaded into phloem
* at sink: low pressure, sugar removed from phloem

Plasmodesmata

* cytoplasmic connections
* allows molecules, ions to pass b/w cells
* important for plant transport

Indeterminate

Plants have _____________ growth

(growth that occurs throughout the plant’s life, not limited to a specific period)

Primary Growth

Upwards growth

(ex. apical meristems: at tips of roots & shoots)

Secondary Growth

Thickness

(ex. lateral meristems: in tips of roots & stems)

Tips

Plants grow in and out from ____

* cell elongation = phototropism
* leaf development
* differentiation of meristem into vascular tissue
* apical dominance
* weakens primary cell wall so it can stretch

Auxin promotes

* Agent Orange (synthetic)
* fruit development
* seeds produce

Auxin practical applications

* control of cell division (mitosis) & differentiation (of meristem into shoots & roots)
* promotes cytokinesis

Cytokinisis

Cytokinesis only

No effect on plant growth

Auxin only

Cells grow but do not divide

Cytokinesis & auxin at equal amounts

Grow & differentiate but not as a blob

Auxins > cytokinesis

Roots form

Auxins < cytokinesis

Shoots form