lecture 10: Plant Physiology Flashcards
What are the two systems in plants
root system & shoot system
describe the root system
- below ground
- absorption
- bringing water in
- stability
describe the shoot system
- above ground
- stems, leaves, flowers, and fruit
- photosynthesis, reproductive structures
what is the hierarchical orginization of plants
- cells
- tissues
- tissue system
- organs
- roots
- stems
- leaves
describe roots
- underground in soil
- anchor to ground
what are the functions of roots
- absorb minerals and water
- store carbs, sugar, starches, and other reserves, vegetables
what are root hairs
- thin extensions of root epidermal cells
- where water enters ( osmosis)
- primarily near tip of elongated roots
describe the stems
- plant organs bearing leaves and buds
- elongate and orient shoot to maximize photosynthesis
- elevate reproductive structures - increase pollen and seed dispersal
- photosynthesis, sometimes
describe the leaves
- main photosynthetic organ in vascualr plants
- capture light, gas exchange ( wide surface area, thin so light can pentrate hit chloroplasts, spines in cacti are defensive)
- photosynthesis
- may help attract pollinators
what is the dermal tissue system
- outer protective covering
- nonwoody plants ( epidermis, cuticle)
- wood plants ( periderm)
epidermis
single layer of tightly packed cells ( green non-woody plant)
cuticle
waxy coating- prevent water loss/ desiccation ( all land plants, not cells, layer of wax) -> protects against sun damage, herbavores)
periderm
- (bark) replaces epidermis, all plant epidermis, only some plants bark,
what are the functions of the dermal tissue
- defence, absorbtion
- reduce water loss, reflect sunlight, protect
- roots: absorption of water, minerals at root hairs
- leaves,stem: gaurd cells- specialized cells in shoots - gas exchange - open and close stomata, protection
ground tissue system
- most of plant ( mesoderm of plant)
- anything not vascualr or dermal
- between outside and transport parts
the ground tissue system included cells specialized for
- storage
- photosynthesis
- support
- short distance transport
-metabolism - ## storage
Vascular tissue system
- transports materials throughout plant body
- long distance transport: water, sugar, hormones, minerals
- xylem cells: strong, structural support ( looks like straws)
xylem
- conducts H20, dissolved minerals upwards from roots into atmosphere
- water and minerals: from roots -> sky
phloem
- transport sugars from where made (mostly leaves) to where needed ( usually roots and sited of growth)
- sugar and hormones around plant
water movement through xylem
- atmosphere
- stomata
- leaf mesophyll
- leaf xylem
- stem xylem
- root xylem
- root tissue
- soil
cohesion-tension hypothesis
- during photosynthesis, stomata open H20 leaves
- sun rises -> photosynthesis + evaporation _> stomata open -> transpiration
- water is pulled upwards
transpiration
- water leaving the plant, loss of water through evaopartion at the leaf surface
- negative pressure pulls water up
- passive process- No ATP involved
- plant can control this: opening and closing of stomata ( gaurd cells in epidermis regulate how fast water is moving)
cohesion
H20 sticks with H bonds
adhesion
H20 sticks to other things with H bonds (xylem is polar, water is polar)
describe cohesion tension
- h20 in stem xylem pulled into leaves
- h20 in root xylem pulled into stem
- creates a void, area of low pressure
- pulling, negative pressure
- cohesion, pulling water molecules- high pressure -> low pressure (adhesion between water and plant)
Phloem conducts dissolved sugar
- bidirectional movement - translocation (mechanism)
- moves source (surplus) -> sink (net demand)
- not constabt, always move
- phloem eating enscets are devestiating to plant, increase pressure, rob plant of suagar
sink
area of storage or metabloism
source
area with excess sugar
pressure- flow - hypothesis
- explanation for movements of sugars in pholem
- suggests translocation occurs via pressure gradient
- at source - high pressure - sugar loaded into phloem
- at sink - low pressure - sugar removed from phloem
plasmodesmata
- cytoplasmic connections
- allows molecules, ions to pass between cells, without PM or cell wall
- important for plant transplant
- no energy costs across membrane
indeterminate growth
- occurs throughout life of plant
- due to perpetually dividing unspecialized tissue
- depends on situation, not final form
- grow only at apical meristems ( at the tip)
1 degree growth
- increase length by adding more cells ( result of growth at the meristem)
- all plants have 1 degree growth
seq 1 degree growth
- plants grow up and down from tips
- enlogation
- bike tree
2nd degree growth
- increases girth (circumference) of plant
- lateral meristems - vascular and growth tissue , gain width
- only woody plants have 2 degree growth
hormones
internal chemical signal
plant hormone
growth regulators, may have multiple effects, stress ( no water no sunlight
what are auxins
1st planthormone discovered - affects phototropism
what are tropisms
directional growht responce to environmental stimulus - often due to hormones `
what are the directions of tropisms
positive - growth towards stimulus ( leads grow towardss light)
negative - grows away from stimulus ( root grows away from light)
seq phototropism
- light exposed - auxins produced
- triggers enlogation
- shade side enlogates -> plant bends towardss light
- light side- not effected
